Hubble Telescope spies ‘wake’ of supergiant Beutelgeuse’s hidden companion star
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This artist’s concept shows the red supergiant star Betelgeuse and an orbiting companion star. The companion, which rotates clockwise from this perspective, generates a dense wake of gas that extends outward. It is so close to Betelgeuse that it passes through the supergiant’s extended outer atmosphere. The companion star is not to scale; it would be a pinprick compared to Betelgeuse, which is hundreds of times larger. The distance from the companion to Betelgeuse is scaled relative to the diameter of Betelgeuse. | Credit: NASA, ESA, Elizabeth Wheatley (STScI); Sciences: Andrea Dupree (CfA)
Astronomers and scientists love Betelgeuse because it shines so brightly. While most stars appear as tiny points of light, Betelgeuse is large enough and close enough that we can study it in much more detail. But this red supergiant star is strange, often moving, dimming and brightening in our night sky.
In July 2025scientists have found a companion star in Betelgeusethe star’s outer atmosphere, which could explain the red supergiant star’s strange appearance. Now, using new observations of the Hubble Space TelescopeAlong with data from observatories here on Earth, scientists detected the wake of Betelgeuse’s companion star, named Siwarha. This new study confirms the existence of Siwarha.
“The idea that Betelgeuse has an undetected companion has gained popularity in recent years, but without direct proof it was an unproven theory,” said the study’s lead author, Andrea Dupree, an astronomer at the Center for Astrophysics | Harvard & Smithsonian (CfA), said in a statement from NASA on Monday (January 5).
“With this new direct evidence, Betelgeuse gives us a front-row seat to observe how a giant star evolves over time,” she added. “Finding the wake of its companion now allows us to understand how stars as it evolves, loses matter and ends up exploding as it supernovae“.
Using combined observations from Hubble and telescopes at the Fred Lawrence Whipple Observatory in Arizona and the Roque de Los Muchachos Observatory in the Canary Islands, researchers spotted a “pattern of changes” in Betelgeuse. They could recognize Siwarha’s wake or trail because it is made of denser material than the gases in the outer atmosphere surrounding it.
Scientists used NASA’s Hubble Space Telescope to search for evidence of a wake generated by a companion star orbiting Betelgeuse. The team discovered a noticeable difference in the light displayed in the left peak when the companion star was at different points in its orbit. | Credit: NASA, ESA, Elizabeth Wheatley (STScI); Sciences: Andrea Dupree (CfA)
Every six years, when Siwarha crosses Betelgeuse and Earththe wake becomes visible, and due to its density, it modifies the spectrum of colors emitted by the different elements of Betelgeuse’s atmosphere.
“It’s a bit like a boat moving on water. The companion star creates a ripple effect in Betelgeuse’s atmosphere that we can actually see in the data,” Dupree said. “For the first time, we observe direct signs of this wake, or gas trail, confirming that Betelgeuse actually has a hidden companion that shapes its appearance and behavior.”
Siwarha will become visible again in 2027 and researchers are already planning new observations for this event.
The new results on Siwarha’s wake were presented Monday at the 247th meeting of the American Astronomical Society in Phoenix, Arizona. The study will appear in The Astrophysical Journal.
