Astronomers have found the strongest evidence yet that Betelgeuse, one of the brightest and most famous stars in the night sky, is not alone.
After nearly a century of searching, researchers have captured the clearest image ever of a smaller companion star orbiting the giant red supergiant.
The discovery, published in Astronomy & Astrophysics, was made using the European Southern Observatory’s Very Large Telescope (VLT) in Chile. The research was led by astronomer Miguel Montargès from the Observatoire de Paris-PSL in France.
Betelgeuse is located in the constellation Orion and can easily be seen with the naked eye. The star has fascinated people for thousands of years because of its bright reddish color and its changing brightness.
Although it is one of the most carefully studied stars in the sky, it has continued to surprise scientists.
“We have shown that Betelgeuse is not single,” Montargès said. “It is accompanied by a faint stellar companion.”
Astronomers first suggested that Betelgeuse might have a companion star about 100 years ago. One reason for this idea was that a nearby star could help explain some of Betelgeuse’s unusual changes in brightness. However, despite many attempts using increasingly powerful telescopes, no one had been able to clearly detect the companion.
The breakthrough came after two studies published in 2024 predicted that the companion would be easiest to spot in December 2024, when it would be at its greatest distance from Betelgeuse in its orbit. Montargès and his team quickly arranged observations using the VLT and then spent several months carefully processing the images.
The results exceeded their expectations.
The newly detected companion, known as Betelgeuse B, appears to be much larger than scientists had predicted. Earlier estimates suggested it was about the same mass as our sun, but the new observations indicate it has roughly two to three times the sun’s mass.
The researchers directly detected light coming from the companion itself using the VLT’s powerful SPHERE instrument. This makes the new observation the clearest and strongest evidence so far that Betelgeuse truly has a companion. While earlier observations hinted that the star might exist, none provided such convincing proof.
Even so, the team wants to confirm the discovery by observing the companion again after it moves to the opposite side of Betelgeuse in its orbit. According to the researchers, however, there is now very little room for doubt.
The discovery also raises new questions about the future of Betelgeuse. As a red supergiant, the star is expected to end its life in a spectacular supernova explosion sometime in the distant future. In 2019 and 2020, Betelgeuse attracted worldwide attention when it suddenly became much dimmer, leading some people to wonder if the explosion was about to happen. Later studies showed that the fading was caused by a giant cloud of dust blocking some of the star’s light.
Now astronomers are eager to learn whether the newly discovered companion could influence Betelgeuse’s future evolution or even affect how it eventually explodes. While the answer remains unknown, the discovery opens an exciting new chapter in the study of one of the sky’s most famous stars.
Source: ESO.
