Join us next week for a special Astronomy on Tap alongside with the Astroinformatics conference! Program below.
As seating at the venue is limited, registration for this event is mandatory. We encourage all guests to register early to secure their spot. Entry cannot be guaranteed for unregistered attendees once capacity is reached. REGISTRATIONS: https://t.rausgegangen.de/tickets/astronomy-on-tap-koln-2
Every month at 19:00 in Theatercafe Filmdose (Zülpicher Str. 39, 50674 Köln), Astronomy on Tap Köln brings you fun and enlightening talks in German and English! Join us to find what Astrophysicists are up to in solving the puzzles of the cosmos.
Make sure to show off your smarts in the exciting Pub Quiz. Winners get astronomy goodies from the European Southern Observatory, SOFIA and other cool telescopes, to take home!
Check-in now for free! or simply respond to this email with the no. of people you plan to bring to the event (not mandatory but helps us to make adequate arrangements)
Program 26.Feb 2026
“Der Weltuntergang” (auf Deutsch) by Dr. Volker Ossenkopf-Okada
Die Astronomie kann recht klar vorhersagen, was der Erde alles von außen droht. Der Vortrag zeigt auf, was uns recht sicher und was eher unwahrscheinlich betrifft.
” The unknown love life of stars.” (in English) by Anais Pauchet Stars are actually not just solitary bright spots in the sky.
The CRC1601visited the DLR again. Like in 2025, the visit was accompanied by a series of interesting talks, kindly organized by Alexander Rüttgers and Achim Basermann. Further details are can be found on the linkedIn-post of the DLR
An international team led by MPIfR researchers used data from the Atacama Large Millimeter/submillimeter Array (ALMA) to shed light on a central question of galaxy formation.
They discovered shock-heated gas in one of the most spectacular aggregations of galaxies in the distant Universe.
They found evidence that a giant elliptical galaxy may form through the rapid collapse of this infant galaxy cluster.
The existence of massive, elliptical galaxies in the early Universe has puzzled astronomers for two decades. An international team led by Nikolaus Sulzenauer and Axel Weiß from the Max Planck Institute for Radio Astronomy (MPIfR) used data from the Atacama Large Millimeter/submillimeter Array (ALMA) to shed light on this open question of galaxy formation. They studied one of the most spectacular galaxy aggregations, expected to be the birthplace of an elliptical galaxy, in great detail. The team discovered enormous, shock-heated tidal debris around a group of 40 galaxies rapidly falling toward a common center. Although fleeting on astrophysical time scales, extreme events like this might represent a hallmark phase for massive galaxy and galaxy cluster assembly in the early Universe. The results are published in the current issue of The Astrophysical Journal.
Clusters of young galaxies in the early Universe that later grow into large clusters are called protoclusters. This artist’s impression of the protocluster SPT2349-56 shows interacting galaxies of different shapes and sizes, and gas (orange) that is torn apart and heated by tidal forces. Due to its great distance from Earth, we see SPT2349-56 as it looked only 1.4 billion years after the Big Bang, when the Universe was 10% of its current age. [Image Credit: N.Sulzenauer, MPIfR]
Solving a Cosmic Mystery
A surprising observation has puzzled astronomers for two decades: Massive and evolved galaxies already existed just a few billion years after the Big Bang. Researchers expected to only find galaxies with young stars and ongoing star formation so early in the history of our Universe. Instead, there are many elliptical galaxies with older stellar populations and very little cold gas to form new stars. These observations pose a challenge to models of cosmological structure formation.
The group led by MPIfR astronomers now made a big leap in understanding these systems. “In a Universe where larger galaxies grow hierarchically through gravitational interactions and mergers of smaller building-blocks, some giant ellipticals must have formed completely differently than previously thought. Instead of slowly assembling mass throughout 14 billion years, a massive elliptical galaxy might swiftly emerge in just a few hundred million years. It can form through the collapse and coalescence of a major primordial structure, in the time it takes the Sun to orbit around the Milky Way’s center once”, explains Nikolaus Sulzenauer, PhD researcher at the MPIfR and University of Bonn, and first author leading the analysis. “We find that the structures with the very highest densities must have decoupled first from the Universe’s expansion at only 10% of the current cosmic age, and then rapidly assembled entire protoclusters.” The compression of gas sparks a cosmic firework, prodigiously bright as it is heated by star-birth activity. It is a beacon at far-infrared to millimeter wavelengths and thus accessible by observatories like ALMA and the Atacama Pathfinder Experiment (APEX).
Observing a Transformation
The team observed the cold gas and dust in the center of SPT2349-56, a protocluster seen just 1.4 billion years after the Big Bang and located in the southern constellation Phoenix. SPT2349-56 enables a rare glimpse of the first clusters, the main hubs of massive elliptical galaxies. “SPT2349-56 holds the record for the most vigorous stellar factory”, remarks Axel Weiß, who was also involved in the original discovery of SPT2349-56 with APEX. “In the center, we found four tightly-interacting galaxies forging one star every 40 minutes,” adds Ryley Hill from the University of British Columbia (UBC) in Canada. For comparison, it currently takes a whole year for three or four stars to form in the Milky Way.
“Importantly,” notes Sulzenauer “this galaxy quartet launches coherent giant tidal arms at 300 kilometers per second, stretching over an area much larger than the Milky Way. They glow intensely at submillimeter wavelength, their brightness boosted ten-fold by shock-waves exciting ionized carbon atoms. This bright emission allowed us to precisely measure the motion of gas in this gravitationally ejected spiral, resembling beads on a string encircling the protocluster core. To our surprise, clumps of tidal debris link to a chain of 20 additional colliding galaxies in the outer parts of the collapsing structure. This hints at a common origin. For the first time, we are witnessing the onset of a cascading merging transformation. Most of the 40 gas-rich galaxies in this core will be destroyed and will eventually transform into a giant elliptical galaxy within less than 300 million years – a mere blink of an eye.”
This radio image of the protocluster SPT2349-56 shows the intensity of ionized carbon (CII) emitted at a wavelength of 158 micrometers. Star symbols mark the centers of galaxies, while orange contours highlight the tidal arms around the inner region. These tidally ejected, galaxy-scale gas clumps are found to be ten times brighter than expected. The size of the Milky Way disk is shown at the same scale.] [Image Credit: N.Sulzenauer, MPIfR]
Understanding How Galaxy Clusters Form
Duncan MacIntyre and Joel Tsuchitori, two UBC undergraduate students and part of the team, ran detailed numerical simulations. These were essential to bridge observations of this protocluster collapse with previous studies of mature galaxy clusters. The striking match between the different types of objects, found at different cosmic times, might not just demonstrate the importance of simultaneous major mergers during massive galaxy formation. It may also help to explain how heavy elements (such as carbon) are heated and transported throughout the first galaxy clusters.
“While our findings offer exciting new insights into rapid elliptical galaxy assembly, the various interactions between the merger shocks, gas heating from the growth of supermassive black holes, and their effect on the fuel for star-formation, remain big mysteries,” remarks Scott Chapman of Dalhousie University. “It might be too early to claim a full understanding of the ‘early childhood’ of giant ellipticals, but we have come a long way in linking tidal debris in protoclusters to the formation process of massive galaxies located in today’s galaxy clusters.”
Additional Information
The following scientists affiliated to the MPIfR are coauthors of this publication: Nikolaus Sulzenauer, Axel Weiß, Amélie Saintonge
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Original Paper The Astrophyiscal Journal [DOI: 10.3847/1538-4357/ae2ff0]
In our upcoming paper, we further develop techniques to make realistic line intensity mapping (LIM) simulations using empirical galaxy catalogue data for observations from the Fred Young Submm Telescope (FYST). LIM provides aggregate signal from a wide beam measured over an expansive sky map area, capturing information from dim galaxies which we cannot otherwise resolve at high redshift (the epoch of reionisation, EoR, 6 < z < 20, ~13 billion years ago). Our simulations must therefore accurately incorporate the primary target line emission, the star-formation tracer [CII] 158µm at the end of the epoch of reionisation (3.5 < z[CII] < 8.2 for FYST’s 210-420GHz range), as well as the foreground CO and [CI] contaminant signal (0 < z < 6). Correspondingly, it is imperative to ensure that the catalogues forming our mock tomographic maps have appropriate completeness across the entire redshift range.
Our simulation catalogues are primarily based on data from COSMOS2020, using HST, Subaru, VISTA and Spitzer data which covers a 1.44deg² range up to z = 10. However, this data has known incompleteness at the low and high redshift ranges, so we must account for it via multiple extrapolation techniques. By calibrating using the in-depth CANDELS subsample, and fitting to the stellar mass function of the sample, we can make samples comparable to the latest JWST data from the COSMOS-Web pencil survey (see figure). From this robust mock catalogue we can test LIM techniques such as masking (see Karoumpis et al 2024, the science highlight 10.25), thereby providing an empirical backing to other simulations and their contaminant removal techniques. This also provides a framework for upcoming cross-correlation work, including cross-instrument cross-correlations, which we will cover later this year.
Das meiste Licht erscheint uns weiß, ist aber tatsächlich eine Mischung vieler verschiedener Farben. In unserem Workshop wirst du ein Handspektrometer bauen, mit dem du diese Spektrallinien sichtbar machen kannst. So wirst du selbst entdecken, wie unterschiedlich das Licht aus verschiedenen Quellen zusammengesetzt ist – von der Straßenlampe über dein Smartphone-Display bis hin zum Licht der Sonne. Bei uns im Köln-Bonner Sonderforschungsbereich Kosmische Entwicklung der Lebensräume massereicher Sterne werden Spektrallinien verwendet, die uns verraten, welche Elemente und Moleküle das Licht aussenden, um die Umgebungen von Sternen zu untersuchen. Diese beeinflussen maßgeblich die Entwicklung von Galaxien und sind deshalb der Schlüssel zum Verständnis der Ursprünge unserer Galaxie. Mach mit und entdecke, wie Licht nicht nur unser tägliches Leben prägt, sondern auch dabei hilft, das Universum zu entschlüsseln!
Leitung: Dr. Isabelle Breloy, Helen Kupfer & Annemarie Sich (Physikalische Institute, Mathematisch-Naturwissenschaftliche Fakultät)
Every month at 19:00 in Theatercafe Filmdose (Zülpicher Str. 39, 50674 Köln), Astronomy on Tap Köln brings you fun and enlightening talks in German and English! Join us to find what Astrophysicists are up to in solving the puzzles of the cosmos.
Make sure to show off your smarts in the exciting Pub Quiz. Winners get astronomy goodies from the European Southern Observatory, SOFIA and other cool telescopes, to take home!
Check-in now for free! or simply respond to this email with the no. of people you plan to bring to the event (not mandatory but helps us to make adequate arrangements)
Program 29.Jan 2026
“Raumfahrt im 21. Jahrhundert” (auf Deutsch) by Alexander Wojtczak
Angetrieben von neuen wissenschaftlichen, strategischen und kommerziellen Interessen, hat die Raumfahrt in den vergangenen Jahren wieder an Bedeutung gewonnen. Fortschritte in Bereichen wie Trägerraketen, Antriebssystemen und Satellitendesigns haben zu neuen Anwendungsfeldern und der Entstehung eines privatwirtschaftlichen Raumfahrtsektors geführt, welche einer breiteren Gruppe von Akteuren den Zugriff auf den Weltraum ermöglichen. Wir werfen einen Blick auf die Entwicklungen und Herausforderungen, welche dieses neue Weltraumzeitalter prägen.
” Rock around the clock: the epochs of the universe” (in English) by Jonathan Clarke In this talk Jonathan will give an overview of how the cosmos has evolved with time, how observational astronomers find these periods of cosmic history, and how theorists bridge these gaps.
With the University of Cologne involved, a powerful radio telescope is rising in Chile’s Atacama Desert to probe the origins of the universe
One of the world’s most powerful radio telescopes is being built in the Chilean Atacama Desert with the participation of the University of Cologne. Once assembled, it will be able to look back to the origins of our universe. Its construction in Germany, its assembly at an altitude of 5,600 metres, and the expected scientific results – a journey to the limits of what is possible.
By Jürgen Rees
The sun can sear the skin in minutes, and the air is so deprived of oxygen that breathing becomes more and more difficult with every step. Under these conditions, the engineers and technicians are dependent on additional oxygen and, for safety reasons, are not allowed to exceed their strenuous shift work by even a single minute. Working on the mountain to help build the telescope requires a sense of adventure: for every working day spent at this altitude, one day below 2,700 metres is mandatory, and workers are not permitted to stay on the mountain for more than 13 days at a time.
The highest construction site in the world is a challenge for humans and machines alike. Even powerful special lorries carrying the individual parts of the telescope, each weighing several tonnes, struggle to reach the 5,600-metre summit of Cerro Chajnantor in Chile, moving at a crawling pace. Some lorries require the assistance of even more powerful excavators to navigate the dusty, stony winding path.
In the middle of the world’s driest desert, the Atacama Desert in Chile, a gateway to the universe’s past is being created: In January 2025, the telescope – disassembled in its individual parts – began its journey to Chile: the components were carefully transported from the harbour in Wesel to Antwerp, where they were loaded onto a loose freight ship. After six weeks at sea and a week’s wait in the Chilean port of Antofagasta, the journey continued 450 kilometres by lorry to the Atacama Desert, and finally to the summit. This is where the difficult assembly work began, which is slowly approaching its goal. The commissioning of the telescope, the so-called “first light”, is planned for Summer 2026.
The telescope was designed, developed, and built by the CCAT Observatory, Inc., an international consortium including the University of Cologne, Cornell University, the University of Bonn, the Max Planck Institute for Astrophysics, and a Canadian university network. It is financed by the German Research Foundation and private sponsors such as Fred Young, an alumnus of Cornell University.
Seeing the oldest light in the universe
For Dr Ronan Higgins from the University of Cologne’s Institute of Astrophysics, this is an incredible moment that the scientist, originally from Ireland, has been waiting a long time for: “I am particularly pleased to see that the high-tech components of the telescope have survived the long journey from Germany to Chile in one piece and can now be assembled.” As deputy project engineer, Higgins is more familiar with the new high-performance telescope than almost anyone else. In the dry, thin and therefore transparent atmosphere, he and the many other scientists involved in the project hope to find answers to the big questions regarding the origins of our universe.
For example, the researchers want to observe the oldest light in the universe – an almost unimaginable 13.8 billion years old – which they hope will provide crucial information about the Big Bang and the birth of the first stars. But the scientists are not only interested in the past: How do stars and galaxies form today? Can cosmic background radiation be measured and does the telescope provide clues as to how so-called dark matter and dark energy have influenced the expansion of the universe? “One big question, for example, is why the rate of cosmic star formation keeps changing and is currently in decline,” says Professor Dr Dominik Riechers from the Institute of Astrophysics, lead of the German CCAT consortium and a board member of the project. ”If we grasp this development, we could understand how the universe is evolving.”
Why is this research taking place some 12,000 kilometres away from Germany – in Chile of all places? The Atacama Desert is the driest place on earth, with an annual average rainfall of only around one fiftieth of that recorded in Death Valley in the United States – one of the hottest and driest places in the world. The clear, low-water vapour air allows the radiation from space to pass through almost unhindered. “The large field of view of the Fred Young Submillimeter Telescope and the dry atmosphere allow for an unprecedented deep mapping of the sky,” says Riechers.
Old light is being stretched
The telescope is being realised by the Duisburg-based company CPI Vertex Antennentechnik. Their high-precision telescopes can be found all over the world, including in the Atacama Desert. Sven Kümmel, engineer at CPI Vertex, is also accompanying the final phase of construction on site: “It’s actually a total contradiction: on the one hand we have a high-precision telescope, on the other hand we have dirt, dust, wind, snow, and ice. That is a real challenge.”
The core of the telescope are two six-metre mirrors made of aluminium and carbon fibre. The mirror surface must be as accurate as possible so that it can look far into space with great accuracy. “We are talking about a tolerance of ten microns across each mirror – a human hair has a diameter of around eighty microns,” explains Ronan Higgins. The two wide-angle cameras CHAI and PrimeCam act as the ‘eyes’ of the telescope. They receive radiation in the so-called submillimetre range – light that has been travelling for billions of years.
What exactly is radio astronomy in the submillimetre range? In astronomy and physics, the term refers to submillimetre waves (also known as terahertz waves) with wavelengths between a few hundred micrometres and one millimetre, which lie in the range between microwaves and infrared. Many objects and processes in the universe that are of great interest, such as star formation, primarily emit radiation in the submillimetre range. That way, astronomers and astrophysicists can study both extremely cold objects – such as the dense clouds of interstellar gas and dust in which new stars form – and very distant objects in the early universe. In the latter case, the expansion of the universe has stretched the light from these distant objects so they are visible in the submillimetre range.
The waves can also penetrate dust clouds that are impenetrable to visible light. This enables the observation of areas of star formation and the investigation of the chemical composition of interstellar gas. Radio waves are therefore one of the few windows through which scientists can explore the entire universe from the ground.
Pushing the boundaries of physics
Of course, space offers an environment that is even more free of water vapour than the summit of Cerro Chajnantor. However, the location is ideal for the astronomy requirements of the FYST, as it is too large to be transported by rocket. Its location thus offers observation conditions that are as close as possible to those in space.
Submillimeter radiation, for example, originates from clouds of dust and molecules surrounding distant black holes and star-rich galaxies. “This is pushing the boundaries of physics,” says astrophysicist Higgins. FYST will be the most powerful telescope in the world for its mapping speed and sensitivity at its wavelength. It will detail star and galaxy formation from the earliest days of ‘cosmic dawn’ shortly after the Big Bang through ‘cosmic noon’, when most of today’s stars were formed, providing insight on cosmic inflation and gravitational waves from the very first moments of the Big Bang.
Besides the scientists, donor Fred Young is also certain that the effort is worthwhile: “Our world-class submillimetre telescope at, arguably, the best site in the world for its wavelength, will provide the basis for significant research by many astronomers for many years to come.”
In addition to the scientific findings that make the world and the universe a little easier to understand, technologies are emerging that have an impact far beyond astronomy. “After all, Wi-Fi, GPS, and digital cameras are all by-products of astronomical research,” Higgins reminds us.
Students at the University of Cologne are also benefiting from the development and construction of the high-tech telescope: They build receivers for the submillimetre radiation and help to precisely align the complex mirror. ”It’s this kind of experience that shapes the next generation of researchers,” says Higgins. In the case of world class telescopes, students generally get processed data to work with. In the case of FYST, however, they are involved in the entire process, including operating the telescope, getting and processing the data, and making science.
In the middle of next year, the big moment will arrive: after approximately seven years of construction, the telescope will look deep into space for the first time – ready to capture the oldest light in the universe.
The CCAT Consortium (Cerro Chajnantor Atacama Telescope) is responsible for building the instruments used on the Fred Young Submillimeter Telescope (FYST), as well as for observations, data analysis, and publishing the scientific results. The FYST will be a 6-meter diameter telescope designed to operate at submillimeter to millimeter wavelengths and located at an exceptional site at 5600 meters (18,400 feet) on Cerro Chajnantor overlooking the ALMA array. The novel optical design of FYST will deliver a high-throughput, wide-field of view telescope capable of mapping the sky very rapidly and efficiently. The high precision surface and superb site will allow routine access to the 350 micron observing window; during the best weather conditions, operations at 200 microns will be possible. The construction phase is expected to lead to first light in 2026.
The Public Observatory Cologne is a private institution which is run by the members of the “Vereinigung der Sternfreunde Köln e.V.” on a voluntary basis. This association of interested amateurs and amateur astronomers was founded in 1922 with the aim of disseminating basic astronomical knowledge to the public and promoting the training and further education of active amateur astronomers within the scope of the available possibilities.With the 60cm refractor “Cologne Large Telescope” (CLT) installed in 2012, the Volkssternwarte Köln operates the largest freely accessible telescope in North Rhine-Westphalia
Proplyds are young stars surrounded by gas and dust discs that lose material through internal and external photo-evaporation. Understanding their evolution requires measurements of gas masses and key timescales, obtained from spectrally resolved observations of the molecular and atomic gas.
We studied an isolated, globule-shaped object near the centre of Cygnus OB2, known as proplyd #7. Its nature is debated: it may host either a massive star with an HII region or a G-type T Tauri star. In both scenarios, a photo-evaporating disk inside a molecular envelope may be present. Using SOFIA OI 63 μm and CII 158 μm data, together with IRAM 30m CO observations and radio continuum at 5.9 GHz (left panel of the figure), we detected all lines across the source. The brightest OI emission (right panel) lies west of the embedded YSO (marked by a yellow star) and shows bulk emission near 11 km/s and a redshifted wing at 13 km/s.
