Astronomers Capture Clearest Image Yet of Betelgeuse's Hidden Companion

Astronomers have their strongest evidence yet that Betelgeuse, the well-known red supergiant star in the Orion constellation, has a hidden stellar companion. A team led by French astronomer Miguel Montargès used the European Southern Observatory's (ESO) Very Large Telescope (VLT) to capture the clearest image yet of what is believed to be Betelgeuse B, a star orbiting the red giant. The study was published today in the journal Astronomy & Astrophysics.

The idea that Betelgeuse might have a companion was first raised about a century ago to explain some of the star's brightness changes, but decades of observations failed to detect it clearly. Two studies published in 2024 predicted the companion would reach its greatest apparent separation from Betelgeuse in December 2024, giving astronomers their best chance to see it. Montargès and colleagues observed the star with the VLT that month, then spent several months processing the data.

The team directly imaged Betelgeuse B, detecting light from the companion itself, using the VLT's SPHERE instrument in Chile's Atacama Desert. Earlier observations, including a possible direct detection with the Gemini North Telescope in Hawaii, USA, had hinted the companion existed, but the new VLT images are the strongest evidence so far. Scientists had first estimated the companion's mass was close to the Sun's; the new observations suggest it is considerably larger, about two to three times the Sun's mass.

The case is not fully closed. Astronomers want to observe the candidate companion again in about a year, when its orbit predicts it should appear on the other side of Betelgeuse, before they are certain. Betelgeuse drew worldwide attention several years ago when its brightness noticeably dropped, briefly fueling speculation it was nearing its eventual supernova; Montargès's team later found the dimming was instead caused by a cloud of dust blocking its light. Researchers now plan to study whether Betelgeuse B could influence the red supergiant's future evolution, including that eventual supernova.