Astronomers have captured the clearest image yet of a faint companion star long suspected to orbit Betelgeuse, the red supergiant whose unpredictable dimming has puzzled skywatchers for more than a century. The observations, made with the European Southern Observatory's Very Large Telescope in Chile, offer what researchers call the strongest evidence so far that Betelgeuse is not alone.
A team led by Miguel Montargès of the Observatoire de Paris used the VLT's SPHERE-ZIMPOL instrument — an extreme adaptive-optics system built to detect faint exoplanets — to pick out a point of light near Betelgeuse on December 3 and 6, 2024, timed to coincide with the moment models predicted the companion, dubbed Betelgeuse B, would sit farthest from its parent star as seen from Earth. At that separation, roughly 52 milliarcseconds, or about 8.8 astronomical units, the companion was faint enough to have escaped detection in previous searches.
What surprised the team was its mass: between 2.6 and 3.1 times that of the Sun, well above the roughly one-solar-mass companion earlier models had predicted.
Because it is more massive than predicted, we see it. I jumped from my chair when I saw the processed images.
Miguel Montargès, Observatoire de Paris
Betelgeuse, located about 724 light-years away in the constellation Orion, is one of the largest stars known, with a radius roughly 1,400 times the Sun's. Astronomers first proposed a hidden companion nearly a hundred years ago to explain the star's irregular brightness swings, and two independent studies in 2024 predicted its orbital position with enough precision to make this month's window observable. The absence of hydrogen-alpha emission, ultraviolet light or X-rays from the object suggests it is an ordinary young main-sequence star rather than a more energetic protostar, with an estimated orbital period of five and a half to six years.
Co-author Anthony Boccaletti noted that the imaging technique's exoplanet-hunting origins proved unexpectedly well suited to the task of spotting a stellar companion against the glare of a supergiant. The team says confirmation will require observing Betelgeuse B again in roughly a year, once it swings to the opposite side of its orbit — a test Montargès says leaves "very little space left for doubt" about the discovery holding up. Researchers are also now examining whether the companion could influence Betelgeuse's evolution as it approaches its anticipated supernova explosion, an event some models suggest could become visible from Earth within the next 100,000 years.
