An international team of astronomers has captured the clearest image yet of the elusive companion star orbiting the red supergiant Betelgeuse. This landmark observation, made using the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Chile, resolves a mystery that puzzled scientists for nearly a century. The discovery, detailed in a paper published on July 28, 2026, in the journal Astronomy & Astrophysics, reveals that Betelgeuse is not a solitary star but part of a binary system, with its companion now officially named Siwarha. This finding offers crucial insights into the life and eventual fate of massive stars like Betelgeuse.[space+4]
A Century of Speculation Ends
For decades, astronomers suspected Betelgeuse had a hidden companion. The bright star, visible to the naked eye in the constellation Orion, shows peculiar changes in its brightness over time. While some variations occur every 400 days due to pulsations within the star, a longer, six-year cycle remained a puzzle. Scientists first proposed a companion star around 100 years ago to explain these enigmatic dimmings.[noirlab+12]
Previous attempts to directly observe this companion were unsuccessful due to Betelgeuse's immense brightness and its own ejected material. The red supergiant is so large that if it replaced our Sun, its surface would extend past the orbit of Mars and even reach toward Jupiter. Its intense light obscured any nearby, fainter objects. The star also famously underwent a "Great Dimming" event between late 2019 and early 2020, sparking speculation it was about to explode. However, further research showed this dimming was caused by a large cloud of dust ejected from Betelgeuse's surface temporarily blocking its light. This event, and the star's inherent variability, made the search for a companion even more challenging.[universetoday+14]
Unveiling Siwarha
The recent breakthrough came from observations in December 2024, a time when astronomers predicted the companion star would be at its furthest separation from Betelgeuse as seen from Earth. This optimal viewing window allowed a team led by Miguel Montargès, an astronomer at the Paris Observatory – PSL, to use the VLT's SPHERE instrument. This instrument employs advanced techniques, originally developed to find exoplanets, to block out the glare of bright stars and reveal dimmer objects nearby.[universetoday+9]
"This is the conclusion of a century-long quest," said Montargès in a statement. Headded that he "jumped from his chair" upon seeing the processed images. The companion star, now officially dubbed Siwarha, meaning "her bracelet" in Arabic, was previously difficult to detect because it was fainter than its massive partner.[space+10]
The new observations reveal that Betelgeuse B, or Siwarha, is significantly more massive than earlier predictions. Scientists initially thought it was about 1.5 times the mass of our Sun. However, the VLT data shows it has a mass between two and three times that of the Sun. Siwarha is a hot, young, blue-white star, classified as an A- or B-type pre-main-sequence star, meaning it has not yet begun hydrogen burning in its core. Itshines with a luminosity up to 92 times that of the Sun. The two stars are gravitationally bound, orbiting each other at a distance roughly comparable to Saturn's orbit around our Sun. Another team led by Steve Howell of NASA Ames Research Center also made a probable direct detection of the companion in 2025 using the 'Alopeke instrument on Gemini North.[en+14]
Implications for Stellar Evolution
The confirmed presence of Siwarha fundamentally changes our understanding of Betelgeuse. Astronomers now believe the companion star plays a significant role in Betelgeuse's variable brightness, particularly the mysterious six-year cycle. Gravitational interactions between Betelgeuse and Siwarha could also influence how Betelgeuse loses mass, and potentially alter aspects of its final evolution before it explodes as a supernova.[noirlab+3]
Betelgeuse, located about 650 light-years from Earth, is a red supergiant nearing the end of its life, estimated to be around 10 million years old. Ithas a mass between 14 and 19 times that of the Sun and a radius up to 1,000 times larger. The discovery of its companion helps scientists better model the behavior of other red supergiant stars across the galaxy.[universetoday+13]
While the images provide the strongest evidence yet, further observations are planned to definitively confirm the companion's orbit and characteristics. Scientists hope to observe Siwarha again in late 2027 when it is expected to appear on the other side of Betelgeuse. Researchers also predict that strong tidal forces will eventually cause Siwarha to spiral into Betelgeuse, a dramatic event estimated to occur within the next 10,000 years. This discovery marks a pivotal moment in understanding one of the most famous stars in our night sky and the complex lives of massive stars.[noirlab+7]