The OI can trace either a photodissociation region (PDR) orshock-heated disc material. The KOSMA-tau PDR model reproduces theemission in the proplyd tail under a modest UV field, but not near theYSO, where strong lines, broader profiles, and a possible CO outflow point to a protostellar disc. Radio continuum data instead indicate a thermal HII region, consistent with a massive central star.
Proplyd #7 contains mostly molecular gas, with ~20 M⊙ of molecular and a few solar masses of atomic material. Its external photo-evaporation timescale (~1.6×10⁵ yr) is shorter than the free-fall time (~5.2×10⁵ yr), suggesting that little additional star formation could occur – consistent with numerical simulations.
The true nature of proplyd #7 is not yet revealed. Our study sets constraints on the timeline of the evolution of this object and highlights observational discrepancies. Upcoming NOEMA and further IRAM 30m observations will help to elucidate if we indeed observe a disc around a massive star within this object, a rare and remarkable finding.
Über einen vermeintlichen »Diamantring«, der an keinen Finger passt.
Der Nachthimmel dient schon lange als Inspiration für Musik der gefühlstriefenderen Art. Und tatsächlich: Es gibt Momente, in denen das Universum so wirkt, als habe es selbst eine heimliche Playlist. Kölner Astronom*innen haben im Sternentstehungsgebiet Cygnus X einen »Diamantring« untersucht. Ja, diamonds, wie bei Rihanna. Nur passt der Ring an keinen Finger, denn mit seiner Breite von zwanzig Lichtjahren liegt er mit Abstand auf Platz eins der Charts.
Dieser Ring leuchtet im infraroten Bereich »bright like a diamond« und hat natürlich eine dramatische Backstory. Einst war er eine prachtvolle kosmische Blase, aufgeblasen von einem Stern, der mindestens so viel Energie hatte wie Lady Gaga beim Super-Bowl- Auftritt. Doch dann – typisch Universe-Melodrama – ist die Blase geplatzt. Wörtlich. Gase entweichen, Form kollabiert. Übrig bleibt: ein kosmischer Ring.
Simon Dannhauer vom I. Physikalischen Institut erklärt es ohne jegliche Allüren: »Die Blase ist sozusagen ›geplatzt‹, weil Gase in die dünneren Bereiche der Umgebung entweichen konnten. So blieb lediglich die besondere flache Form übrig.« Ich sehe Mariah Carey vor mir, die zwischen Staub- und Gaswolken steht und haucht: »Like a star, youʼre shining in the sky…« Und der Ring so: Ja klar, aber bitte in Slow Motion. Denn er wächst mit gerade mal 1,3 Kilometern pro Sekunde – Schneckentempo für kosmische Verhältnisse.
Um dem Ganzen auf die Spur zu kommen, mussten die Wissenschaftler*innen mit SOFIA, einem fliegenden Observatorium in einer Boeing, über 13 Kilometer hoch steigen. Eine Art kosmischer Tourbus, mit den besten Instrumenten. Von dort oben sahen sie: Der vermeintliche »Diamant« im Ring – ein junger Sternhaufen – gehört eigentlich gar nicht dazu. Auch das noch: ein Weltraum- Sham! Er liegt ein paar hundert Lichtjahre davor, tut aber auf den Fotos so, als würde er zum Ring gehören. Alles eine Frage der Perspektive also.
Für Romantiker ist das natürlich ein kleiner Dämpfer. Kein echtes Schmuckstück, kein kosmischer Verlobungsring, nur Gas, Staub und optische Täuschung. Aber mal ehrlich: Wer braucht schon ein Tiffany- Schmuckkästchen, wenn das Universum uns ständig mit neuen Remixen aus »Stars Are Blind«, »Starlight« und »A Sky Full of Stars« versorgt?
Der »Diamantring« zeigt jedenfalls, dass selbst explodierte Blasen im All noch glamouröser aussehen als alles, was wir auf Erden je Glitzerndes in die Kamera halten. Und vielleicht ist das die eigentliche Botschaft: Im Weltall ist einfach jede*r ein Star – selbst dann, wenn man nur Staub ist, der ein bisschen hübsch im Licht funkelt.
Astronomers identify more than four hundred individual rings in the jet of the binary star system SVS 13 / publication in ‘Nature Astronomy’
A team of astronomers including a researcher from Cologne has captured the most detailed images ever taken of a jet launched by a young star. In astronomy, a jet is a narrow, rapid stream of particles and energy that is hurled into space by celestial objects ranging from black holes to young stars. The latest images show a series of delicate, ring-like structures that record violent outbursts of energy during the star’s early life. With these findings, the researchers have confirmed a theoretical model that has prevailed for decades. The study ‘Bowshocks driven by the pole-on molecular jet of outbursting protostar SVS 13’ was published in the scientific journal Nature Astronomy.
The team used the Atacama Large Millimeter/submillimeter Array (ALMA) for its measurements and focused on a fast-moving jet emerging from SVS 13, a binary system approximately 1,000 light years from Earth. The researchers captured high-resolution images that show hundreds of nested molecular rings. Each group of rings traces the aftermath of an energetic burst during the star’s infancy.
The results provide the first direct confirmation of a three-decade-old model of these jets and – like the annual rings of trees – allow the reconstruction of the chronological processes of star formation. They show how stars ‘feed’ on surrounding material during their formation, before expelling some of it explosively.
Gary Fuller, Professor of Astrophysics at the University of Manchester and, a member of the Global Faculty of the University of Cologne, also a project leader in the new Dynaverse Cluster of Excellence, is a co-author of the paper. He says: “ALMA has provided a level of precision we’ve never been able to achieve before. These images give us a completely new way of reading a young star’s history. Each group of rings is effectively a time-stamp of a past eruption. It gives us an important new insight into how young stars grow and how their developing planetary systems are shaped.”
Stars like the Sun form deep within dense clouds of gas and dust. In their earliest stages, they undergo energetic outbursts that heat and disturb the material around them. At the same time, they launch rapid, tightly collimated jets of gas, that play a crucial role in regulating how the star accumulates matter and how its surrounding disc – where future planets will eventually form – develops.
The team identified more than 400 individual rings in the jet from SVS 13, showing how its shape and speed change over time. Using this data, the researchers reconstructed the jet’s 3D structure in unprecedented detail – a technique they refer to as ‘cosmic tomography’.
They found that the youngest ring matches a bright outburst observed in the SVS 13 system in the early 1990s. This is the first time astronomers have been able to directly connect a specific burst of activity in a forming star with a change in the speed of its jet.
The project involved researchers from 16 institutions across eight countries. It was led by the Institute of Astrophysics of Andalusia (IAA-CSIC) in Spain. The new ALMA observations form part of a long-running project to understand how stars and planets form, building on earlier work from the US National Science Foundation’s Very Large Array (VLA), which first revealed the jets from SVS 13.
Media Contact: Professor Dr Gary Fuller Institute for Astrophysics +44 161 306 3653 fuller@ph1.uni-koeln.de
Figure: “Tomographic” view obtained by ALMA that reveals how the supersonic protostellar jet from SVS 13 interacts with the surrounding environment. In the background, an image taken by the Hubble Space Telescope (HST) shows the cavity carved out by the jet, together with the bluish glow of the Herbig–Haro objects 7–11, especially striking at optical wavelengths. Credits: Guillermo Blázquez-Calero, Mayra Osorio, Guillem Anglada. Background image credits: ESA/Hubble & NASA, Karl Stapelfeldt.
We are happy to invite you to our upcoming women’s networking event: “From Research to Reach.”
This event will feature UoC alumni who have transitioned from academia to the private sector. Together, we’ll discuss topics such as: * The importance of support systems and mentors; * Building a scientific identity outside academia; * Confidence and sense of belonging after career or life changes; * Fostering inclusion and creativity in the workplace; * Different concepts of “impact”.
Confirmed panel speakers: * Dr. Aleena Baby earned her PhD in Astrophysics from UoC in 2023 and has since transitioned to the private sector, working primarily in data science. She is currently a Data Scientist and AI specialist in Germany’s manufacturing industry, and a Lecturer at a technical university. Through her “Academia to Industry” brand, she also helps researchers and PhDs in navigating career transitions into industry roles.
* Dr. Annika Franeck completed her PhD in Astrophysics at UoC in 2018 before undertaking a postdoctoral position at the Czech Academy of Sciences. She later moved into industry as a Product Developer at BetterDoc. She is now a Team Lead Asset in Pricing & Analytics at Next Kraftwerke, contributing to the energy transition toward a sustainable future.
* Dr. Nassim Tanha, who obtained her PhD at the UoC in 2023, where she also worked as a postdoctoral researcher. She works as an ESG data manager at BarmeniaGothaer Asset Management since May of 2025.
Event duration: Approx. 2 hours.
This event is intended for all non-male SFB 1601 members.
📅 Date: December 12 🕔 Time: 17:00 📍 Location: SR ETP 0.02 🥪 Food and drinks will be provided.
To help us plan catering, please RSVP here by December 8 if possible:
New observations made with the ERIS instrument at the Very Large Telescope facility disprove the assumption that the supermassive black hole at the centre of the Milky Way devours nearby dust objects.
An international research team led by PD Dr Florian Peißker at the University of Cologne has used the new observation instrument ERIS (Enhanced Resolution Imager and Spectrograph) at the Very Large Telescope (VLT) facility in Chile to show that several so-called ‘dusty objects’ follow stable orbits around the supermassive black hole Sagittarius A* at the centre of our galaxy. Earlier studies had surmised that some of these objects could be swallowed up by the black hole. New data refute this assumption. The findings have been published under the title ‘Closing the gap: Follow-up observations of peculiar dusty objects close to Sgr A* using ERIS’ in the journal Astronomy & Astrophysics.
The study focused on four of these unusual celestial bodies, which have been the subject of much discussion in recent years. In particular, G2 was long regarded as a pure dust and gas cloud. It was thought to have been initially elongated by the gravitational pull of Sagittarius A*, a process known as ‘spaghettification’, before being destroyed. However, the specific observations made with ERIS, which captures radiation in the near-infrared range, show that G2 follows a stable orbit. This is an indication that there is a star inside the dust cloud. These results confirm that the centre of the Milky Way is not only destructive, but can also be surprisingly stable.
The binary star system D9, which Peißker and his team discovered in 2024, also remains stable despite the enormous tidal forces of the black hole. It is the first known binary star system to be observed so close to a supermassive black hole. In theory, the stars involved in D9 could merge to form a single, more massive star due to strong tidal forces. However, the ERIS data so far show that D9 remains intact. The same applies to Objects X3 and X7, which also orbit in stable orbits and are therefore less fragile than earlier models had suggested.
“The fact that these objects move in such a stable manner so close to a black hole is fascinating,” says Florian Peißker. “Our results show that Sagittarius A* is less destructive than was previously thought. This makes the centre of our galaxy an ideal laboratory for studying the interactions between black holes and stars.”
The results demonstrate that the processes at the centre of the Milky Way are more complex than previously assumed. “The supermassive black hole at the centre of the Milky Way has not only the capability to destroy stars but it can also stimulate their formation or the formation of pretty exotic dusty objects, most likely via mergers of stellar binaries,” says Michal Zajaček from Masaryk University in Brno (Czech Republic). Future observations from the ERIS and the Extremely Large Telescope (ELT) – which is currently under construction – should help to further track the evolution of these objects and to understand how stars can survive even in the extreme regions of the universe.
Media Contact: PD Dr Florian Peißker Institute of Astrophysics +49 221 470 7791 peissker@ph1.uni-koeln.de
In our latest SILCC paper, we perform magneto-hydrodynamic simulations to investigate the impact of metallicity on the interstellar medium (ISM). In fact, gas-phase metallicity affects heating and cooling processes in the star-forming ISM as well as ionising luminosities, wind strengths, and lifetimes of massive stars. Our simulations include non-equilibrium chemistry, a space- and time-variable far-UV background and cosmic ray ionisation rate, metal-dependent stellar tracks, the formation of HII regions, stellar winds, type II supernovae, and cosmic ray injection and transport. The simulations assume a gas surface density of 10 M_sun pc−2 and span metallicities from 1/50 Z_sun to 1 Zsun. Among our results, we find that for decreasing metallicity, the star formation rate decreases by more than a factor of ten, the mass fraction of cold gas decreases from 60% to 2.3%, while the volume filling fraction of the warm gas increases from 20% to 80%. In particular, we analyze the conditions in which our stars form, computing the ratio of the H2 mass to the H mass in star-forming regions, and we find that this ratio depends on the metallicity. In fact, we find that at solar metallicity (upper panel), massive stars form in an almost fully molecular gas, whereas at extremely low metallicity (bottom panel), they form in almost fully atomic gas. Including the major processes that regulate ISM properties, this study highlights the strong impact of gas phase metallicity on the star-forming ISM.
XMAS after work events have been organized by the Student Council!
The first event will be in Bonn, on the 3rd of December at 18:00. CRC students meet at the foyer in the Max Planck Institute for Radioastronomy and then go to the market. The second event will be in Cologne on the 10th of December, and the students meet at the door of the I Physics Institute at 18:00.
Gastvortrag: Kants Kosmologie aus Sicht der modernen Astrophysik
Immanuel Kant (1724 – 1804) stellte Spekulationen über den Aufbau unseres Milchstraßensystems an und favorisierte die Hypothese einer außergalaktischen Stellung der beobachteten „Nebelflecken“ am Himmel. Dennoch betrachtete er die Kosmologie skeptisch weil entsprechend seiner Erkenntnistheorie die Welt als Ganzes kein Gegenstand der Erfahrung sein kann. Im 20. Jahrhundert haben Beobachtungen und die theoretische Astrophysik seine Vorbehalte gegenüber einer physikalischen Kosmologie revidiert.
Referent: Prof. Dr. Hans-Joachim Blome (Fachhochschule Aachen)
Gastvortrag: Der “Urknall” – Geburt des Weltalls aus dem Nichts?
Eine der erstaunlichsten Entdeckungen der Astronomie ist die allgemeine Ausdehnung des Weltalls. Zur Beschreibung der Entwicklung des Kosmos wurde das “Standardmodell” entwickelt, das jedoch zwei geheimnisvolle Kräfte benötigt: die “Dunkle Materie” und die “Dunkle Energie”. Wie glaubhaft ist dieses Modell? Ist unser Verständnis der Gravitation unzureichend? Ist das Universum älter als bisher angenommen, wie neue Beobachtungen des James Webb Weltraumteleskops andeuten? Sogar der “Urknall”, Beginn von Raum und Zeit, gerät ins Zwielicht. Entstand unser Weltall etwa durch den Kollaps eines früheren Universums? Oder ist unsere Welt gar nur ein kleiner Teil eines viel größeren “Multiversums”?
The next SFB-colloquium will be on December 2 at 2 pm in the seminar room 0.02 of the Max Planck Institute for Radio Astronomy in Bonn and will start with a coffee reception at 1:45 pm in front of the room. The colloquium will also be streamed via Zoom.
Michael Kramer from the Max Planck Institute for Radio Astronomy will talk about “Geometry, geometry, geometry …“.
Abstract: As with many physical systems, geometry plays a crucial role, if not the crucial role, in the study of pulsars. Its importance cannot be overestimated. It determines how and if we see these objects, plays a role in their formation during the death of massive stars and in their possible disappearance from view. Geometry determines whether they are merely radio sources or whether they can be seen as gamma-ray pulsars. Geometry is also important for testing gravity and understanding the neutron star population. Often, it is not even constant. This talk will demonstrate why geometry is important, how we determine it and present new results and old puzzles
Please join us for the second event of Season 8 of Astronomy on Tap Bonn! It will take place at The Fiddlers Pub (Frongasse 9, Endenich) on Tuesday, 25 at 19:00 featuring talks on
“Der Stern S2 und das dunkle Geheimnis im Zentrum der Milchstraße” by Dr. Gunther Witzel (DE)
“Compiling the Cosmos: The Journey of Astronomers and Algorithms” by Tejas Oak (EN)
There is the opportunity to win wonderful prizes, so do not miss out! We recommend you reserve a table in advance though.
Every month, Astronomy on Tap Köln brings you fun and enlightening talks in German and English! Join us to find what Astrophysicists are up to in solving the puzzles of the cosmos.
Make sure to show off your smarts in the exciting Pub Quiz. Winners get astronomy goodies from the European Southern Observatory, SOFIA and other cool telescopes, to take home!
Check-in now for free! or simply respond to this email with the no. of people you plan to bring to the event (not mandatory but helps us to make adequate arrangements)
Program 04.Dec 2025
“Diamantring im all” (auf Deutsch) by Simon Dannhauer
Das meiste, was man zu Thema wissen müssen, hat Rihanna bereits in ihrem Song „Diamonds“ mit der Zeile „Shine bright like a diamond … a diamond in the sky“ auf den Punkt gebracht. Nur dass eine solche Behauptung in der Wissenschaft eben Vorschläge, Diskussionen, Teleskope und vieles mehr erfordert. All diese Dinge, die hinter der endgültigen Veröffentlichung verborgen sind, stehen im Mittelpunkt dieses Vortrags.
” Telescopes: Their Origins and the Universe They Revealed ” (in English) by Flavia Carolina Santos Do Amaral A journey through the origins of telescopes: how simple lenses sparked a scientific revolution and opened humanity’s first window to the universe.
The structure of gas and dust resembles a glowing diamond ring. Computer simulations and observations made on board the ‘flying observatory’ SOFIA are now able to explain the special shape .
An international team led by researchers from the University of Cologne has solved the mystery of an extraordinary phenomenon known as the ‘Diamond Ring’ in the star-forming region Cygnus X, a huge, ring-shaped structure made of gas and dust that resembles a glowing diamond ring. In similar structures, the formations are not flat but spherical in shape. How this special shape came about was previously unknown. The results have been published under the title ‘The Diamond Ring in Cygnus X: an advanced stage of an expanding bubble of ionized carbon’ in the journal Astronomy & Astrophysics.
The ring has a diameter of around 20 light years and shines strongly in infrared light. It is the relic of a former cosmic bubble that was once formed by the radiation and winds of a massive star. In contrast to other similar objects, the ‘Diamond Ring’ does not have a rapidly expanding spherical shell, but only a slowly expanding ring.
“For the first time, we observed the final stage of such a gas bubble in a distinctly flat cloud structure,” explains Simon Dannhauer from the University of Cologne’s Institute for Astrophysics, who lead the study. “The bubble has ‘burst’, because gases were able to escape into the thinner areas around it. All that remained was the particular flat shape.”
Computer simulations show that the bubble initially expanded in all directions and later escaped perpendicular to the cloud. What remained was the structure of the ‘Diamond Ring’ that is visible today. This cosmic formation is estimated to be around 400,000 years old – very young compared to the lifespan of massive stars. Sebastian Vider from the University of Cologne carried out these computer simulations on the new ‘RAMSES’ supercomputer.
The bubble consisting of ionized carbon was once inflated by a hot star with a mass approximately 16 times that of our Sun. This star heats up the gas and dust until it glows. Observations like this are technically very demanding and were only possible with the help of the flying observatory SOFIA (Stratospheric Observatory for Infrared Astronomy). With SOFIA, a modified Boeing aircraft that flies at an altitude of 13 kilometres or more, researchers can observe a wavelength range of light that is not accessible from Earth. In doing so, the researchers were able to precisely measure the movement of the gas: The ring expands at around 1.3 kilometres per second – this corresponds to around 4,700 km/h and is actually quite slow compared to similar bubbles.
The discovery provides valuable insights into how the radiation and winds of young stars shape their environment and therefore also influence the formation of new stars. “The ‘Diamond Ring’ is a prime example of how enormous the influence of individual stars can be on entire cloud complexes,” says Dr Nicola Schneider, co-author of the study. “Such processes are crucial for understanding the formation of stars in our Milky Way,” continues Dr Robert Simon.
Yet there’s still one small disappointment for the romantics. The study also shows that what looks like a ‘Diamond Ring’ from Earth actually consists of two individual objects. It seems as if the ‘Diamond’, a cluster of young stars, is merely part of the ring. In fact, it is located a few hundred light years in front of it.
Media Contact: Simon M. Dannhauer Institute for Astrophysics +49 221 470 8353 dannhauer@ph1.uni-koeln.de
SFB1601 members visited the DLR Cologne, kindly invited by Alexander Rüttgers and Achim Basermann.
After learning about the history of Astronautics we started our visit in the European Astronaut Center (EAC) with highly interesting information about ESA astronaut training, how to survive in space and how the ISS was built while watching live pictures from space. Actual experiments on the effects of space and the lack of gravity on the human body as well as radiation were the main topics in the Institute of Aerospace Medicine.
After the Space Control Center (what time is it on the ISS?) and lunch in the cafeteria, two exciting presentations showcased the DLR’s research in the fields of quantum computing and mapping of space debris: Dr. David DA COSTA: “Collective neutrino oscillations in a quantum computer” Patrick Lenz: “BACARDI – A catalogue for space debris”.
