Astronomers Capture Clearest Evidence Yet of a Hidden Star Orbiting Betelgeuse

Astronomers have obtained their strongest evidence yet that Betelgeuse, the bright red supergiant star in the constellation Orion, is not alone. Using the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Chile, a team led by French astronomer Miguel Montargès of the Observatoire de Paris captured the clearest image so far of what is likely a companion star, now called Betelgeuse B. The findings are published in Astronomy & Astrophysics.

The possibility of a companion was first proposed about a century ago to explain some of Betelgeuse's brightness variations, but earlier searches found no convincing detection. Two studies published in 2024 predicted that the companion would reach its greatest apparent separation from Betelgeuse in December of that year, making it easier to pick out from the much brighter supergiant. Montargès and colleagues observed Betelgeuse during that window using an imaging instrument called SPHERE, then spent several months processing the data. "I jumped from my chair when I saw the processed images," Montargès said.

Earlier estimates had suggested the companion might have roughly the same mass as the Sun. The new observations instead indicate Betelgeuse B is about two to three times as massive as the Sun — bright and massive enough that the team could detect it directly, rather than only inferring its presence. "Because it is more massive than predicted, we see it," Montargès said. Researchers still need to observe the companion on the opposite side of its orbit, expected in about a year, before considering the discovery fully confirmed.

Betelgeuse drew wide attention several years ago when it dimmed noticeably, fueling speculation that its expected eventual supernova explosion might be near; Montargès and other astronomers later attributed that dimming to a temporary dust cloud rather than an imminent explosion. Researchers now plan to study whether Betelgeuse B could influence the star's evolution or its eventual supernova.