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Visual proof: Betelgeuse does have a companion star

28 July 2026

An international team led by an astronomer from Paris Observatory – PSL, involving scientists from the CNRS, Université Grenoble Alpes and the Côte d’Azur Observatory, provides the most convincing evidence to date that Betelgeuse is not a solitary star. Using observations from the European Southern Observatory’s (ESO) Very Large Telescope (VLT), the researchers obtained the most significant image ever acquired of its companion star, putting an end to nearly a century of questioning. The findings are published on 28 July 2026 in the journal Astronomy & Astrophysics.

VLT images of Betelgeuse and its companion
Using ESO’s Very Large Telescope (VLT), astronomers have obtained the clearest image ever of what likely is Betelgeuse B, a star orbiting Betelgeuse.
Betelgeuse is a red supergiant star in the Orion constellation. Its brightness changes periodically, and for decades astronomers had suspected that some of these variations could be due to a companion star orbiting around it.
The image in the middle inset in this image was taken in January 2019 with the SPHERE instrument at ESO’s VLT, and shows Betelgeuse itself. The image in the inset on the left was taken in December 2024, when the companion was predicted to be furthest apart from Betelgeuse as seen from Earth. In this inset Betelgeuse has been removed, revealing a source (marked with a crosshair) consistent with being Betelgeuse B.
Credit: ESO/M. Montargès et al. Background: N. Rissinger (skysurvey.org)

Visible to the naked eye in the constellation of Orion, Betelgeuse has fascinated observers since Antiquity. This red supergiant, whose mass is estimated at between 15 and 20 times that of the Sun and whose radius reaches nearly 700 to 1,000 solar radii, ranks among the most imposing stars in our galactic neighbourhood. Known for its variations in brightness, it continues to deliver new surprises.

Two studies published in 2024 and 2025 suggested that some of these variations could be explained by the presence of a companion star. They had even predicted that by the end of 2024, this second star would be in an orbital position particularly favourable for its detection. Observations carried out in December 2024 with the ESO’s VLT made it possible to put this hypothesis to the test.

"This is the culmination of a century-long quest," says Miguel Montargès, deputy astronomer at Paris Observatory – PSL and lead author of the study. "We have shown that Betelgeuse is not alone, it is accompanied by a very discreet companion."

An observational feat

The image was obtained using SPHERE, the high-contrast imaging instrument installed on ESO’s VLT in Chile. The challenge was considerable. Betelgeuse is tens of thousands of times brighter than its suspected companion. Directly detecting the light of this star, drowned out by the glare of the supergiant, required several months of data processing and analysis. "It is remarkable to see how well SPHERE and advanced post-processing techniques, originally developed to detect exoplanets, also excel at detecting a companion around a massive, evolved star like Betelgeuse," states Anthony Boccaletti, CNRS research director and co-author of the study.

A hypothesis now solidly supported

The presence of a companion star had already been suggested several times over the past decades, and an observation made with the Gemini North telescope had provided an encouraging clue. The new observations, however, constitute the strongest evidence obtained to date, thanks to a direct image of the companion with a significant detection.

The researchers estimate that this star orbits Betelgeuse roughly every six years, consistent with models proposed in recent years. A new observation campaign will nonetheless make it possible to track its orbital motion and definitively confirm this interpretation.

"To be certain the companion is really there, we still need to observe it in a year’s time on the other side of the star, but there is now hardly any room left for doubt," adds Miguel Montargès.

Better understanding the final stages of massive stars

Betelgeuse caused a stir in 2019-2020 when its brightness suddenly dimmed, fuelling speculation about an imminent supernova explosion. A study led by Miguel Montargès and his collaborators later showed that this spectacular dimming resulted from the ejection of a large dust cloud that temporarily obscured the star.

The discovery of its companion now opens up a new avenue of research. Gravitational interactions between the two stars could influence the mass loss of Betelgeuse, and even alter certain aspects of its final evolution before it explodes as a supernova.

Reference

This work is the subject of a paper titled "VLT/SPHERE imaging of the candidate companion of Betelgeuse," by M. Montargès, A. Boccaletti et al., published in the journal Astronomy & Astrophysics on 28 July 2026.
DOI: 10.1051/0004-6361/202661023
URL: https://www.aanda.org/10.1051/0004-6361/202661023

Illustrations

VLT image of Betelgeuse’s companion
This image, taken with ESO’s Very Large Telescope (VLT), shows the clearest image ever of what likely is Betelgeuse B, a star orbiting Betelgeuse. The image was taken with the SPHERE instrument in December 2024, when the companion was predicted to be furthest apart from Betelgeuse as seen from Earth. The circle indicates the size of Betelgeuse, which has been removed. The bright source to the left, marked with a crosshair, is consistent with being Betelgeuse B.
Credit: ESO/M. Montargès et al.

Additional resources

ESO press release: «Astronomers find strongest evidence yet that Betelgeuse has a companion»
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Scientific contacts

  • Miguel Montargès
    Deputy astronomer at Paris Observatory - PSL (LIRA)
    +33 1 45 07 76 95
  • Anthony Boccaletti
    CNRS research director at Paris Observatory - PSL (LIRA)
    +33 1 45 07 77 21

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