Infrared- or submillimeter-bright dusty star-forming galaxies (DSFGs) are key contributors to the cosmic star formation rate density in the early universe, preserving the imprint of its star formation history [1-2]. We are at the forefront of observations, having secured spectroscopic redshifts for about 400 DSFGs up to redshift z ~ 7. Among these, the NOEMA z-GAL is the largest sample of 135 meaningfully selected high-z DSFGs (S500µm > 80 mJy) from the Herschel fields, whose spectroscopic redshifts are robustly measured mainly using higher-J CO lines [3].
In our recent work focused on Vz-GAL, a large program using NSF’s Very Large Array (VLA), we have focused on investigating galaxy evolution by characterizing the cold gas, fuel for star formation, in 106/135 z-GAL galaxies spanning from the epoch of reionization (redshift z ~ 6, approximately 1 Gyr after the Big Bang) to the post-cosmic noon era (z ~ 1, roughly halfway through the universe’s current age). Vz-GAL targets faint CO(1-0) transition in these high-z galaxies, which is essential for accurately probing cold molecular gas and constraining gas excitation conditions, despite the observational challenges involved. Using Vz-GAL, we double the currently available CO(1-0) measurements at high-zand robustly calibrate gas masses for this homogeneously selected, flux-limited, large statistical sample.
Our analysis compares integrated CO(1-0) line luminosities (as a gas mass proxy) with total infrared luminosities (as an SFR proxy, [4-5]) to explore the Kennicutt-Schmidt correlation and redshift evolution of gas depletion timescales, revealing a galaxy’s evolutionary state. Here we compare our high-z DSFGs to local galaxy populations to understand their physical environments. In addition, rigorously derived CO excitation line ratios yield new insights into the physical state of molecular gas in the early universe. Our preliminary findings regarding gas-to-dust mass ratios and [CI]/CO luminosity ratios further emphasize the necessity for refined radiative transfer modeling fewer ad-hoc assumptions, which can characterize the star-forming interstellar medium via simultaneously fitting the spectral energy distribution of dust and CO line. We find consistent [CI](1-0)/CO(1-0) ratios across redshifts, suggesting the use of [CI](1-0) as an alternative cold gas tracer at z > 1.
Join us for Astronomy on Tap Bonn’s Halloween edition! You can attend exciting astronomy talks in English and German at Fiddlers Pub (Frongasse 9, Endenich) on Tuesday 28 at 19:00.
– “Who’s hiding behind the Gamma-ray glow?” by Lucía Gebauer (myself) (EN) – “Was raubt Kosmologen den Schlaf?” by Lucas Porth (DE)
Since it’s a spooky-themed event, feel welcome to come in costume. There is the opportunity to win wonderful prizes, so do not miss out!
Every month, Astronomy on Tap Köln brings you fun and enlightening talks in German and English! Join us to find what Astrophysicists are up to in solving the puzzles of the cosmos.
Make sure to show off your smarts in the exciting Pub Quiz. Winners get astronomy goodies from the European Southern Observatory, SOFIA and other cool telescopes, to take home!
Check-in now for free! or simply respond to this email with the no. of people you plan to bring to the event (not mandatory but helps us to make adequate arrangements)
Program 30.Oct 2025
“Untote Galaxien” (auf Deutsch) by Nikolaus Sulzenauer
Aus Lehrbüchern kennen wir Bilder von nahezu perfekten, hoch-symmetrischen Spiralgalaxien – die wie in Neonfarben leuchten. Aber wie sind diese Galaxien eigentlich zu ihrer Hochglanzform gekommen? Und was lässt sich über die Entstehung ihrer Schwestergalaxien, den leuchtkräftigen, annähernd makellosen elliptischen Galaxien, sagen? Die Forschung zeigt, dass das heutige Erscheinugsbild dieser galaktischen Monumente einem stetigen Wandel unterworfen ist. Die beeindruckende Erscheinung dieser Galaxien bedingt eine gewaltsame Kette an Ereignissen, die uns zurückführt in die Frühzeiten des Kosmos. In dieser Präsentation werde ich Licht in die Katakomben der Entwicklung von massereichen Galaxien werfen, und von deren spukhaften Auferstehung als untote Galaxien im frühen Universum berichten.
“Wrath of the Wolf-Rayets ” (in English) by Prachi Prajapati
This talk will take you on a thrilling voyage into the haunting final stages of massive stars—Wolf-Rayets. Everything in the grand design of Universe has a purpose—and so do these monsters, shrouded in cosmic mystery and rage. Let us discover how these ghosts of dying stars may be hurling cosmic rays our way!
Hat die NASA den ersten Hinweis auf außerirdisches Leben erschnüffelt? Das James-Webb-Weltraumteleskop (JWST) hat in der Atmosphäre des Exoplaneten K2-18 b Methan und CO₂ nachgewiesen – und möglicherweise auch Dimethylsulfid, ein Gas, das auf der Erde ausschließlich durch biologische Prozesse entsteht. Doch wie verlässlich ist ein Signal mit einer Signifikanz von „drei Sigma“? Der Vortrag bietet einen Einblick in die Methoden zur Entschlüsselung von Exoplanetenatmosphären und zeigt, wie die Wissenschaft zwischen fundierten Ergebnissen und bloßer Spekulation unterscheidet.
The CRC 1601 Sustainability Board invites you to the next Sustainability Day. A full afternoon is dedicated to interesting topics and workshops and will be completed by a vegan BBQ accompanied by a quiz.
Registration is closed, please contact a member of the sustainability board if you would like to join.
In our recent Astronomy & Astrophysics paper, we explore the prospects of using [CII] line intensity mapping (LIM) observational technique with the upcoming FYST / Prime-Cam instrument to study galaxies that formed about 0.5–1.5 billion years after the Big Bang. LIM measures the cumulative emission from many faint galaxies without resolving them individually, offering a powerful way to trace the contribution of sources too faint to be detected even with state-of-the-art telescopes. The [CII] 158 µm line is a key tracer of star formation in these early systems, but its signal is strongly contaminated by foreground CO emission from later galaxies along the line of sight.
To address this challenge, we generate mock [CII] and CO maps by post-processing the IllustrisTNG300 simulation and test a masking strategy in which bright CO emitters are identified from an external galaxy survey catalog and removed. Our results show that, without masking, CO dominates the signal at almost all observing frequencies, with the exception of the higher end of the frequency range of our telescope. After masking, the [CII] signal becomes accessible across most frequencies. At the highest frequencies, however, which probe the earliest and most distant galaxies, the CO contamination remains severe. In this regime, masking alone is not sufficient, highlighting the need for complementary techniques such as line-deconfusion or cross-correlations with other tracers.
This study demonstrates that, with the support of ancillary galaxy surveys, the [CII] LIM signal from early galaxies can be detected, a first step toward applying LIM to trace star formation within the first generations of galaxies.
The Public Observatory Cologne is a private institution which is run by the members of the “Vereinigung der Sternfreunde Köln e.V.” on a voluntary basis. This association of interested amateurs and amateur astronomers was founded in 1922 with the aim of disseminating basic astronomical knowledge to the public and promoting the training and further education of active amateur astronomers within the scope of the available possibilities.With the 60cm refractor “Cologne Large Telescope” (CLT) installed in 2012, the Volkssternwarte Köln operates the largest freely accessible telescope in North Rhine-Westphalia
Wissenschaftliche Durchbrüche entstehen selten linear – der Weg von der ersten Hypothese zur Publikation ist geprägt von Umwegen, Zufällen und unerwarteten Entdeckungen. Dieser Prozess versteckt sich meist hinter der finalen Publikation und bleibt der Allgemeinheit im Dunklen. Dieser Vortrag beleuchtet den oft verborgenen Forschungsprozess am Beispiel aktueller Forschung zur Sternentstehung in unserer Milchstraße. Wie beeinflussen Sterne die Molekülwolken, aus welchen sie entstehen? Was bedeutet das für die nächste Generation von Sternen? Die Suche nach fundamentalen Antworten auf diese Fragen ist oft überraschend menschlich und macht Forschung greifbar. Dabei zeigt sich oft auch, warum neue Fragen häufig neue Instrumente erfordern, wie das revolutionäre FYST-Teleskop, welches momentan in Chile gebaut wird.
An Einstein cross is a phenomenon where a distant object appears as multiple images arranged in a cross-like pattern around a foreground galaxy. A fifth image in the newly discovered cross reveals the presence of dark matter.
An international team of astronomers has observed a galaxy in the early universe that has the rare shape of an Einstein cross. The Einstein cross is an astronomical phenomenon in which the light of a very distant galaxy is bent by the gravitational force of an intervening galaxy in front of it. This makes the distant object appear to us as if it were several, usually four, images arranged in a cross shape around the galaxy in front of it – an effect known as gravitational lensing. The Einstein cross that has now been discovered also has a fifth central image. The researchers showed that the arrangement of these five images can only be explained by the presence of a dark matter halo associated with the foreground group of galaxies. The results have been published under the title ‘HerS-3: An Exceptional Einstein Cross Reveals a Massive Dark Matter Halo’ in The Astrophysical Journal.
The researchers used observations from the Northern Extended Millimetre Array (NOEMA, Institut de Radioastronomie Millimétrique – IRAM, France), the Atacama Large Millimeter/submillimeter Array (ALMA, Chile), the Karl G. Jansky Very Large Array (VLA, USA) and the Hubble Space Telescope (HST, NASA/ESA). The discovery offers new insights into dark matter and the early universe.
So-called gravitational lensing effects such as the Einstein cross occur when the gravity of a very massive galaxy (or group of galaxies) bends the light from even more distant objects. To us, these distant objects appear distorted, multiplied or stretched into arcs and rings in the sky. This results in an optical magnification of the objects, enabling an in-depth analysis of galaxies in the early universe.
Objects such as the Einstein Cross are also used to determine the properties of dark matter in galaxies and star groups and clusters. Current theories suggest that dark matter, which accounts for approximately 80 per cent of the mass of the universe, consists of particles that have yet to be identified and do not interact with visible light. Although dark matter is invisible, its existence can be inferred from its gravitational effects.
In this study, the images from NOEMA showed the galaxy HerS-3, which is 11.6 billion light years away, multiplied into five images and forming a nearly perfect cross. An Einstein cross is a rare phenomenon, but this one is particularly unusual due to the bright, central fifth image. The five images of HerS-3 all show the same molecular emission lines, indicating that they are multiple images of the same galaxy.
The observations through the ALMA telescope revealed the detailed structures of the individual images. The NOEMA and ALMA data are complemented by data from the Very Large Array tracing the radio waves and the cold molecular gas. The latter data were analysed by Prachi Prajapati, doctoral candidate in the research group of Professor Dr Dominik Riechers at the University of Cologne’s Institute for Astrophysics, and show the five images of the galaxy in cold molecular gas, which is essential for star formation. This is the first time that an Einstein cross is detected at submillimetre and radio wavelengths.
The light from HerS-3 is bent by four massive foreground galaxies. These form the core of a larger group of at least ten other galaxies that are 7.8 billion light years away from Earth and were identified in the near-infrared with the Hubble Space Telescope. In order to determine the properties of the distant galaxy HerS-3 and to explore the galaxy group in the foreground, the researchers simulated how gravity bends the light of galaxies. It turned out that the exact arrangement of the five images of the Einstein cross cannot be reproduced in the simulation if only the four visible massive galaxies located near HerS-3 and located at the centre of the galaxy group are taken into account.
The fact that there is no other visible galaxy at the same distance close to the foreground galaxy group therefore indicates the existence of a large, invisible component: a concentration of dark matter associated with the galaxy group. Only by adding this massive component, which lies at the centre of mass of the group, does the reconstruction exactly match the properties of the five images. The estimated mass of the dark matter halo amounts to several trillion solar masses.
The HerS-3 system with its fifth central image in the form of the Einstein cross makes it possible to observe the complex structure of a galaxy during the most active phase of the universe’s development. Studying such systems could help to uncover the properties of dark matter and understand how it influenced the earliest stages of cosmic evolution.
In addition to researchers from the University of Cologne, scientists from the Institut d’Astrophysique de Paris of the Sorbonne Université in Paris and the Institut de Radioastronomie Millimétrique (Institute for Radio Astronomy in the Millimetre Range, IRAM) also contributed to the publication.
Picture: Nicolás Lira Turpaud (ALMA-Observatorium) & Pierre Cox (adjusted by Cox et al. 2025)
Media Contact: Professor Dr Dominik A. Riechers Institute for Astrophysics +49 221 470 76027 riechersph1.uni-koeln.de
Every month, Astronomy on Tap Köln brings you fun and enlightening talks in German and English! Join us to find what Astrophysicists are up to in solving the puzzles of the cosmos.
Make sure to show off your smarts in the exciting Pub Quiz. Winners get astronomy goodies from the European Southern Observatory, SOFIA and other cool telescopes, to take home!
Check-in now for free! or simply respond to this email with the no. of people you plan to bring to the event (not mandatory but helps us to make adequate arrangements)
Program 18.Sept 2025
“Von der Rotation zur Detektion – Der Rotations-Fingerabdruck von Molekülen” (auf Deutsch) by Dr. Luis Bonah
Der Talk handelt vom Rotations-Fingerabdruck von Molekülen, wieso er für die Detektion von Molekülen im Weltall essentiell ist, und wie wir ihn im Labor rekonstruieren können.
“Life beyond Earth” (in English) by Damian Perergina Garcia
In my pressentation I will explore about the many different forms of life that have been ignored/neglegted by astrophysicists in order to search for extratraterrestrial lifeforms, among them extremofiles here on earth that would find Mars atmosphere warm and cozy.
Warum sind Sterngeburten rar und welche Prozesse bremsen die Sternentstehung? Einfache Überlegungen führen zu deutlich überhöhten Geburtenraten von Sternen. Es müssen also weitere Mechanismen existieren, die die Geburtenrate verringern. Wir gehen auf die Suche dieser Mechanismen und widmen uns danach der Milchstraße und der M33 Galaxie, um zu untersuchen, wie sich die Stern-Geburtenraten in beiden Galaxien unterscheiden.
In our recent A&A paper (Dannhauer et al., subm.), we investigated the “Diamond Ring” in Cygnus X, a striking 6 pc wide ring-like structure seen in [C II] 158 μm and dust emission. Unlike the three-dimensional [C II] shells discovered in recent years, the Diamond Ring reveals itself as the first pure ring, slowly expanding at only ~1.3 km/s.
The [C II] data stem from velocity-resolved SOFIA/upGREAT maps from the FEEDBACK legacy program. Combined with archival molecular line data, dust continuum, radio observations, and new spectroscopy of the central star, we establish a picture of the nature of this object. The ring is powered by a B0.5e star located near its center which also creates an HII region in the ring cavity. Interestingly, the bright “Diamond” to the southeast of the ring is not part of the same structure, but an unrelated clump of dense gas and young stars at a completely different velocity along the line of sight.
We carried out dedicated 3D simulations of stellar feedback in a flat molecular slab, in order to follow the evolution of a ring-like structure. These simulations demonstrate that the Diamond Ring represents the terminal phase of a [C II] bubble evolving inside such a slab. In its early life, the bubble expanded in three dimensions. However, gas moving perpendicular to the plane of the slab quickly dispersed into the surrounding lower-density medium dropping below our detection limit, while the parts confined to the slab persisted as a coherent, slowly expanding ring.
From the observations and simulations, we derive an age of only ~400–500 kyr, much younger than classical estimates assuming spherical expansion, with cloud dispersal taking over after 100 kyr as also suggested by previous studies. The Diamond Ring highlights how the geometry of molecular clouds, especially flat clouds which might be common, fundamentally shapes stellar feedback.
On Tuesday, August 26, 08:00 pm, Markus Röllig, a former member of the I. Physikalisches Institut and managing director of “Physikalischer Verein Frankfurt”, will present this years evening talk, which will guide us and the interested public into the fascinating world of building astronomical instrumentation and its use for astrophysical research. His talk is entitled:
Revealing the cosmos with the James Webb Space Telescope!
26.08.2025 8:00 pm Hörsaal I (Lecture Hall I) I Physics Institute University of Cologne
Priv.-Doz. Dr. Markus Röllig Physikalischer Verein Frankfurt
NASA’s James Webb Space Telescope heralds the next era of infrared astronomy. With spectacular new results, astronomers are gaining unprecedented insight into the secrets of our universe. The telescope, the instruments on board, and the details of its mission are more complex than any previous mission. We take a closer look at the technical aspects of the mission and its latest astronomical results, including the spectroscopic detection of dimethyl sulfide, a molecule produced on Earth, particularly by marine microorganisms. How close are we really to discovering extraterrestrial life?
The telescope FYST, which is currently being re-assembled on 5600 above sea level the top of Cerro Chajnantor in the Chilean Atacama Desert, was assembled from lego bricks by Yoko Okada. The instructions are ready for download and we welcome replicas and expansions.
The process that brings galaxies to reduce and definitely halt to form stars (the star formation quenching) is the result of a complex interplay of phenomena that are difficult to disentangle without an adequate and statistically significant sample of galaxies. Given this, we have assembled the integrated Extragalactic Database for Galaxy Evolution (iEDGE), collecting stellar continuum, nebular emission lines, and molecular gas information for hundreds of galaxies in the local Universe. iEDGE is, to date, the most comprehensive and extensive database of (CO-based) integrated galaxy properties.
The first iEDGE paper (Colombo et al. 2025a, arXiv:2507.06375) introduces the homogenised database of 643 nearby CALIFA galaxies combining optical integral field unit (IFU) and CO measurements, revealing a strong bimodality between passive early-types and star-forming spirals, with centrally suppressed star formation efficiency (SFE) in passive systems nearly two orders of magnitude below typical global values.
Building on this, the second study (Colombo et al. 2025b, arXiv:2507.06406) examines how star formation scaling relations evolve along galaxies at different quenching stages, showing that molecular gas mass and gas fractions decline steadily from star-forming to retired galaxies, while SFE remains roughly constant during the transition before dropping sharply—particularly in galaxy centres—consistent with inside-out quenching.
Finally, the third paper (Bazzi et al. 2025, arXiv:2507.06709) explores the role of AGN activity in this process, finding that AGN hosts exhibit higher molecular gas masses at fixed quenching stage but follow similar SFE and gas fraction trends as non-active galaxies, suggesting no prominent instantaneous effects of AGN feedback on global star formation properties.
iEDGE will help to contextualise dedicated resolved studies of ageing galaxies, aiming to image the objects in which stars are actually born, the Giant Molecular Clouds, and understand whether their properties and dynamical states can explain why galaxies reduce their star formation efficiency in particular regions. Additionally, the database will be used to assess whether the quenching can be explained by a break in the transition from atomic to molecular to dense gas, by including information from the 21 cm line and dense gas tracers such as high-J CO and HCN transition lines.
Authors: Dario Colombo, Zein Bazzi, Frank Bigiel (AIfA, University of Bonn)
Figure: A collection of 200 CO spectra (roughly a third of the full amount included in the database) overplotted on the SDSS images of the galaxies. The panels are ordered by the logarithmic distance from the star formation main sequence (ΔSFMS), and they are colour-encoded considering the amount of molecular gas inferred from the CO detections. The randomness of the colour distribution suggests that an advanced stage of quenching is not necessarily implied by the absence of molecular gas. The iEDGE is available for download on Zenodo: https://zenodo.org/records/15822433. Image credits: D. Colombo, V. Kalinova, Z. Bazzi & the EDGE-CALIFA collaboration.
In recent years, the fine-structure line of C+ at 158 microns – the [CII] line – has gained significant attention as a molecular gas tracer, particularly at z ≳ 4. Being one of the brightest emission lines in galaxies, it offers a unique window into the molecular ISM of distant galaxies, where conventional tracers like CO become observationally expensive.
We have tested the reliability of this line as a tracer of the molecular gas mass (Mmol) using a statistical sample of galaxies at different cosmic epochs from high-resolution cosmological simulations – the Marigold simulations. Our analysis reveals that the [CII]- Mmol correlation is relatively weak at z ≳ 5, but becomes progressively stronger over time. We also identify a clear secondary dependence on the star formation rate (SFR), accounting for which, significantly improves Mₘₒₗ predictions by a factor of 2.3 at all redshifts.
We have further examined the time evolution of the [CII] luminosity function and the cosmic [CII] luminosity density (ρ[CII]) and found that faint (L[CII] < 107 L⊙) galaxies contribute nearly half of the cosmic ρ[CII] at z ≳ 7. Since these faint galaxies fall below the sensitivity limits of current instruments, detecting them would require alternative observational strategies.
