Betelgeuse, the red supergiant marking Orion’s shoulder, has long been suspected, but never confirmed, to host a stellar companion. Using the extreme adaptive-optics instrument SPHERE, in its ZIMPOL imaging mode, on ESO’s Very Large Telescope, we have now directly detected a companion star that is about 1,000 times fainter than Betelgeuse, partly explaining why it had remained hidden until now.

We observed Betelgeuse on 3 and 6 December 2024, timed to the predicted maximum apparent separation of a hypothetical companion inferred from a reinterpretation of the star’s ~2200-day “long secondary period” (LSP) brightness cycle. Processing the angular and spectral differential imaging data with the PACO ASDI algorithm, we detected a point source in the continuum-Hα filter at 6.1σ, independently recovered at ~5σ with principal component analysis. The source sits at a separation of 52.32 ± 0.18 mas and position angle 117.12 ± 0.60°, corresponding to a projected distance of ~8.8 au at the asteroseismic distance of 168 pc, comparable to Saturn’s orbit around the Sun, and implying a minimum orbital period of 5.5–5.9 years, consistent with the LSP. 

Fitting the source’s continuum flux against pre-main-sequence PHOENIX model atmospheres, and assuming coevality with the 8–10.5 Myr-old Betelgeuse A, favours a 2.6–3.1 M⊙ star of spectral type B8.5V–B9.5V that has just reached the main sequence. Non-detection in narrow-Hα, together with the absence of UV and X-ray signatures reported elsewhere, disfavours a pre-main-sequence interpretation.

These results corroborate a tentative 1.5σ detection reported by Howell et al. 2025 (using Gemini North Telescope in Hawaiʻi), and strengthen the case that Betelgeuse’s LSP traces orbital motion rather than pulsation alone; estimates of dust sublimation around the companion suggest this mechanism alone cannot account for the full LSP amplitude, favouring a dynamical origin instead. Confirming Betelgeuse B as gravitationally bound, rather than a chance alignment, will require a second astrometric epoch near opposite orbital phase, motivating continued high-contrast monitoring of this benchmark red supergiant.

This teamwork was led by Miguel Montargès (LIRA, Observatoire de Paris), with Emma Bordier (SFB 1601) among the co-authors; it is published in Astronomy & Astrophysics (https://www.aanda.org/articles/aa/full_html/2026/07/aa61023-26/aa61023-26.html), and was the subject of press releases from ESO (https://www.eso.org/public/news/eso2611/) and the University of Cologne (https://uni-koeln.de/en/university/news/news/news-detail/beteigeuze-hat-einen-partnerstern-astronominnen-liefern-den-bislang-ueberzeugendsten-beweis).