Astronomers using ESO’s Very Large Telescope (VLT) have obtained the strongest evidence yet that Betelgeuse, the famous red supergiant in Orion, may be orbiting a faint companion star known as Betelgeuse B.
This VLT/SPHERE image provides the clearest view yet of the likely companion star Betelgeuse B. Image credit: ESO / Montargès et al.
Betelgeuse, also called Alpha Orionis or Alpha Ori, is the second-brightest star in the constellation Orion. The red supergiant is approximately 8 million years old and lies about 724 light-years from Earth.
With an estimated radius around 1,400 times larger than the Sun’s, Betelgeuse ranks among the largest known stars. It is also extraordinarily luminous, radiating more than 100,000 times the energy produced by the Sun.
Betelgeuse is approaching the final stages of its stellar evolution. When it eventually explodes as a supernova, the event is expected to become bright enough to remain visible in daylight for weeks.
“We have shown that Betelgeuse is not single; it is accompanied by a faint stellar companion,” said Dr. Miguel Montargès, an astronomer at the Observatoire de Paris.
Dr. Montargès and his colleagues detected a faint point of light close to Betelgeuse using SPHERE-ZIMPOL, an extreme adaptive-optics instrument designed for high-contrast astronomical imaging.
The observations were conducted on December 3 and 6, 2024. The dates were selected to coincide with the predicted maximum separation between Betelgeuse and the suspected companion, provisionally named Betelgeuse B.
“It is remarkable to see how SPHERE and advanced post-processing techniques, originally developed to detect exoplanets, can also reveal a companion orbiting a massive, evolved star such as Betelgeuse,” said Dr. Anthony Boccaletti, an astronomer at the Observatoire de Paris.
“To confirm that the companion is truly associated with Betelgeuse, we still need to observe it again in one year, when it should appear on the opposite side of the star. However, there is very little room left for doubt,” Dr. Montargès added.
The newly detected source was located approximately 52 milliarcseconds from Betelgeuse, corresponding to a projected separation of about 8.8 astronomical units (AU).
This distance is consistent with earlier orbital models, which estimated that Betelgeuse B completes an orbit around the red supergiant every 5.5 to 6 years.
Based on the observations, the researchers estimate that Betelgeuse B is a young star with a mass between 2.6 and 3.1 times that of the Sun.
The absence of hydrogen-alpha emission, ultraviolet radiation, and X-rays supports the interpretation that Betelgeuse B is a relatively ordinary young main-sequence star rather than a highly active protostar.
“Honestly, I thought we would not have enough sensitivity to detect Betelgeuse B at the position predicted by the models. Because the companion is more massive than expected, we were able to see it,” Dr. Montargès said.
“The discovery of a nearby companion that is more massive and brighter than the Sun around such a well-studied star is remarkable,” he added.
“These are among the best moments in science: seeing something new and unexpected.”
The team’s findings have been published in the journal Astronomy & Astrophysics.
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M. Montargès et al. 2026. VLT/SPHERE images of the candidate companion of Betelgeuse. A&A 711, L12; doi: 10.1051/0004-6361/202661023
Source: www.sci.news