Figure caption: a) Figure showing the redshift-evolution of the [CII]-Mmol relation in galaxies from the Marigoldsimulations. The purple bins show the distribution of simulated galaxies and the red line gives the ordinary least squares linear fit to these galaxies. The blue, lime, and orange lines show previous empirical and numerical estimates for specific redshifts. We note that the [CII]-Mmol correlation tightens and strengthens over time, as indicated by the decreasing scatter (σ)and increasing Spearman’s rank correlation coefficient (ρ) towards lower redshifts.
b) Figure showing the redshift-evolution of the simulated [CII] luminosity function (LF) and a comparison with observational estimates (in black). The coloured lines represent the best-fit double power-law to the simulated LF and the shaded area represents the central 68% credibility range obtained using MCMC chains.
Beobachten, staunen, erleben – das Universum entdecken mit der bundesweiten Langen Nacht der Astronomie! In der Langen Nacht der Astronomie laden die Stiftung Planetarium Berlin, die Gesellschaft Deutschsprachiger Planetarien und die Vereinigung der Sternfreunde gemeinsam mit zahlreichen astronomischen Einrichtungen deutschlandweit dazu ein, mit einem abwechslungsreichen Programm die Begeisterung für die Astronomie zu teilen.
In cooperation with the Public Observatory Cologne an exciting program for the Long Night of Astronomy was held in September.
20:00 Uhr Lecture: FYST – The new Fred Young Submillimeter Telescope
At an altitude of 5,600 meters on the Cerro Chajnantor mountain in the Chilean Atacama Desert, one of the most modern radio teleascopes in the world is being built in the design of a giant webcam the size of a house. Measuring 6 meters across, the FYST will provide insights into the birth of the first stars after the Big Bang and the formation of stars and galaxies. Speaker: Prof. Dr. Dominik Riechers (University of Cologne)
20:00 o’clock: Visit of the Observatory
In clear weather, observation of the ringed planet Saturn and objects in our Milky Way with the telescopes of the observatory on the terrace.
21:00 o`clock: Visit of the Observatory and planetarium presentations
In cloudy weather, a tour of the observatory with the 60cm Cologne large telescope alternating with a planetarium presentation about the objects in the Cologne sky on 13.09.2025. (An event for the whole family including children aged 10 and over.)
Additionally, a lego model of the FYST telescope will be presented and visitors will have the opportunity to observe the sky through several small telescopes on the roof terrace of the observatory.
20:30-21:00: Amateurastronomie und Bürgerwissenschaft / Citizen Science
20:39 Uhr: „Astronomisches ABC: Teleskope“ und Astronomische Aufnahmen der Sternfreunde Berlin e.V.
20:44 Uhr: „Citizen Science“; Unistellar
21:00-21:30: Podiumsdiskussion live aus Berlin mit Vertretern des Deutschen Zentrums für Luft- und Raumfahrt, des Deutschen Zentrums für Astrophysik und des Leibniz-Instituts für Astrophysik, moderiert von Tim Florian Horn
21:30-22:30: »Astronomisches ABC« und Vortrag »Von Sternen und Märkten«
21:43 Uhr: „Astronomisches ABC, Asteroiden“, „Astronomisches ABC, Umlaufbahn“, „Astronomisches ABC, Cepheiden“; Asteroiden und Cepheiden: Dr. Carolin Liefke, Haus der Astronomie, Heidelberg; Umlaufbahnen: Alexander Putz, Sternfreunde Berlin
21:52 Uhr: „Sterne und Märkte“; Udo Siepmann, Walter-Hohmann-Sternwarte Essen
22:13 Uhr: Astronomische Aufnahmen der Sternfreunde Berlin
22:16 Uhr: „Astronomisches ABC: XXM-Newton“, „Astronomisches ABC: Zwerggalaxien“; XXM: Dr. Iris Traulsen, Leibniz-Institut für Astrophysik Potsdam; Zwerggalaxien: Dr. Marcel Pawlowski, Leibniz-Institut für Astrophysik Potsdam
You can attend exciting astronomy talks in English and German at Fiddlers Pub (Frongasse 9, Endenich) on Tuesday 24 at 19:00.
– “The Mystery of the Doppelgänger Galaxies” by Dr Veselina Kalinova (EN) – “Deep Learning im Deep Sky – von Schulbussen, autonomen Fahrzeugen und KI im Zeitalter großflächiger Himmelsdurchmusterungen” by Jakob Dietl (DE)
There is the opportunity to win wonderful prizes, so do not miss out!
In der chilenischen Atacama-Wüste stehen die leistungsstärksten Teleskope der Welt, und ständig kommen neue hinzu. Etwa das Extremely Large Telescope (ELT) der Europäischen Südsternwarte (ESO). Es soll 2028 fertiggestellt und das weltweit größte optische Teleskop werden. Oder das Fred Young Submillimeter Telescope (FYST). Es wurde in Deutschland gebaut und Ende März an seinen Aufstellungsort im Norden Chiles transportiert. Auf mehr als 5.600 Metern soll es zusammen mit dem University of Tokyo Atacama Observatory (TAO) das höchstgelegene Teleskop der Erde werden.
Warum werden ständig neue Teleskope gebaut?
Unterschiedliche Teleskope beobachten unterschiedliche Dinge, das heißt, Strahlungen unterschiedlicher Wellenlängen entlang des elektromagnetischen Spektrums. Es gibt zum Beispiel Teleskope, die sehr große Radiowellen empfangen, Teleskope, die auf sichtbares Licht ausgelegt sind, und Teleskope, die Infrarot- oder Terahertzstrahlung untersuchen. Das ist Strahlung im sogenannten Submillimeter-Wellenlängenbereich, zwischen 3,1 und 0,2 Millimeter.
Zu dieser Art Teleskop zählt auch das FYST. „Die Gase und der Staub, in dem Sterne entstehen, das sogenannte interstellare Medium, können wir im visuellen Bereich nicht beobachten“, erklärt Dominik Riechers, Astrophysiker an der Uni Köln. Aber: „In längeren Wellenlängen strahlen diese plötzlich extrem hell.“ Das FYST ist dabei das erste Teleskop, dass Terahertzstrahlung im gesamten südlichen Himmel wird beobachten können, da es wie ein Weitwinkelobjektiv funktioniert. Es ist ein gutes Beispiel dafür, warum es immer wieder neue Teleskope gibt: verbesserte Technik, andere Wellenlängenbereiche oder unterschiedliche Bereiche des Himmels, die beobachtet werden.
Warum stehen so viele Teleskope in der chilenischen Atacama-Wüste?
„Chile ist einfach der beste Standort der Welt für Teleskope“, sagt der chilenische Astrophysiker Pablo Garcia Fuentes. Im Terahertz- und Infrarotbereich spielt vor allem die Luftfeuchtigkeit eine wichtige Rolle. Die Wassermoleküle in der Atmosphäre absorbieren die Strahlung. Da die Durchlässigkeit der Atmosphäre mit der Höhe zunimmt, gilt: je höher und trockener der Standort, desto besser für die Submillimeter-Astronomie.
Im optischen Bereich wird die Strahlung nicht so stark absorbiert, aber Turbulenzen in der Luft führen zu Verzerrungen, die korrigiert werden müssen, damit die Sterne nicht flackern. Dafür genügt es, wenn das Teleskop in 2.000 bis 3.000 Metern Höhe steht. Radioteleskope wiederum brauchen einen Standort, der möglichst weit weg von menschengemachter Störstrahlung ist. Die Atacama-Wüste als besonders trockene, vom Menschen ungestörte Region mit Bergen bis zu 6.000 Metern Höhe ist wie geschaffen für Teleskope.
Der Standort auf der Südhalbkugel hat noch einen Vorteil: Von hier aus kann man ins Innere der Milchstraße blicken, auch in das schwarze Loch im Zentrum. Von der Nordhalbkugel aus lassen sich dafür weit entfernte Galaxien wie die Magellanschen Wolken beobachten.
Wenn gilt: je höher, desto besser, warum baut man dann nicht einfach mehr Weltraumteleskope?
Das ist eine Kosten-Nutzen-Frage. Weltraumteleskope haben einige Vorteile: Sie werden nicht von der strahlungsabsorbierenden Atmosphäre oder von Lichtverschmutzung auf der Erde beeinflusst. Sie können also direkt unverzerrte Bilder mit viel höherer Auflösung erzeugen. Außerdem können sie sehr schwache, weit entfernte Strahlung einfangen, die auf der Erde nicht ankommen würde. Bestimmte Strahlungen im Gamma-, Röntgen- oder Mikrowellenbereich können von der Erde aus sogar gar nicht beobachtet werden. Zudem ist ihr Blick nicht auf eine Erdhalbkugel beschränkt.
Allerdings sind Weltraumteleskope deutlich teurer, da die benötigten Materialien und der Transport ins All viel Geld kosten. Während sich die Kosten des FYST laut Astrophysiker Riechers auf einige zehn Millionen Euro belaufen werden, lag das Budget für das Weltraumteleskop Herschel Space Observatory, das die ESA 2009 ins All schickte, bei 1,4 Milliarden US-Dollar, das des James-Webb-Teleskops sogar bei 9,7 Milliarden US-Dollar.
Hinzu kommen weitere Nachteile bei der Nutzung: Weltraumteleskope müssen sehr klein sein. Das James-Webb-Teleskop zum Beispiel wurde wegen seiner Größe in der Rakete gefaltet, Teleskope wie das FYST wären zu groß, um mit den heutigen Raketen ins All gebracht zu werden. Das Herschel-Weltraumteleskop wurde mit flüssigem Helium gekühlt. Nach vier Jahren war das aufgebraucht, das Teleskop erblindete und musste 2013 abgeschaltet werden.
Denn: Einmal ins All geschossen, ist eine Reparatur oder Wartung nur noch sehr aufwendig oder – je nach Position im All – gar nicht mehr möglich. Wenn die Bedingungen auf der Erde nah genug an denen im Weltall sind, wie in der Atacama-Wüste, entscheidet man sich daher lieber gegen das Weltraumteleskop.
Teleskope auf der Erde wie im All kosten viel Geld. Rechtfertigt der Nutzen den Aufwand?
Mit sehr rudimentären Beobachtungen konnte der Astronom Nikolaus Kopernikus im 16. Jahrhundert zeigen, dass sich die Erde um die Sonne dreht und nicht umgekehrt. Das heliozentrische Weltbild war ein Schritt in Richtung Aufklärung und führte zu einem Umdenken in der Astronomie und der Wissenschaft allgemein. Seitdem haben sich Teleskope und Astronomie enorm weiterentwickelt und den menschlichen Wissensschatz erweitert.
Heutzutage geht es eher darum, die Entstehung von Sternen und Galaxien zu verstehen. So können beispielsweise Vorhersagen über die Zukunft des Sonnensystems getroffen werden: In etwa 5 Milliarden Jahren wird die Sonne ihren Brennstoff verbraucht haben, sich zu einem Roten Riesen aufblähen und die Erde verschlingen. Für die nähere Zukunft können Teleskopdaten helfen, die Wahrscheinlichkeiten von Meteoriteneinschlägen einzuschätzen.
Ein bewusst in Kauf genommener Nebeneffekt astronomischer Forschung ist auch die Entwicklung neuer Technologien. Ein bekanntes Beispiel ist das Wlan, das an einem australischen Teleskopstandort so weiterentwickelt wurde, dass es schnell und zuverlässig funktioniert. Oder Kameras und Nachtsichtgeräte.
Wie stark beeinflusst Lichtverschmutzung schon heute die Arbeit von Astronom*innen?
Laut einer Studie aus dem Jahr 2022 sind fast alle Teleskope auf der Erde von Lichtverschmutzung betroffen. Das Licht naheliegender Städte, aber auch das durch Satelliten und Weltraumschrott reflektierte Licht können die Messdaten erheblich beeinflussen. Schwache Lichtquellen – zum Beispiel die weit entfernter oder schwach leuchtender Sterne – werden eventuell gar nicht mehr wahrgenommen. Bei nur noch 6 der 28 großen Observatorien der Welt ist ein fast völlig dunkler Himmel sichtbar.
Dazu zählt die Beobachtungsstation auf dem Paranal-Berg in Chile. Doch auch dort könnte die Arbeit bald bedroht sein. Eine Tochtergesellschaft des US-amerikanischen Energieversorgers AES Corporation plant einen riesigen Industriekomplex – nur 5 bis 11 Kilometer entfernt. Das könnte einen der dunkelsten und klarsten Himmel der Erde zerstören. Noch ist der Industriepark nicht gebaut und Astronom:innen setzen sich vor Ort für eine Alternativlösung ein.
In der Submillimeter-Astronomie beeinflusst das sichtbare Licht die Ergebnisse nicht, hier ist vor allem die Atmosphäre das Problem. Aber auch Satellitenkonstellationen wie Starlink werden zunehmend zum Störfaktor, da sie in unterschiedlichen Wellenlängen strahlen und so die Messdaten verfälschen. Die Anzahl der Satelliten wird in Zukunft zunehmen.
Every month, Astronomy on Tap Köln brings you fun and enlightening talks in German and English! Join us to find what Astrophysicists are up to in solving the puzzles of the cosmos.
Make sure to show off your smarts in the exciting Pub Quiz. Winners get astronomy goodies from the European Southern Observatory, SOFIA and other cool telescopes, to take home!
Check-in now for free! or simply respond to this email with the no. of people you plan to bring to the event (not mandatory but helps us to make adequate arrangements)
Program 13.Jun 2025
“Von der Rotation zur Detektion – Der Rotations-Fingerabdruck von Molekülen” (auf Deutsch) by Dr. Luis Bonah
Der Talk handelt vom Rotations-Fingerabdruck von Molekülen, wieso er für die Detektion von Molekülen im Weltall essentiell ist, und wie wir ihn im Labor rekonstruieren können.
“Masers the original Space Lasers (or Masers, Lasers and their Creators)” (in English) by Dr. Arshia Maria Jacob
Although lasers play a vital role in our daily lives today, they were once seen as a solution in search of a problem. How did that happen? The history of the laser is a fascinating journey marked by brilliant ideas, Nobel prizes, patent disputes, and even the accidental discovery of an astronomical phenomenon. In this talk, I will guide you through this remarkable story.
In our recent A&A Letter, we studied ionized carbon emission (C⁺, [C II]) at 158 μm in S144, a C⁺ bubble on the southeastern edge of the ring-shaped star-forming region RCW79. S144 hosts a compact H II region ionized by a single O7.5–9.5 V/III star. Using SOFIA/upGREAT maps with high angular and spectral resolution, we identified the first bubble that remains mostly filled with C⁺ gas – an indicator of an exceptionally early evolutionary stage. All previously characterized C⁺ bubbles exhibit shell-like rings with central cavities carved by stellar winds, marking more advanced phases.
We also uncovered an apparent shortfall in C⁺ emission relative to S144’s far-infrared luminosity: the so-called “C⁺-deficit,” long attributed to increased dust heating, cooling via other fine-structure lines, or intense radiation fields. Our analysis shows instead that cooler C⁺ gas in the bubble’s outer layers self-absorbs the emission from its warm interior, creating the illusion of a deficit.
By correcting for C⁺ self-absorption, we refine our view of how carbon governs gas cooling in star-forming regions and improve the interpretation of [C II] observations across both Galactic and extragalactic environments.
Join us for Astronomy on Tap Bonn next week! You can attend exciting astronomy talks in English and German at Fiddlers Pub (Frongasse 9, Endenich) on Tuesday 27 at 19:00.
– “Testing Gravity with Cosmic Lighthouses” by Devika Bhatnagar (EN) – “Die dunkle Seite des Universums: ein Röntgenblick auf die Galaxienhaufen Fornax, Centaurus, Virgo und Freunde” by Prof. Thomas Reiprich (DE)
There is the opportunity to win wonderful prizes, so do not miss out!
The prize will be presented on Friday, Jun 06, 2023 from 11.00 p.m. on in a 45-60 minute ceremony.
In her PhD research, Vittoria focusses on the physics of the interstellar medium (ISM), with particular emphasis on environments at low metallicity. She has employed SILCC simulations, which model the evolution of the ISM in a stratified galactic disc. These simulations solve the ideal magneto-hydrodynamic equations and include non-equilibrium chemistry, gas heating and cooling, anisotropic cosmic ray (CR) transport, and stellar tracks. In addition, she incorporates stellar feedback through far-UV and ionizing radiation, massive star winds, supernovae, and CR injection. The gas metallicities in her simulations span from solar to as low as 0.02 Z☉, providing insights into the ISM in metal-poor galaxies.
Federico Tonielli was a PhD student at the Institute for Theoretical Physics and passed away suddenly and unexpectedly in June 2020 at the age of 27. He was a passionate character, a cosmopolitan person and an aspiring young scientist.
The award is established in his memory to enable scientific travel of a talented PhD or Master student in our Faculty. It consists of a grant of 1500 EUR in total. The successful candidate is selected by a committee consisting of representatives of the Dean’s Office and the Institute for Theoretical Physics.
The University of Bonn is a key partner in the Fred Young Submillimeter Telescope (FYST), a state-of-the-art 6-meter telescope built in North Rhine-Westphalia and now en route to its high-altitude site in Chile. This cutting-edge observatory will advance research in galaxy evolution, cosmology, and star formation, deepening our understanding of the cosmos. In this talk, I will explore FYST’s development and highlight the groundbreaking science it will enable.
Magnetic fields are a key component of the interstellar medium, influencing star formation and galaxy evolution. To better understand their structure and strength, we use data from the GLObal view on STAR formation (GLOSTAR) survey to investigate magnetic fields in the plane of the Milky Way. Our study focuses on the Faraday effect – quantified by rotation measures (RM) towards background polarized radio sources to construct the first C-band RM grid. The small channel width in wavelength squared (~1.5 to 5 cm2) at C-band makes it well suited for identifying polarized sources with extreme RMs (~3000 rad m-2 at a channel width of 200 MHz), which would likely be completely bandwidth depolarized in lower-frequency surveys. GLOSTAR’s higher frequency coverage also significantly reduces depolarization effects from foreground Galactic turbulence, enabling us to probe previously obscured, dense regions of the Galaxy.
The GLOSTAR survey covers a significant portion of the Galactic plane (-2° < l < 60° and |b| < 1°), using the Karl G. Jansky Very Large Array (VLA) in D and B array configurations and the Effelsberg 100 m telescope within the 4-8 GHz C frequency band. The data products include Stokes IQU cubes covering mosaics of 16 square degrees from VLA-D and 2 square degrees from VLA-B configuration, observed at nine distinct frequency intervals across C-band.
We detected 74 polarized sources, out of which 71 are identified in polarization for the first time, within the pilot region of the survey (28° < l < 36° and |b| < 1°) having peak-pixel percent polarization of more than 5% and greater than 7-sigma detection in polarization. We determined the rotation measure values by performing a linear fit to the multi-frequency polarization angle measurements at 9 distinct GLOSTAR spectral windows as a function of λ2. The preliminary RM grid has a source density of approximately 5 RMs per square degree which is ~ 5 times denser than the current state-of-the-art RM grid on the Galactic plane. The maximum |RM| detected is 1042.37 rad m-2, the standard deviation of the 74 RMs is 437 rad m-2 with a typical RM uncertainty of ~ 40 rad m-2.
C-band observations reveal significantly higher |RM| values and source-to-source dispersion than those seen in low-frequency surveys, offering a much more complete view of the magnetic field structure in the Milky Way. After properly quantifying wide field instrumental polarization effects, we will be able to recover more reliably polarized sources below 5% in percent polarization, resulting in an even denser RM grid. We will next apply RM synthesis to determine RMs and to resolve possible complex Faraday structures, and subsequently extend this method to encompass the entire GLOSTAR footprint, providing brand new insights into the Galactic magnetic field in Galactic quadrant 1.
Figure: The Rotation Measures of the polarized sources in the GLOSTAR pilot region, overplotted on the VLA-D + Effelsberg image. The previously reported RMs in the Consolidated RMTable (Van Eck et al. 2023) are also shown with different markers shown in the legend.
Every month, Astronomy on Tap Köln brings you fun and enlightening talks in German and English! Join us to find what Astrophysicists are up to in solving the puzzles of the cosmos.
Make sure to show off your smarts in the exciting Pub Quiz. Winners get astronomy goodies from the European Southern Observatory, SOFIA and other cool telescopes, to take home!
Check-in now for free! or simply respond to this email with the no. of people you plan to bring to the event (not mandatory but helps us to make adequate arrangements)
Program 08. May 2025
“Die direkte Umgebung unseres zentralen schwarzen Lochs Sgr A* – Eine Analyse der Vorgänge um Sgr A*” (auf Deutsch) by Dr. Florian Peissker
Das Zentrum unserer Galaxy beherbergt in supermassives schwarzes Loch. In meinem Vortrag werde ich die Umgebung und die dynamischen Prozesse vorstellen.
“Why do we need a new German Center for Astrophysics in Lusatia?” (in English) by Pavlo Plotko
This talk will be about the idea behind the DZA, explore its future science cases, and explain the reasons for building an international astrophysics center in Lusatia.
