An international team of astronomers, using the European Southern Observatory's Very Large Telescope (VLT) in Chile, has obtained the most convincing evidence to date that Betelgeuse, one of the brightest and most-watched stars in the night sky, is not alone. Deep inside its glare, the team involving Dr. Emma Bordier from the University of Cologne’s Institute for Astrophysics detected a faint point of light they call Betelgeuse B, a candidate companion star, at a high confidence level. The study was led by Dr. Miguel Montargès (LIRA, Observatoire de Paris) and involved researchers from institutions across France, the Netherlands, Chile, USA, Belgium and Germany.
Directly imaging a companion around a red supergiant has been a long-standing challenge. For decades, scientists had speculated that Betelgeuse might have a stellar companion, but every search had come back empty-handed or ambiguous. This new result is the strongest direct evidence yet that Betelgeuse has been sharing its life with a much smaller star all along, one whose light had simply been too faint to pick out from the giant star's glare until now.
Betelgeuse (Alpha Ori) is the bright reddish star marking the shoulder of the constellation Orion, visible to the naked eye from almost anywhere on Earth. It is a red supergiant nearing the end of its life, so enormous that if it sat where our Sun does, its surface would swallow the orbits of Mercury, Venus, Mars, and reach out toward Jupiter. It made global headlines in 2019–2020 when it suddenly lost much of its brightness, the so-called "Great Dimming", sparking speculation that it might be about to explode as a supernova. It turned out to be a cloud of dust the star had ejected, temporarily veiling it from view.
“Spotting a small companion star next to Betelgeuse is a bit like trying to photograph a firefly sitting right next to a lighthouse. Betelgeuse's brightness completely overwhelms the faint signal”, says Dr. Emma Bordier, co-author of the study, who helped design the observing strategy that made the detection possible. But the team managed to image Betelgeuse directly, meaning to detect the light from the star itself, using the SPHERE instrument on the ESO’s Very Large Telescope in Chile’s Atacama Desert, by combining a series of extremely sharp images with advanced image-processing techniques to reveal the faint companion hidden in the giant star's glare.
They observed Betelgeuse on the nights of 3 and 6 December 2024, chosen because earlier work, reinterpreting years of brightness variations, had predicted this was when the hypothetical companion would appear furthest from the star as seen from Earth, and therefore be easiest to spot.
The team discovered that Betelgeuse B is a young star which is more massive than predicted. Originally thought to be as massive as the Sun, the new observations reveal that Betelgeuse B has instead around two to three times the mass of the Sun.
To formally prove it is gravitationally bound to Betelgeuse, rather than a lucky unrelated star that happens to sit along the same line of sight, astronomers will need to observe it again on the opposite side of its orbit likely next year.
The minimum orbital period the team derives for the pair, at least 5.5 to 5.9 years, lines up well with a long-known but poorly understood roughly six-year cycle in Betelgeuse's brightness, its "long secondary period". This raises the possibility that the star's slow pulse of dimming and brightening every six years is, at least in part, the signature of this companion tracing its orbit, a question the team hopes to settle with follow-up observations.
The potential detection of Betelgeuse B will also prompt astronomers to investigate how the companion could affect Betelgeuse’s anticipated supernova explosion. “What we need to find out is whether this companion is going to have an impact on the evolution of the red supergiant”, says study leader Dr. Miguel Montargès.
The European Southern Observatory (ESO) is an intergovernmental research organization made up of 16 member states for ground-based astronomy. Its observatories are located in northern Chile.
Media contact:
Emma Bordier
Institute for Astrophysics
bordier(at)ph1.uni-koeln(dot)de
Press and Communications Team:
Anne Meyer
+49 221 470 3107
a.meyer(at)verw.uni-koeln(dot)de
Publication:
https://www.aanda.org/articles/aa/full_html/2026/07/aa61023-26/aa61023-26.html