An image as proof? Betelgeuse may not be alone.
An international team has obtained the sharpest image to date of a star that appears to orbit the famous red supergiant. This observation provides the strongest clue after nearly a century of research.
Visible to the naked eye in the constellation Orion, Betelgeuse regularly varies in brightness. Astronomers have long suspected that a companion star could contribute to some of these variations. Two studies published in 2024 predicted it would be easier to distinguish in December of that year, when it would appear farthest from Betelgeuse.
VLT images of Betelgeuse and its potential companion
The researchers therefore observed the system on that date with the Very Large Telescope of the European Southern Observatory in Chile. They used SPHERE, an instrument designed in particular to separate the faint light of exoplanets from the glare of their star. Several months of processing were then needed to bring out the sought-after signal.
The image obtained directly shows the light of the candidate, provisionally called Betelgeuse B. The new data indicate a mass between two and three times that of the Sun, higher than initial predictions, which imagined it close to one solar mass. This difference explains why SPHERE was able to detect it despite the dominant glare of the supergiant.
Other clues had already supported the existence of a companion, including a possible detection with the Gemini North telescope. However, the new image is presented by the team as the most convincing observational evidence. The authors remain cautious: they still speak of a candidate star, because an isolated bright point is not enough to establish its orbital motion.
An observation about a year later is expected to provide the decisive test. If the object is then found on the other side of Betelgeuse, at the position predicted by its orbit, its association with the system will become much harder to dispute. This check will also make it possible to better determine its trajectory and physical properties.
The discovery could alter the models describing the evolution of Betelgeuse. This massive, aged star will soon end by exploding as a supernova.
A sufficiently massive companion can exchange matter or disturb the outer layers of a supergiant over time. Astronomers will therefore need to determine whether Betelgeuse B already influences the variations of the main star and whether it will change its final evolution. The next image will first look for the expected orbital shift, an essential condition before going further.