Astronomers have captured the most definitive images yet of a companion star orbiting Betelgeuse, the iconic red supergiant that marks one shoulder of the constellation Orion. The smaller star, formally named Siwarha, was detected using exoplanet-hunting imaging techniques on the Very Large Telescope in Chile and will be described in a forthcoming paper in Astronomy & Astrophysics.
The detection caps more than a century of speculation about whether Betelgeuse travels alone. Researchers had previously linked a mysterious six-year brightness cycle to an unseen companion, but earlier attempts to photograph it were inconclusive. The new images, taken in December 2024 when the companion was predicted to reach its farthest apparent separation from Betelgeuse, finally put a face to the long-suspected buddy.
Exoplanet Tricks Reveal a Dim Neighbor
Spotting a companion next to Betelgeuse is not unlike photographing a firefly perched on a searchlight. The red supergiant is enormous and luminous, while Siwarha is comparatively dim. To overcome that contrast, the team borrowed imaging methods originally developed to find exoplanets orbiting bright host stars — techniques that suppress the blinding central light to reveal fainter objects nearby.
Andrea Dupree of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and her colleagues used the SPHERE instrument on the Very Large Telescope to observe Betelgeuse on two days in December 2024. Dupree was visiting colleague Miguel Montargès, an astronomer at the Paris Observatory, when he finished processing the data.
“He ran in and said, ‘Oh my god, look! Look what I just found!'” Dupree recalls.
A Name Tied to Orion’s Mythology
The companion already carries a formal name: Siwarha, meaning “her bracelet,” a nod to Betelgeuse’s own Arabic name, which translates roughly to “hand of the giant.” The naming ties the smaller star to the mythology and etymology that have long surrounded one of the most recognizable stars in the night sky.
“It’s really an iconic star,” Dupree says of Betelgeuse itself, which has fascinated observers for generations — not least because its brightness varies on a complex schedule. Some of those variations, occurring every few hundred days, are attributed to pulsations inside the star. But a longer variation, lasting roughly six years, remained puzzling until 2024, when astronomers connected it to a smaller star orbiting Betelgeuse.
A Heftier Companion Than Expected
Assuming the two stars formed together, Siwarha has a mass between 2.6 and 3.1 times that of the sun, Dupree says. That is more massive than astronomers originally expected, and it shapes how researchers will model the system’s history and the gravitational dance between the two stars.
The mass estimate carries implications beyond mere bookkeeping. A more massive companion exerts a stronger gravitational influence on Betelgeuse and on the surrounding dust and gas, which could help explain the red supergiant’s long-period brightness variations and refine models of how massive stars evolve in binary systems.
What Happens Next
Montargès plans to observe Betelgeuse again in late 2027, when Siwarha is expected to appear on the opposite side of the supergiant as seen from Earth. Catching the companion on the other side of its orbit would provide the clinching evidence that the detection is real and not an artifact of dust or background light.
Dupree is already leaning toward conviction, even as her colleague remains cautious. “Miguel, he’s very conservative. He keeps calling it a candidate,” she says. “But some of us are more uninhibited. We say it’s really there.”
For astronomers studying stellar evolution, the Betelgeuse-Siwarha system offers a rare laboratory: a nearby, well-studied supergiant with a companion whose orbit can be mapped directly. Future observations could pin down the companion’s precise mass, orbit, and age, and help settle whether Betelgeuse’s famous dimming events — including its dramatic 2019 fade — involve interactions with Siwarha or are driven entirely by the supergiant’s own internal physics.
— Priya Nair, science desk, AXO News