Astronomers using the European Southern Observatory's Very Large Telescope in Chile have obtained the clearest image yet of a likely companion to Betelgeuse, the famous red supergiant in Orion. The team reported on July 28 that its direct detection provides strong evidence that the closely studied star is not alone, while stressing that another observing epoch is required to prove the two objects are gravitationally bound.
The candidate, called Betelgeuse B, appeared in data collected with the VLT's SPHERE instrument on December 6, 2024, when earlier models predicted that a companion would be near its widest apparent separation from Betelgeuse. Researchers spent months processing the observations with two independent techniques designed to distinguish a faint point source from the glare and complex surface of the supergiant.
The peer-reviewed study in Astronomy & Astrophysics reports a detection significance of 6.1 sigma with its main analysis and 5.1 sigma with a second method. The source lay 52.32 milliarcseconds from Betelgeuse in the image. Assuming both stars formed together, its brightness is consistent with a young main-sequence star about 2.6 to 3.1 times the mass of the Sun, rather than the roughly solar-mass companion initially expected.
Astronomers have searched for an explanation of Betelgeuse's long brightness cycle for about a century. Studies published in 2024 linked the roughly 2,200-day cycle to a possible orbit and predicted the favorable December 2024 viewing geometry. A Gemini North observation previously offered a tentative 1.5-sigma signal, while ultraviolet and X-ray searches did not detect the object; the new visible-light result is substantially stronger and agrees with the predicted position.
The finding matters beyond one familiar star because companions around red supergiants are difficult to see and can influence stellar winds, surface structure and evolution before a supernova. The paper estimates a projected separation of at least about 8.8 astronomical units and an orbital period of at least roughly six years under one distance estimate, broadly matching Betelgeuse's long brightness variation. It remains unclear whether the candidate will affect the supergiant's eventual explosion.
The researchers plan to look for Betelgeuse B on the other side of the primary star after it advances in its proposed orbit. That follow-up would test whether the source moves with Betelgeuse and formally confirm it as a companion rather than a chance alignment. Additional observations would then refine the orbit and help determine whether long brightness cycles can reveal hidden partners around other red supergiants.
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