Join us for Astronomy on Tap Bonn! You can attend exciting astronomy talks in English and German at Fiddlers Pub (Frongasse 9, Endenich) on Tuesday 29 at 19:00.
– “Masers, the original space lasers (A tale of bright ideas, patents and an invention with no seemingly no use)” by Prof. Arshia Jacob (EN) – “Es gab keinen Big-Bang, wenn nicht…” by Prof. Hans Fahr (DE)
There is the opportunity to win wonderful prizes, so do not miss out!
FYST has reached its final destination on top of the Cerro Chajnantor! A film crew from the German television ZDF came along for the recent transport of CCAT/FYST in Chile from the harbor to the mountain. The Broadcast is embedded in our CCAT-documentary page:
On April 19, 2025, the delivery of FYST to the summit was completed, and April 20 Easter Sunday the bolt ring was set into place marking the start of FYST’s reassembly.
With a diameter of 100 meters, the Radio Telescope Effelsberg is one of the largest fully steerable radio telescopes on earth. Members of the CRC 1601 were invited to a tour that included beside the visitors pavilion and the observation platform also the control rooms and the first platform of telescope.
for the publication entitled “HYACINTH: HYdrogen And Carbon chemistry in the INTerstellar medium in Hydro simulations” published in Astronomy & Astrophysics in 2024. The publication describes a new sub-grid model called HYACINTH – HYdrogen And Carbon chemistry in the INTerstellar medium in Hydro simulations – for computing the non-equilibrium abundances of H2 and its carbon-based tracers, namely CO, C, and C+, in cosmological simulations of galaxy formation.
The ceremony took place during the 3rd members assembly of the CRC 1601 in Vallendar on March 27, 2025. Prachi Khatri: “I am grateful to the SFB Executive Board for recognising this work and my contribution. I thank my supervisors and collaborators for their guidance throughout the project. This research was supported by SFB956 and SFB1601, which enabled a productive collaboration between Cologne and Bonn. Finally, I sincerely thank abj-sensorik for creating this wonderful opportunity, it’s deeply encouraging as a young scientist.“
The award winner will present her work in the SFB colloquium on April 15, 2025.
The Fred Young Submillimeter Telescope is now ready to be assembled at its destination in the Atacama Desert. Planned to take up operations in April 2026, it will be able to look all the way back to the Big Bang, revealing new details about star and galaxy formation.
After a six-week ocean voyage, a week spent outside Chile’s Port of Angamos waiting to offload and another week trekking through the mountains, the first major component of the Fred Young Submillimeter Telescope (FYST) has arrived at its final home: the Cerro Chajnantor mountaintop, more than 5.600 metres above sea level.
The disassembled telescope was offloaded and trucked approximately 450 kilometres to the base of Cerro Chajnantor, in Chile’s Parque Astronómico Atacama. From there, the parts are making a careful ascent 5.600 metres to the summit, where the telescope will be reassembled to eventually begin its work studying the universe, with first light projected for April 2026. The University of Cologne is a project partner in the consortium. “I am especially delighted to be able to witness the safe arrival of the first high-tech components of the telescope on the summit after their long journey with my own eyes. We now are eager to re-assemble all the pieces, in anticipation of first light a year from now,” says Dr Ronan Higgins, astrophysicist and deputy project engineer at the University of Cologne.
FYST will be the most powerful telescope in the world for its mapping speed and sensitivity at its wavelength. It will detail star and galaxy formation from the earliest days of ‘cosmic dawn’, through ‘cosmic noon’, when most of today’s stars were formed, providing insight on cosmic inflation and gravitational waves from the very first moments of the Big Bang. It will also track the flows of gas, dust and magnetic fields across the interstellar ecosystem within galaxies.
The six-metre-diameter telescope is designed to operate at submillimetre to millimetre wavelengths. The novel optical design of FYST will deliver a high-throughput, wide-field of view telescope capable of mapping the sky very rapidly and efficiently. “We astrophysicists try to measure submillimetre radiation from the entire history of the universe, but most of the radiation cannot make it through the Earth’s atmosphere,” says Dominik Riechers, professor of observational and experimental astronomy and astrophysics at the University of Cologne. “Since FYST is too big to fit into a rocket, it is now being assembled at a location that provides us with observation conditions that are as close as possible to those in space.” The radiation is received by CHAI and PrimeCam, two unique wide-field cameras which serve as the ‘eyes’ of FYST.
“As the time for international celebration nears, we are especially aware of the significant potential that our long cooperation offers. Our world-class submillimetre telescope at, arguably, the best site in the world for its wavelength, will provide the basis for significant research by many astronomers for many years to come,” says Fred Young, Cornell University alumnus who has provided generous funding for the project over the years. The German project partners received funding from the German Research Foundation (DFG).
Although, as the driest place on Earth, the Atacama Desert is ideal for astronomical observations, reassembling the telescope at 5.600 metres will not be an easy task. Workers have to be trained and pass an exam to be registered to work at that altitude, and they can work a maximum of 12 or 13 days at a time. For each day they work at extreme altitude, they must spend a day below 2.700 metres. Casual visitors must use supplemental oxygen.
FYST is a project of CCAT Observatory, Inc., which consists of a Cornell-led collaboration, a German consortium including the University of Cologne, the University of Bonn and the Max Planck Institute for Astrophysics in Garching, and a Canadian consortium of universities led by the University of Waterloo. The telescope was built in Germany, designed and tested by CPI Vertex Antennentechnik in Duisburg and first assembled in Xanten on the Wessel GmbH premises.
Media Contact: Professor Dr Dominik Riechers Institute for Astrophysics, University of Cologne +49 221 470 76027 riechersph1.uni-koeln.de
Understanding the formation of complex organic molecules (COMs) in star forming regions is crucial for astrochemistry. Many COMs are believed to form on the surfaces of dust grains or in their ice mantles. The metallicity and dust-to-gas mass ratio in the outer Galaxy are lower than in the inner regions and are expected to influence the chemical composition of star-forming environments. To test this, we used the NOEMA interferometer to conduct a sensitive imaging spectral line survey of a hot core candidate located at a galactocentric distance of 13 kpc.
We identified 43 molecular species in the spectrum of this source, including less abundant isotopologs and deuterated species. Among them, 12 COMs containing up to ten atoms were detected in a compact (<5000 au), hot (>100 K) region. These findings confirm this source as a new hot core in the outer Galaxy, providing an excellent opportunity to study COM formation under low-metallicity conditions.
We derived rotational temperatures and column densities of the detected molecules and compared our results with simulations performed with the three-phase astrochemical code MAGICKAL. The models predict that certain molecules exhibit significantly reduced abundances (relative to methanol) at low metallicity and dust-to-gas mass ratio, while the abundances of other species remain relatively unchanged. Our observations are broadly consistent with these predictions when comparing COM abundances in this source to those in hot cores and hot corinos in the inner Galaxy. These results suggest that metallicity and the dust-to-gas mass ratio have an impact on the formation of COMs (paper in preparation).
Figure caption: part of the NOEMA spectral line survey of the new hot core in the outer Galaxy. The contributions of selected molecules to the observed spectrum are shown in various colors.
Die kosmische Hintergrundstrahlung zeigt uns das Universum, wie es nur 380.000 Jahre nach dem Urknall aussah – ein faszinierender Blick auf das „Babyfoto“ des Kosmos. In diesem Vortrag erklärt Dr. Tim-Eric Rathjen von der Universität zu Köln, was uns diese Strahlung über die Anteile von normaler Materie, dunkler Materie und dunkler Energie verrät und wie wir daraus die heutigen kosmischen Strukturen ableiten können. Ein Vortrag für alle, die sich fragen, wie wir das Unsichtbare sichtbar machen und das Gewicht des Universums bestimmen.
Du bist neugierig und interessierst Dich für Wissenschaft? Du möchtest einfach mal eine Universität erleben? Du bist in der 3. bis 6. Klasse? Dann bist Du bei der KölnerKinderUniversität genau richtig! Hier kannst Du Wissenschaft und Forschung kennenlernen, Uni-Luft schnuppern, Fragen stellen und experimentieren. Spaß und Neugier stehen bei uns im Vordergrund. Viele Wissenschaftler*innen aus unterschiedlichsten Bereichen der Universität halten die Lehrveranstaltungen extra für Kinder. Dabei ist egal, auf welche Schule Du gehst oder welche Noten Du hast.
Vortrag im Physikalischen Verein Frankfurt am 21.03.2025
Weltweit schnelles, stabiles und erschwingliches Internet – das wird mit den Megakonstellationen wie Starlink derzeit möglich. Polare Regi- onen werden erstmals ebenfalls gut abgedeckt. Aber was ist dafür nö- tig? Systeme mit tausenden Satelliten bedrohen andere Raumfahrt- anwendungen, liefern das Potenzial für eine neuerliche Zerstörung unserer Ozonschicht und machen bestimmte optische und radioastro- nomische Untersuchungen unmöglich. Was wären Alternativen?
Massive stars (M > 8 solar masses) significantly affect the surrounding medium during their life through stellar winds and ionising radiation. These processes shape the circumstellar medium (CSM) into complex structures, including cavities. When a massive star explodes as a supernova (SN), the resulting shock wave expands into this non-uniform medium, generating bright X-ray emission. As a result, X-ray observations of SN remnants (SNRs) provide insights into the stellar evolution of a progenitor massive star and the interstellar medium (ISM) nearby.
RCW 103 is a young (∼2000 years) Galactic SNR that has begun interacting with its CSM. Despite evidence of an initially asymmetric density distribution at the explosion site, its observed X-ray morphology appears almost circular with a slight asymmetry towards the southwest. The cause of this morphology remains unclear. To explore this, we perform 3D (magneto-)hydrodynamic simulations using the FLASH code, incorporating radiative cooling and self-consistent treatment of X-ray emission.
We simulate the evolution of a massive star (18 M solar masses) in a uniform ISM, including the effects of ionising radiation and stellar winds. After the SN event, we track the shock propagation and X-ray emission across multiple energy bands, similar to Chandra observations. An example of synthetic X-ray maps in the corresponding energy bands is shown in Figure 1. As the progenitor star is not stationary, the stellar wind cavity is asymmetrical, leading to a brighter X-ray emission at the edges.
This is an ongoing project that focuses on identifying the primary reason responsible for the morphology in RCW 103’s X-ray emission. Possible explanations include the progenitor star’s runaway velocity, which caused a bow shock to form, the influence of interstellar magnetic fields, or a nearby molecular cloud. Modelling these effects will improve our understanding of SNR-ISM interaction.
Die kosmische Hintergrundstrahlung wird oft als das „Babyfoto“ des Universums bezeichnet. In diesem Vortrag reisen wir fast 14 Milliarden Jahre zurück, um zu verstehen, wie diese Strahlung entstand und was sie uns heute über die Zusam- mensetzung des Universums verrät. Wir werden beleuchten, wie Astronomen und Physiker mit dieser „Momentaufnahme“ die Anteile von normaler Materie, dunkler Materie und dunkler Energie bestimmen konnten und welche Rolle diese mysteriösen Bestandteile für die Entwicklung des Universums spielen. Dr. Tim- Eric Rathjen von der Universität zu Köln gibt einen anschaulichen Einblick in die Bestandteile unseres Universums und die spannende Wissenschaft dahinter.
Stefanie Mühle, Sylvia Adscheid, Dr. Malte Tewes, Dr. Sonja Felder and Josephine Benna offered hands-on astronomy workshops at the “STEM Day 2025” of the University.
Getting more girls interested in studying mathematics and science: that is the aim of STEM Day at the University of Bonn. Numerous departments – from computer science, mathematics and physics to chemistry, geodesy, astronomy, meteorology and geophysics – offered schoolgirls a day-long opportunity to get to know their subjects and ask questions about studying.
Female students are still underrepresented in some STEM subjects (abbreviation for: mathematics, computer science, natural sciences, technology). The University of Bonn wants to counteract this and convince as many talented schoolgirls as possible to study in this field.
This year, girls and young women once again had the opportunity to get a taste of various mathematical and scientific degree courses. Under the title “STEM Day for schoolgirls”, a total of 101 schoolgirls from grades 10 to 13 took part in workshops during the all-day program, in which they experienced research and experiments up close. Lecturers and students talked to them about what drives them and gave them an impression of what studying in their respective subject might be like. The pupils also had the opportunity to exchange ideas with like-minded people and make contacts. At the end of the event, the students received a certificate of participation.
About the “Schnupper University” and the “MINT Day”
For 24 years, the University of Bonn has been organizing a taster university for schoolgirls under the title “Perspektive Math.-Nat!”. To mark its 25th anniversary, the concept of the event is being revised and is thus experiencing a creative break. In order to give interested schoolgirls an insight into the STEM subjects and to show them exciting study and career paths, individual departments at the University of Bonn have jointly decided to offer a “STEM day for schoolgirls”.
Dr. Felix Boes Akademischer Rat Institut für Informatik 4 Rheinische Friedrich-Wilhelms-Universität Bonn E-Mail: boes@cs.uni-bonn.de Telefon: +49 228 73 60555
We analyze molecules in the laboratory to find their spectroscopic “fingerprints”, which astronomers can use to identify the molecules in space. Unlike a human fingerprint, the molecular fingerprint also reveals physical properties of the molecules’ surroundings. The temperature of the astronomical regions can be determined by comparing the relative intensities of different transitions of a molecule. In an ideal case, the transitions belong to different vibrationally excited states of the molecule. Therefore, analyzing also the rotational spectra of vibrationally excited states, the so-called vibrational satellites, in the laboratory is important. However, due to the higher vibrational energy, their population usually is very much lower compared to the ground vibrational state making it harder to find their patterns in the spectrum. The figure shows a small part of the rotational spectrum of cyclopentadiene. The top row shows the predictions for the ground vibrational state in blue and the experimental data in black (maximum intensity of 800 A.U.). Going to the second row, all experimental data around the ground state predictions are removed to highlight the weaker pattern (maximum intensity of only 150 A.U.) of the vibrational state v27 with the corresponding predictions being shown in purple. Similarly, rows three and four show the spectrum after additionally removing the lines corresponding to v27 and v14, respectively. Unfortunately, a few experimental lines are missing in the last two rows as they are blended with lines of already removed states. Nonetheless, this procedure greatly facilitates the identification of vibrational satellite spectra and nicely highlights their different intensities.
Sa 15. Februar 2025, 9:00 Uhr bis Sonntag, 16. Februar 2025, 17:00 Uhr
Nach einführenden Vorträgen in die Astronomie und die Besonderheiten der Radioastronomie, sowie der dazugehörigen Messtechnik, widmen wir uns dem Bau eines einfachen Radioteleskops. JederTeilnehmende baut sein eigenes Gerät zur eigenen weiteren Verwendung. Mit dem Gerät wird es möglich sein, eine Spektrallinie von atomarem Wasserstoff bei einer Wellenlänge von 21 cm spektroskopisch zu untersuchen. Wir werden die Emission des Wasserstoffgases in der Milchstraße detektieren und über die spektrale Variation die Geschwindigkeitsunterschiede der verschiedenen Bereiche unserer Galaxie sehen. Zur Detektion der Strahlung benutzen wir ein SDR (software defined radio), das an einen Laptop-Computer angeschlossen wird. Das Teleskop wird aus einfachen Komponenten (Ofenrohr, Pappe) aufgebaut. Jeder Teilnehmende benötigt einen Laptop mit Betriebssystem Microsoft Windows. Bitte kein Tablet oder Mac. Für den Transport des Radioteleskops benötigt man am besten ein Auto. Es ist in etwa kegelförmig, ca. hüfthoch und im Durchmesser ca. 50 cm. Die anfallenden Materialkosten von ca. 140 € werden separat abgerechnet und vor Ort bezahlt. Die Veranstaltung wurde von der Hessischen Lehrkräfteakademie als dienstbezogene Fortbildungsveranstaltung akkreditiert (Veranstaltungsnummer: 0241275601). Die Gesamtdauer des Seminars beträgt 4 halbe Tage.
On 17 January, the telescope started its journey from the port of Wesel via Antwerp to its new location in Chile. With a novel optical design with 2 mirrors of diameter of six metres, innovative instruments and unique site, it will be one of the most powerful survey telescopes in the world at submm wavelenghts.
The Fred Young Submillimeter Telescope (FYST) was planned and assembled by CCAT Observatory Inc., an international scientific consortium in which the Universities of Cologne and Bonn have a 25 per cent share. It was developed by the company Vertex Antennentechnik GmbH in Duisburg, Germany. In April 2024, the telescope was set up and presented for testing on the premises of Wessel GmbH in Xanten. Since then, the components of the FYST have been disassembled and are now on their way to the telescope’s final location, the Atacama Astronomical Park, at an altitude of 5,600 metres on Cerro Chajnantor in the Chilean Atacama Desert.
The telescope has a mirror diameter of 6 metres and a surface accuracy of 10µm, making it capable to operate at submillimetre to millimetre wavelengths. The novel optical design of FYST will deliver high-throughput images with a wide field of view, enabling rapid and efficient mapping of the sky. It is intended to provide insights into the birth of the first stars after the Big Bang as well as into the formation of stars and galaxies.
Observations in the submillimetre radiation range are distorted by water vapour in the Earth’s atmosphere and the signal is greatly weakened. Since a dry location at a high altitude is required, the installation of the telescope at an altitude of 5,600 metres on Cerro Chajnantor in Chile is therefore ideal. FYST is located 700 metres above the ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope network, which is located on the Chajnantor plateau and consists of 66 parabolic antennas.
“After the successful test setup in Germany, the transport to Chile is another milestone for our unique telescope. We are now a significant step closer to the groundbreaking scientific observations we expect from FYST,” said Professor Dr Dominik A. Riechers from the University of Cologne’s Institute of Astrophysics.
Partners in the FYST project are Cornell University (USA), a German consortium including the University of Cologne, the University of Bonn and the Max Planck Institute for Astrophysics in Garching as well as a Canadian consortium of several universities.
Mit schwerem Herzen trauern wir um unseren Freund und Weggefährten Karl Menten,
der am 30.12.2024 plötzlich und unerwartet verstarb.
Grosse Dankbarkeit erfuellt uns beim Gedanken an die lange Suche
nach Wahrheit in der gemeinsamen Beobachtung der Natur.
Wir werden ihm immer ein ehrendes Andenken bewahren.
With heavy hearts we mourn the loss of our friend and companion Karl Menten,
who died suddenly and unexpectedly on December 30, 2024.
We are filled with great gratitude when we think about the long search
for truth in the common observation of nature.
We will always honor his memory.
The Public Observatory Cologne is a private institution which is run by the members of the “Vereinigung der Sternfreunde Köln e.V.” on a voluntary basis. This association of interested amateurs and amateur astronomers was founded in 1922 with the aim of disseminating basic astronomical knowledge to the public and promoting the training and further education of active amateur astronomers within the scope of the available possibilities.With the 60cm refractor “Cologne Large Telescope” (CLT) installed in 2012, the Volkssternwarte Köln operates the largest freely accessible telescope in North Rhine-Westphalia
An international team of researchers has detected a binary star orbiting close to Sagittarius A*, the supermassive black hole at the centre of our galaxy. It is the first time a stellar pair has been found in the vicinity of a supermassive black hole. The discovery, based on data collected by the European Southern Observatory’s Very Large Telescope (ESO’s VLT), helps us understand how stars survive in environments with extreme gravity, and could pave the way for the detection of planets close to Sagittarius A*.
“Black holes are not as destructive as we thought,” says Florian Peißker, a researcher at the University of Cologne, Germany, and lead author of the study published today in Nature Communications. Binary stars, pairs of stars orbiting each other, are very common in the Universe, but they had never before been found near a supermassive black hole, where the intense gravity can make stellar systems unstable.
This new discovery shows that some binaries can briefly thrive, even under destructive conditions. D9, as the newly discovered binary star is called, was detected just in time: it is estimated to be only 2.7 million years old, and the strong gravitational force of the nearby black hole will probably cause it to merge into a single star within just one million years, a very narrow timespan for such a young system.
“This provides only a brief window on cosmic timescales to observe such a binary system — and we succeeded!” explains co-author Emma Bordier, a researcher also at the University of Cologne and a former student at ESO.
For many years, scientists also thought that the extreme environment near a supermassive black hole prevented new stars from forming there. Several young stars found in close proximity to Sagittarius A* have disproved this assumption. The discovery of the young binary star now shows that even stellar pairs have the potential to form in these harsh conditions. “The D9 system shows clear signs of the presence of gas and dust around the stars, which suggests that it could be a very young stellar system that must have formed in the vicinity of the supermassive black hole,” explains co-author Michal Zajaček, a researcher at Masaryk University, Czechia, and the University of Cologne.
