Astronomers capture clearest image yet of Betelgeuse’s companion star

A team of astronomers has obtained the most definitive image to date of a star orbiting Betelgeuse, the red supergiant visible to the naked eye in the constellation Orion, ending what the lead researcher called "a century-long quest."

A Hidden Companion Revealed

Using the SPHERE instrument on the European Southern Observatory's Very Large Telescope in Chile's Atacama Desert, a team led by Miguel Montargès of the Observatoire de Paris-PSL directly imaged the companion, known as Betelgeuse B and previously named Siwarha. The results, published Monday in Astronomy & Astrophysics, show the companion is two to three times the mass of the sun — far heavier than earlier estimates of roughly one solar mass.phys+2

"We have shown that Betelgeuse is not single, it is accompanied by a faint stellar companion," Montargès said. "I jumped from my chair when I saw the processed images."phys

Decades of Prediction, Months of Processing

Betelgeuse's brightness has been known to fluctuate for millennia, and for about a century astronomers hypothesized a companion star could be responsible. Two studies published in 2024 predicted that December of that year would offer the best window for detection, when the companion would appear farthest from its host star as seen from Earth.phys

Montargès and his team observed Betelgeuse with the VLT in December 2024 and spent months processing the data. "Honestly, I thought we did not have the sensitivity to detect Betelgeuse B as it was predicted," he said. "Because it is more massive than predicted, we see it!"phys

Andrea Dupree, an astronomer at the Center for Astrophysics | Harvard & Smithsonian and a study coauthor, called the result a "gorgeous detection." "I mean, it's really there!" she saidscientificamerican.

What Comes Next

While earlier evidence for the companion included a possible detection with the Gemini North Telescope in Hawaii and observations from NASA's Hubble Space Telescope that revealed the companion's gravitational wake through Betelgeuse's outer atmosphere, the new SPHERE imaging represents the strongest direct evidence yet.space+1

The team noted that full confirmation will require observing the companion on the opposite side of the star within the next year. The discovery also raises new questions about whether Betelgeuse B could influence the red supergiant's eventual death in a supernova explosion. "The question is truly open whether this companion is going to have an impact on the evolution of the red supergiant," Montargès said.phys