The newly discovered binary was found in a dense cluster of stars and other objects orbiting Sagittarius A*, called the S cluster. Most enigmatic in this cluster are the G objects, which behave like stars but look like clouds of gas and dust.
It was during their observations of these mysterious objects that the team found a surprising pattern in D9. The data obtained with the VLT’s ERIS instrument, combined with archival data from the SINFONI instrument, revealed recurring variations in the velocity of the star, indicating D9 was actually two stars orbiting each other. “I thought that my analysis was wrong,” Peißker says, “but the spectroscopic pattern covered about 15 years, and it was clear this detection is indeed the first binary observed in the S cluster.”
The results shed new light on what the mysterious G objects could be. The team proposes that they might actually be a combination of binary stars that have not yet merged and the leftover material from already merged stars.
The precise nature of many of the objects orbiting Sagittarius A*, as well as how they could have formed so close to the supermassive black hole, remain a mystery. But soon, the GRAVITY+ upgrade to the VLT Interferometer and the METISinstrument on ESO’s Extremely Large Telescope (ELT), under construction in Chile, could change this. Both facilities will allow the team to carry out even more detailed observations of the Galactic centre, revealing the nature of known objects and undoubtedly uncovering more binary stars and young systems. “Our discovery lets us speculate about the presence of planets, since these are often formed around young stars. It seems plausible that the detection of planets in the Galactic centre is just a matter of time,” concludes Peißker.
This research was presented in the paper “A binary system in the S cluster close to the supermassive black hole Sagittarius A*” published today in Nature Communications (doi: 10.1038/s41467-024-54748-3).
The team is composed of F. Peißker (Institute of Physics I, University of Cologne, Germany [University of Cologne]), M. Zajaček (Department of Theoretical Physics and Astrophysics, Masaryk University, Brno, Czechia; University of Cologne), L. Labadie (University of Cologne), E. Bordier (University of Cologne), A. Eckart (University of Cologne; Max Planck Institute for Radio Astronomy, Bonn, Germany), M. Melamed (University of Cologne), and V. Karas (Astronomical Institute, Czech Academy of Sciences, Prague, Czechia).
The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, Czechia, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.
This image indicates the location of the newly discovered binary star D9, which is orbiting Sagittarius A*, the supermassive black hole at the centre of our galaxy. It is the first star pair ever found near a supermassive black hole. The cut-out shows the binary system as detected by the SINFONI spectrograph on ESO’s Very Large Telescope. While the two stars cannot be discerned separately in this image, the binary nature of D9 was revealed by the spectra captured by SINFONI over several years. These spectra showed that the light emitted by hydrogen gas around D9 oscillates periodically towards red and blue wavelengths as the two stars orbit each other. Credit:ESO/F. Peißker et al., S. Guisard
Two stars have been found orbiting each other in the vicinity of Sgr A*, the supermassive black hole at the centre of the Milky Way. A young binary star system forming and surviving in this extreme gravity means that black holes are not as destructive as we thought. This video summarises the discovery. For more details, check: https://www.eso.org/public/news/eso2418/
Credit: ESO
The animation shows D9, the first ever star pair discovered near Sagittarius A*, the supermassive black hole at the centre of the Milky Way. We zoom in and out on the black hole and the single stars orbiting it, to then get close to D9, the first ever binary star system found in its vicinity. The video, which was made by an artist at the Brno Observatory and Planetarium, shows how the star system orbits the black hole. It also reveals the dusty gas cloud in which the star pair is enveloped, which suggests it is a young star system. The formation and survival of a binary star system in this extreme environment means that black holes are not as destructive as we thought. This animation was made possible thanks to a Czech Science Foundation Junior Star grant (GM24-10599M). Credit: P. Karas (Brno Observatory and Planetarium), RSA Cosmos Sky Explorer. Acknowledgements: M. Zajaček, F. Peißker and Czech Science Foundation
The animation shows how the two stars of the D9 star system orbit each other, enveloped in a cloud of gas and dust. The blue line indicates the orbit of the binary system around Sagittarius A*, the supermassive black hole at the centre of the Milky Way. D9 is the first ever binary star found near a supermassive black hole. Its formation and survival in this extreme environment means that black holes are not as destructive as we thought. Credit: ESO/M. Kornmesser
Contact:
Emma Bordier Institute of Physics 1, University of Cologne Cologne, Germany Tel: +49 221 470 3548 E-Mail: bordier@ph1.uni-koeln.de
Florian Peißker Institute of Physics 1, University of Cologne Cologne, Germany Tel: +49 221 470 7791 E-Mail: peissker@ph1.uni-koeln.de
Michal Zajaček Department of Theoretical Physics and Astrophysics, Masaryk University Brno, Czechia Tel: +420 549 49 8773 E-Mail: zajacek@physics.muni.cz
Markus Nielbock (Pressekontakt Deutschland) ESO Science Outreach Network und Haus der Astronomie Heidelberg, Deutschland Tel: +49 6221 528-134 E-Mail: eson-germany@eso.org
As the year draws to a close, we extend our heartfelt gratitude to all colleagues and friends who contribute to advancing our understanding of the habitats of massive stars across cosmic time. Your dedication and collaboration continue to illuminate the path forward in our shared scientific journey.
May this holiday season bring you moments of reflection and inspiration, and may the New Year provide new opportunities for discovery and progress.
Understanding how stars form and evolve is one of the most fascinating challenges in astronomy. A key piece of this puzzle is the stellar multiplicity—the frequency, separations, and mass ratios of stars that form in pairs or higher-order groups. Massive stars, which make up only 0.01% of all formed stars, play a pivotal role in shaping galaxies and the universe. Understanding their life cycle—90% of which unfolds alongside at least one companion—is therefore of paramount importance. Yet, they are particularly difficult to study since they are heavily bloated in their dusty envelopes and are born in distant, dense, and young star clusters. These observational challenges leave significant gaps in our understanding of how their multiplicity evolves over time.
To help fill this gap, our team conducted high-resolution observations to explore the properties of stars that have just formed or are still in the process of forming, within four massive, near-primordial clusters. We identify potential binary or multiple star systems, study how their properties—such as separation and mass ratios—vary within and between clusters. In this framework, multiplicity serves as a tool to trace the initial conditions that drive the formation of massive stars in multiple systems.
To study the primordial multiplicity properties, the clusters must have similar chronological ages with slight variations and be young enough to ensure that significant dynamical interactions have not yet occurred. This increases the likelihood of observing systems in a near-primordial multiplicity state. The selected clusters—Hourglass Nebula, RCW 108, DBS 113, and DBS 121—are observable in the near-infrared and submillimeter wavelengths due to their significant dust emission. These clusters are located at a distance of 1.5 ± 0.3 kpc on average and can be classified by age. Based on this cluster classification, we trace the evolution of multiplicity and companion fraction between 1.0 Myr and 2.8 Myr.
Our preliminary results are derived from NACO K-band data, with Chinmaya, a PhD student in our team, leading this aspect of the project. The figure shows one of the fields of DBS121 for which we show the identified sources, hence potential companions per bin of separation. We find that multiplicity properties evolve with cluster age, as the other clusters show a gradually increasing trend in the number of stars, thereby indicating a possible increase in companion fraction with cluster age. To extend this study, we recently included VVV CL100 (7.5 Myr) to determine whether this trend persists in older clusters.
Emma, a postdoc in our team, successfully led an ALMA proposal to enhance this analysis. Data acquisition is now underway, promising exciting new discoveries in the evolution of multiplicity properties in massive star-forming clusters. Stay tuned!
The CRC’s Sustainability Board is responsible for coordinating the evaluation of the environmental impact of the CRC’s activities and proposing measures to reduce it. In addition, the Sustainability Board organises talks and workshops for the CRC members to raise awareness of sustainability issues and establish solutions for daily work. During the sustainability barbecue on October 17, among other topics, the University of Cologne’s sustainability strategy and the problem of conference trips were discussed. In the afternoon, several workshops took place, one of which involved participants building their own insect hotels. This Thursday, a total of seven insect hotels were put up around the physics department of the University of Cologne. Insect hotels provide shelter and nesting facilities for a variety of insects during winter. Introducing insect hotels can help with pollination and ecosystem diversity.
Prachi Prajapati, an observational cosmologist working at the Max Planck Institute for Radio Astronomy and affiliated to the University of Cologne, participated in the 73rd Lindau Nobel Laureate Meeting. She reflects on her career so far and the time she spent in Lindau.
As a school kid growing up in India, I was interested in science in general. When Sunita Williams, a NASA-astronaut of Indian origin, flew to space for the first time in 2006, I closely followed the news covering that event. That interest in space science stayed with me; and having finished school, it was an apt choice to apply for a bachelor’s in Engineering Physics at the Indian Institute of Space Science and Technology (IIST), followed by a master’s degree in Astronomy and Astrophysics.
After graduation, I was immediately placed to work at the astrophysics department of the Indian Space Research Organization, where I also experienced many night shifts for observations at optical infrared telescopes on the hilltops in Western and Northern India. One of the best things was to see the Milky Way with naked eyes. The job included mainly R&D tasks, including the back-end instrumentation for ground-based telescopes. After three years, I decided to go back into academia. Since autumn 2023, I am pursuing my PhD in Bonn-Cologne, Germany, at the Max Planck Institute for Radio Astronomy.
Birth of Stars, Galaxies, Clusters and Super Clusters
Galaxies are constituted of stars, gas, dust, and dark matter. Basically, my PhD is focused on understanding the process how galaxies are formed and evolved in the history of cosmic time. Big bang is one of the most popular theories for the beginning of universe. Tracing the star formation history using the cold molecular gas lines, we are trying to find out how and when different galaxies were born after big bang, how they developed over time to become what they are at present. For analogy, it is similar to human evolution; the Darwin theory says that maybe we were monkeys and eventually we developed into the human shape as we are today – so there is a link between the two stages which is called evolution.
We observe the high-redshift galaxies using radio and submillimeter telescopes, doing multiwavelength observations of the galaxies starting from the epoch when the universe was about a few hundred million years old, until now. Eventually, the aim is to observationally understand the overall picture of the universe from the earlier epochs (high-redshift) to the stars and galaxies that we see today all around us to find out how these large structures were formed. At the same time, we all are part of the Milky Way, which itself is a part of the local cluster which is a cluster of galaxies. Now we also know of the existence of super clusters that are clusters of clusters of galaxies.
Prachi meeting Brian Josephson
The Majority of the researchers in this research field try to understand physics at all these different astrophysical scales to answer numerous open questions. This is fundamental physics, which is not immediately affecting the humanity, but it is more of a curiosity-driven research to fulfill the inner quest for understanding how the nature works. Maybe in the future it might have some societal implications – who knows?! For example, Einstein’s general theory of relativity was a pure theoretical beauty, which led to GPS applications after almost a century and now it is an integrated part of our lives.
Real Life of an Astrophysicist
Many people imagine an astronomer looking at the sky with a telescope at night – of course, that is one part of it, i.e., we have ground-based optical-infrared telescopes which are operated only at nighttime – but we also have space telescopes like James Webb Space Telescope (JWST), Hubble Space Telescope (HST) and Chandra X-ray Observatory, which are always in the sky taking observations. In addition, we also have ground-based radio-submillimeter telescopes, operating at longer wavelengths. These waves are observable also during daytime from Earth as the atmosphere is transparent for them and the sunlight in radio is not super bright, so they do not need to be observed only at nighttime. Such multiwavelength observations using different observatories provide a holistic understanding of the astrophysical targets we look at. Now with advancements in technology, most of the observatories are working automatically, and one does not have to be on-site for observations; but it is good to learn how the observations are realized. This was the reason why I visited the Karl Jansky Very Large Array (VLA) in the United States once to experience the techniques using with which the radio data for my PhD was observed. But in fact, most of the time, I am not looking through a telescope – I am sitting in front of a computer screen either coding or using software for data reduction. Not all the data we observe are perfect, so one has to remove the noises caused by unwanted radio frequency interference (RFI). For our observations, signals from mobile phones, WiFi, Bluetooth, orbiting satellites, etc. are negatively impacting the data as they also transmit similar frequencies like those we are using in radio observations. Handling large data volume is also an important aspect for all observatories, in particular for radio telescopes, as the amount of data is increasing. Upcoming radio observatories like SKA, the Square Kilometer Array in Australia and South Africa, will achieve around 700 petabytes per year.
Proposals and Future Perspectives
We receive most of the data remotely via our accounts on the observatories’ websites, for which we had submitted proposals. Proposing for observations is also a crucial part of the PhD – scientists are motivated to submit observational proposals for making new observations. This process is quite competitive because the telescopes have limited timeslots for observations and there are lots of researchers from across the world competing for them. Some of the most demanded telescopes are JWST for infrared bands, VLA for radio data, and ALMA for submillimeter. After a successful proposal and getting promising results from it, we have proposed for more observations in the coming cycle of VLA; however, due to the competitive run on the telescopes, I need to have a plan-B for my PhD. It is important to be prepared to use some other archival data to accomplish the aims of my doctoral research project, if the latter proposal does not succeed. I am particularly interested in looking at galaxies farther in distance, in the high-redshift universe, which also means that I am really probing the faintest signal that one can get from the early universe. The future in the field is promising with the latest/upcoming observatories like JWST, ngVLA, and SKA.
My plan is to go back to India as an academician and make use of my knowledge and of western collaborations to promote the field in my home country, and facilitate younger generations to conduct good science.
My Lindau Experience
One of the opportunities to connect with other scientists and the Nobel Laureates was the Lindau Meeting. I met so many people from across the globe – and I am still in touch with many of them. The interdisciplinary aspect of the Meeting amazed me. It was quite fruitful to attend the Lectures by Nobel Laureates, not only on science but also on outreach, learn how they are trying to change the academic systems in different countries and doing promotion of science. Participants were always encouraged to keep an open mind and to explore unknown fields of research. It was a perfect mix of life, philosophy, and science!
Prachi stayed with a host family: “They were super lovely and I had an amazing time discussing and exchanging science, culture, and many other topics with them.”
Additionally, I was a part of one of the Sciathon groups this year and our project got shortlisted, which meant we had the chance to discuss our project during the Sciathon Forum. This is a good platform for people who are interested in startups: talking to experts from industries and academia, getting their input or suggestions to modify things in the project – and even to be appreciated that you are doing a good work, that provides motivation to continue.
My advice to future Young Scientists: Talk with as many people as possible. Connect with them. And enjoy your time there at Lindau for a life-long experience!
Prachi Prajapati, 2024 Lindau Alumna, is conducting observational cosmology at the Max Planck Institute in Bonn, Germany. After having completed her bachelor’s and master’s degree with a major in astrophysics, she was working at the Indian Space Research Organization for about three years, before she decided to pursue her PhD. She aims to understand the early history of the universe based on the data collected by telescopes around the world.
Text and photos: Prachi Prajapati Original Article:
We are currently building the CCAT Heterodyne Array Instrument (CHAI) to be operated at the FYST-telescope. CHAI is a 64-pixel high-resolution spectrometer for two frequency bands around 460 GHz (650 µm) and 800 GHz (370 µm). For optimum instrument stability, CHAI uses balanced SIS mixers, which receive their Local Oscillator (LO) signal through an input port separate from the measurement signal input.
In order to distribute the LO power to the individual mixers, we developed a waveguide power splitter with an extremely even splitting ratio over the required bandwidth. Since the LO source is distributed to up to 32 mixers, we are employing a 5-level cascade of this divide-by-two splitter. Excessive asymmetry in the splitting ratio of a single unit would result in unacceptable power differences between the outputs of the cascade. Each of our splitting stages uses a simple Y-junction, upgraded by a drop-in chip, which suppresses crosstalk between the two outputs.
In order to illustrate the suitability of the concept for a multi-level cascade of binary splitters, we built the first section of CHAI’s LO distribution network: a 3-level cascade, which results in 8 equal output ports to serve one row of 8 mixer blocks in CHAI’s focal plane. The photograph shows a device manufactured as E-plane split block at our precision workshop. Waveguide dimensions are 0.460 mm x 0.230 mm for the low-frequency band of CHAI (420 – 510 GHz). Visible at each junction are the chips (600 µm x 60 µm) for the isolation between the output ports, which were manufactured in our microfabrication lab.
The graph shows the output power distribution measured at the 8 output ports of the 3-level cascade over the nominal bandwidth. No systematic asymmetry can be seen in the signal. The maximum power scatter – including significant measurement noise – is below 40% of the nominal output power – well within our tolerance range.
Title figure: Photograph of the two split-block halves of the 8-way power divider, showing the waveguides with the isolator chips. Output ports are numbered.
Artikel des Uni_Köln-Magazins: Bisher sind im ganzen Universum nur rund zehn mittelschwere Schwarze Löcher entdeckt worden / Das nun identifizierte Schwarze Loch führt dazu, dass sich umliegende Sterne unerwartet geordnet innerhalb eines Sternhaufens bewegen
Ein internationales Team von Forscher*innen unter Leitung von PD Dr. Florian Peißker hat einen Sternenhaufen in direkter Umgebung des supermassiven Schwarzen Lochs SgrA* (Sagittarius A Stern) im Zentrum unserer Galaxie untersucht und Anzeichen für ein weiteres, mittelschweres Schwarzes Loch gefunden. In unserem ganzen Universum sind trotz enormer Anstrengungen der Forschung bisher nur ungefähr zehn dieser mittelschweren Schwarzen Löcher gefunden worden. Wissenschaftler*innen nehmen an, dass sie sich schon kurz nach dem Urknall gebildet haben und durch Verschmelzung als „Samen“ für supermassive Schwarze Löcher fungieren. Die Studie wurde unter dem Titel „The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. II. Kinematic structure“ im Fachjournal The Astrophysical Journal veröffentlicht.
Der untersuchte Sternenhaufen namens IRS 13 liegt in einer Entfernung von 0,1 Lichtjahren vom Zentrum unserer Galaxie. Für astronomische Verhältnisse ist dies sehr nah, allerdings müsste man unser Sonnensystem dennoch zwanzig Mal von einem Ende zum anderen bereisen, um diese Strecke zurückzulegen. Den Forscher*innen ist aufgefallen, dass die Sterne, die in IRS 13 enthalten sind, sich unerwartet geordnet bewegen. Eigentlich hätten die Forscher*innen eine zufällige Anordnung der Sterne erwartet. Die geordnete Bewegung lässt zwei Schlüsse zu: Zum einen scheint IRS 13 mit SgrA* zu interagieren, was zu der geordneten Bewegung der Sterne führt. Zum anderen muss es etwas innerhalb des Sternenhaufens geben, damit dieser seine beobachtete kompakte Form behalten kann.
Multiwellenlängenbeobachtungen mit dem Very Large Telescope sowie den Teleskopen ALMA und Chandra deuten nun darauf hin, dass der Grund für die kompakte Form von IRS 13 ein mittelschweres Schwarzes Loch sein könnte, welches sich im Zentrum des Sternenhaufens befindet. Dafür würde sprechen, dass die Forscher*innen charakteristische Röntgenstrahlung sowie ionisiertes Gas beobachten konnten, das mit einer Geschwindigkeit von mehreren 100 km/s in Form eines Rings um die vermutete Position des mittelschweren Schwarzen Lochs rotiert.
Ein weiteres Indiz für die Anwesenheit eines mittelschweren Schwarzen Lochs ist die ungewöhnlich hohe Dichte des Sternenhaufens, die höher ist als jede andere bekannte Dichte eines Sternenhaufens in unserer Milchstraße. „Es scheint sich bei IRS 13 möglicherweise um einen essentiellen Baustein für das Wachstum unseres zentralen Schwarzen Lochs SgrA* zu handeln“, so Florian Peißker, Erstautor der Studie. „Dieser faszinierende Sternenhaufen überrascht die wissenschaftliche Community immer wieder, seitdem er vor rund zwanzig Jahren entdeckt wurde. Zunächst dachte man, dass es sich um einen ungewöhnlich schweren Stern handelt. Mit den hochaufgelösten Daten können wir nun aber die bausteinartige Zusammensetzung mit einen mittelschweren Schwarzen Loch im Zentrum belegen.“ Geplante Beobachtungen mit dem James-Webb-Weltraumteleskop sowie dem sich im Bau befindenden Extremely Large Telescope werden weitere Einblicke in die Vorgänge innerhalb des Sternenhaufens liefern.
Inhaltlicher Kontakt: Dr. Florian Peißker Institut für Astrophysik +49 221 470 7791 peissker@ph1.uni-koeln.de
Did you know that the University of Cologne has its own Sustainability Office? We have invited them to present their daily work and challenges to make our university more sustainable. Do you have an idea on how to improve our university? Then join us and take this opportunity to talk to them directly!
We are happy to organize fruitful discussions where you can bring your ideas how to change our work and research to make the CRC more sustainable.
We will also have a number of workshops, and we will finish with a barbecue and a quiz. We will offer drinks and a vegetarian barbecue to all participants. You are welcome to bring your own meat/other food if you wish.
As we need to plan which room to use for which workshop and we need to buy the material for the insect hotel building we ask everyone to register for their preferred workshop. Please indicate there as well whether you join for the barbecue and for the drinking so that we can buy the appropriate amounts. https://sfb1601.astro.uni-koeln.de/sustainability/sustainability-bbq/
Maria Melamed ist Doktorantin im Bereich Astrophysik an der Mathematisch-naturwissenschaftlichen Fakultät in Köln. In der Arbeitsgruppe von Prof. Dr. Eckhart setzt sie sich unter anderem mit schwarzen Löchern und Galaxien auseinander.
Neben Vorträgen zu aktuellen Forschungsthemen und Vorführungen von Experimenten kann mit Hilfe von VR-Brillen das Universum hautnah erlebt und das CCAT-Teleskop besucht werden.
Drucken Sie sich Ihre eigenen kleinen Versionen von Teleskopen (JWST, Hubble Space Telescope, CCAT) mit Hilfe von einem 3D Drucker.
Für Kinder wird der Bau von Luftraketen angeboten. Sie können ihre Raketen nach Ihren eigenen Vorstellungen und Wünschen gestalten und überlegen, wie sie ergonomisch am besten fliegen können. Als Highlight werden die Raketen zusammen fliegen gelassen.
Demonstrationsexperimente zur Laborastrophysik werden den ganzen Abend über aufgebaut sein. Mithilfe von diversen Teleskopen lassen sich Sonne, Mond und Sterne beobachten.
Wie funktioniert das ALMA Teleskop? Das ALMA Teleskop in der Atacama Wüste wird mit Hilfe von Legosteinen nachgebaut werden.
Was braucht es, um Planeten, Sterne, Galaxien und das ganze Universum in einem Supercomputer zu erschaffen? Was ist das tägliche Brot eines theoretischen Astrophysikers, und warum brauchen wir so astronomisch große Computer? Diesen und weiteren Fragen geht Dr. Tim-Eric Rathjen von der Universität zu Köln auf den Grund!
Rundwanderung zum Observatorium Hoher List, Schalkenmeeren zur langen Nacht der Astronomie am 19.10.2024 – Volker Ossenkopf-Okada
Wo kann man im Universum wandern? Auf der Erde haben wir das getan und uns auf dem Weg zum Observatorium “Hoher List” gefragt, wo wir denn noch frische Luft genießen könnten. Es gibt tausende Exoplaneten, aber könnten wir dort atmen? Die geologische Entwicklung unserer Erde hilft, diese Frage zu beantworten. Die Kombination aus Wanderung und astronomischem Beobachtungsabend erlaubt die Entstehung der Erde und die Entwicklung ihrer vulkanischen Aktivität im Kontext der Planetenentstehung und damit die besondere Stellung der Erde im Universum zu verstehen.
Die Veranstaltung bestand aus zwei separaten Teilen, die sich gegenseitig ergänzten. 34 Wanderfreunde starteten 16:30Uhr und folgten der Frage, was wir aus den Eifelmaaren über die Entwicklung anderer Planeten im Universum lernen können. Mit der Ankunft 19:00Uhr am Observatorium “Hoher List” vergrößerte sich die Besucherschar auf ca. 100 Astronomie-Interessierte, die einen Abend bei prächtigem Beobachtungswetter genießen konnten. Es gab Beobachtungsmöglichkeiten an verschiedenen Teleskopen, einen Vortrag zu den Besonderheiten des Abends, d.h. dem Kometen C/2023 A3 Tsuchinshan-ATLAS, dem Saturn und dem Mond bei den Plejaden. Daneben konnte die historische Instrumentensammmlung und der Lernraumes “Erläuterung der Himmelsmechanik” besichtigt werden.
Höhepunkt des Abends waren natürlich die Beobachtungen des Kometen Tsuchinshan-ATLAS, den man sowohl mit bloßem Auge, als auch mit den verschiedenen Teleskopen, wie dem neuen computergesteuerten Celestron bewundern konnte. Tatkräftige Unterstützung gab es dabei von der Astronomie AG des Johannes-Gymnasiums Lahnstein, die verschiedene Teleskope vor dem Turm 1 installiert hatte. Besonderes Interesse gab es für den Bonner Doppelrefraktor aus dem Jahr 1899 im Turm 5. Ein Blick auf das Mond-Spekrum mit dem DADOS-Spektrometer schloss den Kreis zum Start der Wanderung und der Frage nach der Zusammensetzung extraterrestrischer Atmosphären.
To date, the growth mechanism of supermassive black holes (SMBHs) is a scientific mystery. If we consider the accretion rate of the SMBH in our Milky Way, Sagittarius A* (Sgr A*), and the age of the universe, a discrepancy of several magnitudes in its mass opens up. One proposed idea to overcome the mismatch of accretion rate and age of the universe is merging events between intermediate-mass black holes (IMBHs) that ultimately form SMBHs. However, only around 10 IMBHs in our entire universe have been confirmed by observations, which poses a significant challenge to the theory of merging black holes. In Peißker et al. (2023c) and Peißker et al. (2024b), we have analyzed the densest stellar cluster, IRS 13, in our Milky Way, only about 0.3 lightyears away from Sgr A*. This massive embedded cluster shows two distinct generations of stars, implying independent and plausible triggered, star formation events. Until recently, it was unclear how and why this cluster so close to an SMBH seems to preserve its shape. As we show in both related publications, the cluster comprises three distinctive components. One of the components is associated with the dense core of the cluster, whereas the other one shows signs of evaporation. We argue that IRS 13 is the remanent of a more massive cluster that plunges into the gravitational well of our central SMBH. One key aspect of this analysis is the young age of the two stellar populations. From the young age and plausible star formation channels, we derive an unusually short cluster migration timescale. One explanation for the rapid infall of the cluster could be the presence of an IMBH inside the cluster. In Peißker et al. (2024b), we confirm that the presence of an IMBH is highly likely. Due to the evaporation nature of the cluster, it is expected that we identified one of the first pre-merger setups between an SMBH and IMBH to date.
Das Universum besteht zu 95 Prozent aus zwei mysteriösen, unsichtbaren Komponenten, der Dunklen Materie und der Dunklen Energie. Eines der Hauptziele der Kosmologie ist es, diesen Bestandteilen auf die Spur zu kommen und ihre Eigenschaften einzugrenzen. In diesem Vortrag werde ich die zugrundeliegenden Methoden erläutern und einen Überblick über die Durchmusterungen geben, die uns einen neuen Blick und neue Erkenntnisse über unser Universum geben werden.
A public talk during the Meeting of the Astronomical Society 2024
Andrina Nicola Universität Bonn, Argelander Institut für Astronomie
Thursday, 12 September 2024, 20:00, Aula, University of Cologne
Stars form within molecular clouds, dense regions of cold gas primarily composed of molecular hydrogen. These clouds provide the necessary conditions for the formation of stars, including low temperatures and high densities, which allow gravitational forces to overcome thermal pressure and initiate the collapse of gas. To fully understand the process of star formation and therefore the evolution of galaxies, it is crucial to study the properties of molecular clouds—such as their mass, density, distribution, and relation to the galactic environment.
The Physics at High Angular resolution in Nearby GalaxieS (PHANGS) collaboration aims to create a comprehensive view of star formation and the lifecycle of gas and dust in nearby galaxies, using state-of-the-art facilities. In particular, by leveraging the James Webb Space Telescope (JWST)’s infrared capabilities, the PHANGS-JWST program has provided astonishing views of 19 galaxies in wavelengths that are typically obscured by dust in the optical range, reaching unprecedented resolutions and sensitivities.
We used observations of the emission from Polycyclic Aromatic Hydrocarbons (PAHs, e.g. complex organic molecules that emit strongly in the mid-infrared and are associated with photodissociation regions) from PHANGS-JWST to generate molecular gas maps of the 19 galaxies.
The application of the Spectral Clustering for Molecular Emission Segmentation (SCIMES) on the JWST data allowed the identification of more than 50,000 highly-resolved molecular clouds. SCIMES is a machine learning-based code that utilises graph theory concepts to segment out molecular clouds from the more diffuse medium by preserving their intrinsic morphology and internal structure.
Our preliminary results suggest that the molecular cloud mass spectra—specifically their steepness and truncation mass—are strongly influenced by the surrounding dynamical environment. This indicates that certain physical conditions may be more favourable to the formation of high-mass clouds than others.
Figure caption: Upper row: Left image shows the galaxy’s intensity map; right image displays dust structures identified by SCIMES with a greyscale intensity background and a colour bar indicating 7.7 μm intensity. Bottom row: Cumulative mass distributions of molecular clouds in different environments. Dotted black lines represent simple power-law fits; solid black curves are truncated power-law fits. Fit parameters—γ (spectral index), M0 (maximum mass), N0 (count in the distribution). The grey region represents the Poisson errors on the counts.
Line Intensity Mapping (LIM) is an emerging technique in radio-astronomy that scans vast fractions of the sky with a large beam and detects the integrated emission of all sources along the line of sight without resolving individual objects. This approach enables probing the high-redshift Universe including the contribution from intrinsically faint sources that traditional surveys miss due to their flux-limit thresholds. These peculiarities make LIM an ideal tool to probe the nature of dark matter (DM).
Most particle-physics candidates for DM fall into the class of thermal relics (i.e. particles that were once in thermal equilibrium with the rest of the Universe). In this case, the velocity dispersion of the particles at early times turns out to be inversely proportional to their mass. This implies that less massive particles can freely stream out of shallow potential wells and, de facto, inhibit the formation of low-mass structures. Therefore, cold DM (CDM, with negligible velocity dispersion) and warm DM (WDM, with a free-streaming length of the order of 0.1 Mpc) give rise to a different mass spectrum of DM halos within which galaxy formation takes place.
Using the halo-model approach, we make forecasts for the constraints that LIM of the 150 μm fine-structure transition of [Cii] can set on the mass of the DM particles. Ionised carbon is a promising tracer that should be present also in low-mass halos, contrary to neutral hydrogen that cannot be shielded from the UV background after cosmic reionisation. We compress the data into the isotropic power spectrum and use Bayesian inference marginalising over the uncertain faint-end slope of the [Cii] luminosity function (LF).
Our results are shown in the figure as a function of the survey area and for two different measurements of the bright-end of the [Cii] LF (optimistic/pessimistic). Assuming a CDM scenario, we find that LIM can rule out WDM particle masses up to 2–3 keV, which makes this technique competitive with other probes, such as the Ly-α forest. Our study demonstrates that, taking into account the current limits on the LF, the [Cii] power spectrum is dominated by sources hosted in relatively massive halos and this diminishes its constraining power on the WDM mass.
Modelling the molecular gas content of galaxies is a highly non-linear, multi-scale problem in astrophysics. On one hand, it is necessary to simulate galaxies in realistic environments as they are affected by outflows and gas accretion from the cosmic web. On the other hand, molecular-cloud chemistry is regulated by conditions on sub-parsec scales.
To overcome this challenge, we have developed a new sub-grid model, HYACINTH – HYdrogen And Carbon chemistry in the INTerstellar medium in Hydro simulations – that can be embedded into cosmological simulations of galaxy formation to calculate the non-equilibrium abundances of molecular hydrogen and its carbon-based tracers, namely, CO, C, and C+ on the fly. Our model captures the effects of the ‘microscopic’ (i.e., unresolved) density structure on the ‘macroscopic’ (i.e., resolved) chemical abundances in cosmological simulations using a variable probability distribution function of sub-grid densities within each resolution element.
The chemical abundances from HYACINTH are in good agreement with observations of nearby and high-redshift galaxies. We are now running a suite of cosmological galaxy formation simulations with HYACINTH that will allow us to address fundamental questions regarding the contribution of different galaxies to the global H2 budget and the reliability of different molecular gas tracers across ISM conditions and galaxy environments at high redshifts (z ≳ 3).
Figure caption: Column density maps of different species in a pre-simulated galaxy (from Tomassetti et al. 2015) post-processed with HYACINTH. The first two panels show the distribution of total and molecular hydrogen from the simulation, while the other panels show the species obtained in post-processing. CO is concentrated in regions with the highest N(H2), while C and C+ are more widespread; C+ even extends out to regions lacking a significant amount of H2and closely mirrors the total gas distribution.
Our science is often not visible to the public because we don’t know how to present in properly. With the help of the UoC press department we are aiming to change that.
A first seminar about science communication will be on Monday, June 24 at 3 pm (regular colloquium time). All PH1 or SFB1601-members are invited to join, there is no registration necessary.
Forschungsmeldung der Universität zu Köln: Die jungen Sterne umrunden das Schwarze Loch im Zentrum unserer Galaxie mit mehreren 1000 km/s / Veröffentlichung in Astronomy & Astrophysics
Astronomische Beobachtungen zeigen, dass sich neu entdeckte Babysterne in der Umgebung von Sagittarius A*, dem Schwarzen Loch im Zentrum unserer Galaxie, anders verhalten als erwartet: Sie beschreiben ähnliche Bahnen wie bereits bekannte Hochgeschwindigkeitssterne und ordnen sich in einem bestimmten Muster um das Schwarze Loch an. Die Studienergebnisse deuten darauf hin, dass Sgr A* die Sterne zu bestimmten Anordnungen veranlasst. Die Studie wurde unter dem Titel „Young Stellar Objects in the S-cluster: The Kinematic Analysis of a Sub-population of the Low-mass G-objects close to Sgr A*“ in der Fachzeitschrift Astronomy & Astrophysics veröffentlicht. Beteiligt waren Forscher*innen der Universität zu Köln, der Masaryk-Universität in Brünn (Tschechien), der Karls-Universität in Prag (Tschechien), der Akademie der Wissenschaften der Tschechischen Republik und des Max-Plack-Instituts für Radioastronomie in Bonn.
Vor rund dreißig Jahren wurden in der direkten Umgebung des supermassiven Schwarzen Lochs Sgr A* im Zentrum der Milchstraße Hochgeschwindigkeitssterne entdeckt. Diese Sterne, auch S-Sterne genannt, umrunden das Schwarze Loch mit Geschwindigkeiten von mehreren 1000 km/s in wenigen Jahren. Die Sterne sind überraschend jung und ihre Anwesenheit rätselhaft, denn nach gängigen Theorien würde man nur alte und leuchtschwache Sterne in der unmittelbaren Umgebung eines Schwarzen Lochs erwarten.
Die technologischen Fortschritte der letzten Jahrzehnte und die lange Beobachtungszeit des galaktischen Zentrums durch moderne Teleskope werfen aktuell noch weitere Fragen auf. So wurde zum Bespiel im Jahr 2012 ein Objekt entdeckt, bei dem Wissenschaftler*innen von einer Gaswolke ausgingen, die vom Schwarzen Loch „aufgesaugt“ wird. Zwar hat sich die These nicht bestätigt, es war aber lange Zeit nicht klar, um was es sich genau bei diesem Objekt handeln könnte. Erst in den letzten Jahren verdichten sich die Anzeichen, dass es ein sehr junger Babystern sein könnte, umgeben von einer staubigen Wolke.
Inklusive dieses Babysterns untersuchten die Wissenschaftler*innen für die aktuelle Studie ein Dutzend Objekte in der direkten Umgebung des supermassiven Schwarzen Lochs, die alle sehr ähnliche Eigenschaften aufweisen. Sie fanden heraus, dass die Objekte nochmals deutlich jünger sind als die bereits bekannten Hochgeschwindigkeitssterne. „Interessanterweise verhalten sich diese jungen ‚Babysterne‘ aber so wie die S-Sterne. Das bedeutet, auch die Babysterne umrunden das Schwarze Loch mit mehreren 1000 km/s in wenigen Jahren“, so Dr. Florian Peißker vom Institut für Astrophysik der Universität zu Köln und Erstautor der Studie. „Bereits die S-Sterne sind überraschend jung. Nach gängigen Theorien ist die Anwesenheit eines stellaren Kindergartens mit den noch jüngeren ‚Babysternen‘ völlig unerwartet,“ fügt Dr. Peißker hinzu.
Es zeigte sich weiterhin, dass dieser Sternenhaufen, bestehend aus den Babysternen und den S-Sternen, auf den ersten Blick wie ein chaotischer Bienenschwarm aussieht. Wie ein Schwarm weist aber auch der Sternenhaufen Muster und Regelmäßigkeiten auf. So konnten die Forscher*innen zeigen, dass sich die Babysterne wie die S-Sterne auf bestimmte und geordnete Weise im dreidimensionalen Raum anordnen. „Das bedeutet, es gibt gewisse präferierte Orientierungen der Sterne. Die Verteilung beider Sternvarianten gleicht dabei einer Scheibe, was den Eindruck nahelegt, dass das Schwarze Loch Sterne dazu zwingt, sich in geordneten Bahnen anzusiedeln“, so Peißker.
The Near- and Mid-infrared observation of dusty sources in the S cluster, which harbors the supermassive black hole in the center of our galaxy, Sgr A*, is accompanied by a discussion about their nature. The current study, published today in A&A, aims to explore the Keplerian parameters of these dusty S cluster members orbiting Sgr A* and analyze their orbital distribution. The results indicate a clear disk-like pattern following the arrangements of the main-sequence cluster members, suggesting a common formation process for the young dusty sources. Based on the multi-wavelength photometric analysis, the study found strong indications that suggest that the dusty sources have a stellar nature consistent with the spectral energy distribution of Young Stellar Objects. The nature of the dusty sources and their organized arrangement around Sgr A* are unexpected and shed light on unexplored star formation processes in the high energetic radiation environment of the supermassive black hole.
Published in A&A (2024)
Context: The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. Until now, the question of the origin of these two populations is vague, although all explanations favor migration processes for the individual cluster members. Aims: This work revisits the S-cluster and its dusty members orbiting the supermassive black hole Sgr A* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a non-random distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods: Based on the photometric analysis, we estimated the individual H − K and K − L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a Young Stellar Object Class I model. We obtained the position angle from the Keplerian fit results, and additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results: The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and mid-infrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of Sgr A* are much shorter (≪ 2 years) than the epochs covered by the observations (≈15 years). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions: The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and the longitudes of the ascending node, strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share the common formation history or migrated with a similar formation channel in the vicinity of Sgr A*. Alternatively, the gravitational influence of Sgr A* in combination with a massive perturber, such as a putative IMBH in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement.
Many places in space are too far away to learn about them by sending spacecraft there. So they cannot be examined directly but instead, we can learn about them by analyzing their emitted light. Due to quantum mechanics, each molecule has a set of characteristic transition lines that uniquely identify it. When these transition lines are found in the emitted spectrum, we can be sure that the respective molecule appears in the observed object. However, to identify molecules in space, we first have to understand their characteristic patterns in the laboratory. We do so by measuring the rotational spectrum of the molecules in our experiment and then fitting quantum mechanical models to them. These models can then be used by astronomers to identify the molecules in space and also to infer the physical conditions of the corresponding regions in space. For example, the temperature can be deduced from intensity relations, the pressure from the lineshape, and the molecule’s abundance can be inferred from its intensity. Here, we measured the pure rotational spectrum of phosphabutyne (C2H5CP) for the first time and analyzed its vibrational ground state as well as its three singly 13C-substituted isotopologues. This will allow astronomers to search for phosphabutyne in space and determine the prevailing conditions of the corresponding regions. The figure shows a section of the measured broadband spectrum on top, highlighting the pattern repeating with the total angular momentum quantum number J, while the zoom-in on the bottom highlights the very good agreement between the calculated and measured spectrum, especially when applying a small shift of 126 MHz. This work was performed in collaboration with Jean-Claude Guillemin (University Rennes) and Michael E. Harding (KIT).
What is the structure and chemical composition of gas that may feed future star formation? Before interstellar gas turns dense enough to form new stars it is not fully molecular yet but in some so far unknown transitional state. A special case of such gas clouds are given by high-latitude clouds representing material that may fall onto the plane of the Milky Way. In a recently accepted paper by Nicola Schneider and collaborators we reported results from SOFIA/upGREAT observations of a number of diffuse and high latitude clouds in the Milky Way, in particular the Draco, Spider, Polaris and Musca clouds. In only one of them, the Draco cloud, we detected emission of ionized carbon in spite of it being neither the densest cloud nor the one irradiated the strongest by known sources. When trying to model the emission of all observations in terms of an astrochemical model of a photon-dominated region it turns out, that the model is not able to simultaneously explain the strength of the continuum emission from dust and the ionized carbon line. The ionized carbon detection and also the non-detections suggest a very low impinging UV field well below what is actually observed taking all the known stars in the environment. For the Draco cloud we can explain the difference by the additional energy from a shock that is produced when the cloud is hitting the interstellar gas of the Milky Way and some shielding of the cloud by interstellar dust in atomic gas. However, for the other clouds, we do not have a consistent explanation yet. The paper combined the results from a fruitful collaboration between the CRC 1601 subprojects B2 and A6.
Figure caption: Schematic illustration of the illumination of a high-latitude cloud by UV radiation from stars in the plane of the Milky Way. The orange cylinder along the path between star and cloud indicates the dust column which attenuates the UV-field.
The Kleinmann-Low nebula in the Orion is a location of intense star formation with a complex spatial and chemical dynamic. Its radiation originates from finely distributed atoms and molecules, which in the light of the young stars emit a characteristic spectrum. The piece „Leuchtstoffraum“ is informed by the unusually precise measurements of the Herschel space telescope from 2010. It is based on the simple principle that the natural laws are the same on earth as in the nebula 1300 light years away. We hear the structure of electromagnetic radiation of a minute point in the sky whose frequencies may be partitioned into series of molecule spectra, known from the laboratory. Leuchtstoffraum 2 is an outcome of a collaboration between Julian Rohrhuber, professor at the Robert Schumann Hochschule Düsseldorf, with the astro-physicist PD Dr. Volker Ossenkopf-Okada, who teaches at I. Physikalische Institut of the University, Cologne.
Pressemitteilung der Universität zu Köln: Am 04. April 2024 wurde das neue Fred Young Submillimeter Teleskop (FYST) in Xanten am Niederrhein präsentiert. Begleitet von Vorträgen zu den wissenschaftlichen und technischen Hintergründen konnten sich die Teilnehmer*innen bei einer Bewegungsdemonstration und in Führungen einen Eindruck von dem neuartigen Teleskopdesign machen. Das FYST ist ein hochmodernes Teleskop, dessen Spiegeldurchmesser allein sechs Metern misst. Damit ist es für den Betrieb im Submillimeter- bis Millimeter-Wellenlängenbereich ausgelegt. Es wird Einblicke in die Geburt der ersten Sterne nach dem Urknall sowie in die Entstehung von Sternen und Galaxien gewähren.
„Das neuartige optische Design wird Aufnahmen mit hohem Durchsatz und großem Sichtfeld liefern und so eine schnelle und effiziente Kartierung des kompletten Himmels der südlichen Hemisphäre ermöglichen. Wir versuchen nicht weniger, als die Entstehung und Entwicklung unseres Universums seit dem Urknall besser zu verstehen“, so Professor Dr. Dominik Riechers vom Institut für Astrophysik der Universität zu Köln. „Es ist schon etwas ganz Besonderes, dass sich Universitäten, wie hier die Unis Bonn und Köln, an der Bereitstellung einer so großen wissenschaftlichen Infrastruktur beteiligen können. Das ist nur durch eine langjährige Schwerpunktsetzung möglich. Wir danken allen Förderern und Konsortiumspartnern“, sagte Karsten Gerlof, Kanzler der Universität zu Köln. Zudem richteten unter anderem Professorin Dr. Stephanie Walch-Gassner (Präsidentin der Astronomischen Gesellschaft, Institut für Astrophysik der Universität zu Köln), Thomas Görtz (Bürgermeister der Stadt Xanten), Edeltraud Klabuhn (Bürgermeisterin der Stadt Duisburg) und Chapman Godbey (US-Generalkonsulat Düsseldorf) Grußworte an die Teilnehmer*innen.
Nach dem Event wird das FYST zunächst weiterentwickelt. Zum Jahresende wird es demontiert und in Einzelteilen nach Chile verschifft. Final wird es in 5.600 Metern Höhe auf dem Berg Cerro Chajnantor in der chilenischen Atacama-Wüste stehen und das Atacama Large Millimeter/submillimeter Array (ALMA) überblicken. Die Beobachtungen des Weitwinkel-Teleskops im Submillimeter-Strahlungsbereich werden durch Wasserdampf in der Erdatmosphäre leicht verzerrt und das Signal stark abgeschwächt. Daher wird ein hoher und trockener Standort benötigt.
Partner im Projekt sind die Cornell University (USA), ein deutsches Konsortium bestehend aus der Universität zu Köln, der Universität Bonn und dem Max-Planck-Institut für Astrophysik in Garching sowie ein kanadisches Konsortium mehrerer Universitäten. Entworfen wurde das Teleskop von Vertex Antennentechnik in Duisburg. Montiert wurde das FYST in Xanten auf dem Gelände der Wessel GmbH. Benannt wurde es nach Fred Young, der das Projekt über viele Jahre begleitet und großzügig finanziell unterstützt hat.
Stellar feedback refers to the processes by which massive stars release energy, radiation, and material into their surroundings, influencing the structure and evolution of the galaxies in which they reside. Understanding the impact of stellar feedback on different galactic environments is crucial for developing a comprehensive picture of galaxy formation and evolution. In this context, different galactic environments refer to regions within a galaxy that differ in their physical conditions, such as the average gas density, temperature, metallicity, or radiation field.
I will present results from the SILCC (SImulating the Life-Cycle of molecular Clouds) project, in which we study the evolution of the multi-phase interstellar medium in parts of galaxies. In particular, we use these modern three-dimensional simulations to unravel the relative impact of stellar winds, ionizing radiation, and supernovae on the surrounding interstellar gas. From the galactic scale simulations, we find that ionizing radiation is the most important physical process for regulating the star formation rate, while supernovae overpressure the gas substantially, thus driving a galactic outflow. I will show how the star formation process ongoing in the Milky Way and other galaxies can be quantified with these multi-physics numerical simulations.
What roles do different stellar feedback processes play in governing star formation? From ionizing and non-ionizing
radiation to stellar winds and supernovae, these forces interact with the surrounding stellar nurseries. However,
understanding the precise significance of each process in shaping star formation remains an ongoing challenge.
We present new magneto-hydrodynamic (MHD) simulations conducted within the SILCC framework, exploring the multiphase interstellar medium
(ISM) within a patch of a stratified galactic disk. Our study incorporates a self-consistent modeling of
non-ionizing far-ultraviolet (FUV) radiation emitted by stellar clusters, aiming to understand its impact on star
formation and the chemical composition of the nearby ISM. We observe locally intense interstellar radiation fields
(ISRF) with values up to G0 ≈ 104 (in Habing units), contrasting with the canonical solar
neighborhood value of G0 = 1.7.
Our findings suggest that while FUV radiation influences star formation, its role in regulating the star formation
rate (SFR) appears less significant compared to other stellar feedback mechanisms such as ionizing UV radiation,
stellar winds, and supernovae. Additionally, our chemical analysis reveals enhancements in both the warm-ionized
medium (WIM) and the cold-neutral medium (CNM) beyond the vicinity of stellar clusters, indicating a complex
interplay influenced by the self-consistent and highly variable FUV radiation field, fostering the presence of a
diffuse molecular hydrogen gas phase.
Further details will be available in Rathjen et al., currently in preparation.
Figure:
Overview of the simulated ISM. Shown are the edge-on views of the total gas (Σgas, 1st panel), molecular
hydrogen (ΣH2, 4th panel), and ionized hydrogen (ΣH+, 5th panel) column
densities, as well as mass-weighted gas (Tgas, 2nd panel) and dust (Tdust, 3rd panel)
temperatures and ionizing photon energy density (eγ, 6th panel), the effective G0 field
(Geff, 7th panel), and cosmic ray energy density (eCR, 8th panel) in projection. The
star-forming galactic ISM is concentrated around the midplane. White circles in the 1st panel indicate active star
clusters.
Am 22. März um 20:00 Uhr in der Volkssternwarte Köln (Theaterkeller des Schiller-Gymnasiums)
Unsere kosmische Umgebung ist geprägt von unzähligen Sternen, die in den Tiefen des Weltraums entstehen. Doch wie genau formen sich diese strahlenden Himmelskörper, und wie entstehen die Planetensysteme, die sie umgeben?
In diesem Vortrag werden wir uns auf eine Reise durch die Geburt von Sternen begeben und die komplexen Prozesse erkunden, die zur Entstehung neuer Planetensysteme führen. Wir werden erfahren, dass Sternentstehung in gigantischen Gas- und Staubwolken stattfindet, in denen Gravitationskräfte und elektromagnetische Strahlung eine Schlüsselrolle spielen. Wir werden uns mit der Kollapsphase bis zur Geburt eines leuchtenden Sterns auseinandersetzen sowie die Entstehung von Planeten und deren Anordnung in einer Vielzahl von Planetensystemen erforschen.
Online-Tickets: 7 € / 4 € (Erm. für Studierende): https://pretix.eu/volkssternwartekoeln.de Vereinsmitglieder genießen für ihren Jahresbeitrag 60 € / 30 € (Erm. für Studierende) freien Eintritt bei allen unseren Veranstaltungen! (Ihre Online-Tickets reservieren dann nur Plätze)
Jülich Supercomputing Centre offers a training programme of about 25 HPC-relevant courses per year. The courses comprise lectures and hands-on training on programming languages, usage of HPC systems, parallel environments, MPI, hybrid programming, GPU programming, deep learning, and – in the near future – quantum computing.
To learn more about the formation and evolution of massive stars it is important to confront simulations and observations. It is useful to interpret the observational data and to extract the cores’ physical parameters,. We can address e.g. the question how massive cores fragment and form (massive) stars, or how long the young, massive stellar objects are embedded in their parental core.
Doing so, we simulate a collapsing core scenario of a subvirial, 1000 M☉ core with an initial radius of 1 pc and a linear magnetic field of 100 μG, which is a birthplace of massive stars.
For the post-processing we use RADMC-3D, which is an open source radiative transfer code that is based on the Monte-Carlo method. Here, we present synthetic observations of the dust emission (top left panel). The advantage of our simulations is that we calculate the dust temperature self-consistently, hence taking into account radiative heating by all young stars as well as shock heating. Thus, RADMC-3D is directly working on the simulated dust temperature. These results are post-processed with CASA, where different, respectively a combination of, possible ALMA channels and predictable water vapour (pwv) in the atmosphere can be simulated. We show the results for synthetic observations in different ALMA channels (labeled with AMLA TM1, TM2 and ACA; bottom panels), as well as their combination for two predictable water vapour settings (top middle and top right panel). In synthetic observations most of the structures in the less dense environment are not visible anymore; however, the emission of the main star forming regions remain.
This work was performed in collaboration with Dr. Álvaro Sánchez-Monge
Physikalischer Verein Mi., 22. Nov. 2023 19:30 Uhr bis 20:30 Uhr Livestream
Unsere kosmische Umgebung ist geprägt von unzähligen Sternen, die in den Tiefen des Weltraums entstehen. Doch wie genau formen sich diese strahlenden Himmelskörper, und wie entstehen die Planetensysteme, die sie umgeben? In diesem Vortrag werden wir uns auf eine Reise durch die Geburt von Sternen begeben und die komplexen Prozesse erkunden, die zur Entstehung neuer Planetensysteme führen.
Wir werden erfahren, dass Sternentstehung in gigantischen Gas- und Staubwolken stattfindet, in denen Gravitationskräfte und elektromagnetische Strahlung eine Schlüsselrolle spielen. Wir werden uns mit der Kollapsphase bis zur Geburt eines leuchtenden Sterns auseinandersetzen sowie die Entstehung von Planeten und deren Anordnung in einer Vielzahl von Planetensystemen erforschen.
Durch modernste astronomische Beobachtungen und Simulationen haben Wissenschaftler bedeutende Erkenntnisse über diese Prozesse gewonnen. Ich werde einige der neuesten Entdeckungen und bahnbrechenden Forschungsergebnisse präsentieren, die unser Verständnis von Sternen und Planetensystemen vertiefen.
Vortrag von Slawa Kabanovich (PH1): Sternentstehung im Eiltempo – Fliegende Sternwarte SOFIA liefert überraschende Ergebnisse
Beobachtungen des ionisierten Kohlenstoffs mit dem upGREAT (German Receiver for Astronomy at Terahertz) an Bord des deutsch-amerikanischen Stratosphärenteleskops SOFIA (Stratosphären-Observatorium für Infrarot-Astronomie) haben gezeigt, dass HII-Regionen sich rasch ausdehnen können, angetrieben durch den Sternenwind. Die Kompression des umgebenden interstellaren Materials initiiert die Entstehung neuer Sterne. Dabei konnten wir feststellen, dass die Sternentstehung auf viel kürzeren Zeitskalen erfolgen kann, als bisher angenommen wurde. Die Beobachtung des ionisierten Kohlenstoffs war ausschließlich durch SOFIA möglich, da die [CII]-Linie vom Erdboden aus nicht beobachtbar ist. Die analysierten Daten ermöglichten es uns, die Bildung interstellarer Wolken zu untersuchen, und darüber hinaus den Einfluss massereicher Sterne auf das interstellare Medium zu erforschen.
Monatsvortrag am 24.11.2023 um 20:00 Uhr in der Volkssternwarte Köln:
An unexpectedly high number of young stars has been identified in the direct vicinity of a supermassive black hole and water ice has been detected at the centre of our galaxy / publication in “The Astrophysical Journal”
An international team led by Dr Florian Peißker at the University of Cologne’s Institute of Astrophysics has analysed in detail a young star cluster in the immediate vicinity of the supermassive black hole Sagittarius A* (Sgr A*) in the centre of our galaxy and showed that it is significantly younger than expected. This cluster, known as IRS13, was discovered more than twenty years ago, but only now has it been possible to determine the cluster members in detail by combining a wide variety of data – taken with various telescopes over a period of several decades. The stars are a few 100,000 years old and therefore extraordinarily young for stellar conditions. By comparison, our sun is about 5 billion years old. Due to the high-energy radiation as well as the tidal forces of the galaxy, it should in fact not be possible for such a large number of young stars to be in the direct vicinity of the supermassive black hole. The study was conducted under the title ‘The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. I. Detection of a Rich Population of Dusty Objects in the IRS13 Cluster’ and has now appeared in The Astrophysical Journal.
In connection with the current study, a further outstanding result has also been published. For the first time, the James Webb Space Telescope (JWST) was used to record a spectrum free of atmospheric interference from the Galactic Center. A prism on board the telescope was developed at the Institute of Astrophysics in the working group led by Professor Dr Andreas Eckart, a co-author of the publication. The present spectrum shows that there is water ice in the Galactic Center. This water ice, which is often found in the dusty discs around very young stellar objects, is another independent indicator of the young age of some stars near the black hole.
In addition to the unexpected detection of young stars and water ice by the JWST, the researchers led by Dr Peißker have also found that IRS13 has a turbulent history of formation behind it. The study results suggest that IRS13 migrated toward the supermassive black hole through friction with the interstellar medium, collisions with other star clusters, or internal processes. From a certain distance, the cluster was then ‘captured’ by the gravitation of the black hole. In this process, a bow shock may have formed at the top of the cluster from the dust surrounding the cluster, similar to the tip of a ship in the water. The associated increase in dust density then stimulated further star formation. This is an explanation why these young stars are above all in the top or front of the cluster.
“The analysis of IRS13 and the accompanying interpretation of the cluster is the first attempt to unravel a decade-old mystery about the unexpectedly young stars in the Galactic Center,” according to Dr Peißker. “In addition to IRS13, there is a star cluster, the so-called S-cluster, which is even closer to the black hole and also consists of young stars. They are also significantly younger than would be possible according to accepted theories.” The findings on IRS13 provide the opportunity in further research to establish a connection between the direct vicinity of the black hole and regions several light years away. Dr Michal Zajaček, second author of the study and scientist at Masaryk University in Brno (Czech Republic), added: “The star cluster IRS13 seems to be the key to unravelling the origin of the dense star population at the centre of our galaxy. We have gathered extensive evidence that very young stars within the range of the supermassive black hole may have formed in star clusters such as IRS13. This is also the first time we have been able to identify star populations of different ages – hot main sequence stars and young emerging stars – in the cluster so close to the centre of the Milky Way.”
Media Contact: Dr Florian Peißker Institute of Astrophysics +49 221 470 3491 peisskerph1.uni-koeln.de
Wanderung durch die Vulkaneifel, 17. September 2023 in Schalkenmehren
Die Wanderung führte durch die malerische Vulkaneifel in Rheinland-Pfalz um den Blick auf unsere Erde mit dem Blick ins Universum zu kombinieren. 40 Wanderfreunde waren begeistert, auf einem entspannten Weg zum Observatorium “Hoher List” etwas über die Entstehung der Erde und anderer Planeten zu erfahren. Die Tour führte entlang der HeimatSpur-Route MaareGlück bis zum Observatorium Hoher List. Anhand verschiedener Stationen gab es für die Teilnehmenden Einblicke in die Entstehung der Erde und die Entwicklung ihrer vulkanischen Aktivität. Dabei ging es auch um die Frage, was unseren Heimatplaneten so besonders macht. Im Observatorium erfuhren die Teilnehmenden zudem, wie wir fremde Planeten erforschen können.
Die Veranstaltung fand in Kooperation mit der Astronomischen Vereinigung Vulkaneifel am Hohen List e.V., Astronomers For Planet Earth und dem Natur- und Geopark Vulkaneifel GmbH statt.
Der Hiker’s Guide through the Galaxy fand im Rahmen des Wissenschaftsjahres 2023 – Unser Universum statt und wurde vom Bundesministerium für Bildung und Forschung gefördert.
To create a family friendly environment the Physics Department at the University of Cologne has set up a parent-child room supported by the German Research Foundation (DFG). The room offers a back-up option for combining work and child care in case of urgency, e. g. gaps in child care or in exceptional circumstances.
The University of Cologne has obtained a new Collaborative Research Center (CRC) from the German Research Foundation (DFG). In addition, two existing CRCs have been extended. The new CRC 1601 is entitled “The Cosmic Evolution of the Habitats of Massive Stars”. The CRC will be funded for four years. The spokesperson of the new Collaborative Research Center is astronomy professor Dr. Stefanie Walch-Gassner from the Institute of Astrophysics at the University of Cologne. The researchers are investigating the cosmic evolution of the habitats of massive stars – the gaseous environments in which these stars are born and with which they interact. Due to their short lifetimes and high energy output, massive stars have significantly influenced the evolution of galaxies since the beginning of the universe.
Within the CRC 1601, researchers are investigating the physical processes that determine the habitats of massive stars in different galactic environments. The new CRC combines four pillars: laboratory astrophysics, instrument development, observations, and theoretical modeling and simulations. The CRC partners have a strong profile as leading players in large international projects and have extensive experience in building and operating their own telescopes and developing state-of-the-art instruments in the infrared, submillimeter, and radio wave ranges. New developments, in particular the launch of the FYST/CCAT telescope in 2024, in which the Universities of Cologne and Bonn have a 25 percent stake, will be optimally supported by CRC 1601.
“We are extremely pleased about the new establishment of CRC 1601. The funding enables us to pursue an integrative approach. By combining the four pillars, we will be able to close major gaps in our understanding,” said Professor Dr. Walch-Gassner. “High-resolution studies of the habitats of massive stars will be combined with studies that look at the entire system ‘galaxy.’ This, and the inclusion of novel studies of the early universe and the associated extreme and highly variable conditions that prevail in young galaxies, will enable us to understand and quantify the cosmic evolution of the habitats of massive stars.”
![Clusters of young galaxies in the early Universe that later grow into large clusters are called protoclusters. This artist’s impression of the protocluster SPT2349-56 shows interacting galaxies of different shapes and sizes, and gas (orange) that is torn apart and heated by tidal forces. Due to its great distance from Earth, we see SPT2349-56 as it looked only 1.4 billion years after the Big Bang, when the Universe was 10% of its current age.] [Image Credit: N.Sulzenauer, MPIfR]](https://sfb1601.astro.uni-koeln.de/wp-content/uploads/2026/02/1920-1080-max-950x320.png)
![Clusters of young galaxies in the early Universe that later grow into large clusters are called protoclusters. This artist’s impression of the protocluster SPT2349-56 shows interacting galaxies of different shapes and sizes, and gas (orange) that is torn apart and heated by tidal forces. Due to its great distance from Earth, we see SPT2349-56 as it looked only 1.4 billion years after the Big Bang, when the Universe was 10% of its current age. [Image Credit: N.Sulzenauer, MPIfR]](https://sfb1601.astro.uni-koeln.de/wp-content/uploads/2026/02/1920-1080-max-1024x576.png)
![This radio image of the protocluster SPT2349-56 shows the intensity of ionized carbon (CII) emitted at a wavelength of 158 micrometers. Star symbols mark the centers of galaxies, while orange contours highlight the tidal arms around the inner region. These tidally ejected, galaxy-scale gas clumps are found to be ten times brighter than expected. The size of the Milky Way disk is shown at the same scale. [Image Credit: N.Sulzenauer, MPIfR]](https://sfb1601.astro.uni-koeln.de/wp-content/uploads/2026/02/1480-1384-max-1024x958.jpg)
