After centuries of speculation, astronomers have finally confirmed that Betelgeuse, the red supergiant star that humans have watched blazing in Orion’s shoulder for millennia, is not alone.
Astronomers have now confirmed that Betelgeuse has a companion star, a discovery made by NASA scientists using the International Gemini Observatory’s Gemini North telescope, as detailed in a newly published paper.
Betelgeuse is a relatively young star—at just ten million years old compared to our Sun’s 4.6 billion years—and with a radius 700 times that of the Sun, it’s also enormous. Located in the Orion constellation, Betelgeuse has long fascinated astronomers due to its shifting brightness, which follows two major cycles: one lasting roughly 400 days and another spanning about six years.
New Interest in Betelgeuse
“The Great Dimming,” an event in which the bright star experienced a sudden reduction in brilliance, was eventually discovered to be the result of a dust ejection, leading to renewed interest in the star. With a new round of focus, astronomers proposed a companion star as the most likely explanation for the red supergiant’s six-year variance cycle. Yet when researchers turned to the Hubble Space Telescope and the Chandra X-Ray Observatory to attempt viewing the theoretical companion, they observed nothing.
Steve Howell of NASA’s Ames Research Center led a team in finally detecting Betelgeuse’s proposed companion. The instrument that finally located the object was the Alopeke speckle imager, named for the Hawaiian word for fox, mounted on the Gemini North telescope.
Alopeke’s speckle imaging technique eliminates distortions created by the Earth’s atmosphere by utilizing very short exposure times. Removing these distortions pushes the imagery toward higher resolutions, with image clarity further bolstered by Gemini North’s 8.1-meter mirror’s immense light-collecting capabilities. Working in tandem, those abilities provided astronomers with the precision required to view the faint companion for the first time.
Determining Star Properties
Howell’s team studied the star’s light signature to better understand the newly identified object. In visible light, it is six orders of magnitude fainter than Betelgeuse. The companion is also significantly smaller, with a mass just 1.5 times that of the Sun. It appears to be a hot, blue-white pre-main-sequence star—classified as either A- or B-type—that has not yet begun burning hydrogen in its core.
Its orbit is just as remarkable. The companion is the first close-in stellar partner ever detected orbiting a supergiant star, located only about four times the Earth-Sun distance from Betelgeuse. What’s more, it orbits within Betelgeuse’s extended outer atmosphere, helping explain why it had remained undetected until now.
“Gemini North’s ability to obtain high angular resolutions and sharp contrasts allowed the companion of Betelgeuse to be directly detected,” said Howell. “Papers that predicted Betelgeuse’s companion believed that no one would likely ever be able to image it.”
Although both stars likely formed at the same time, scientists believe that tidal forces will eventually pull the smaller star into Betelgeuse, where it will be absorbed—likely within the next 10,000 years.
New Methods for Studying Red Supergiants
The research team hopes their findings will serve as a foundation for investigating other red supergiant stars with similar years-long brightness fluctuations.
“This detection was at the very extremes of what can be accomplished with Gemini in terms of high-angular resolution imaging, and it worked. This now opens the door for other observational pursuits of a similar nature,” Howell said.
“The speckle capabilities provided by the International Gemini Observatory continue to be a spectacular tool, open to all astronomers for a wide range of astronomy applications,” commented Gemini’s NSF program director Martin Still. “Delivering the solution to the Betelgeuse problem that has stood for hundreds of years will stand as an evocative highlight achievement.”
Looking ahead, Howell’s team plans to observe the companion again in November 2027, when it reaches its furthest separation from Betelgeuse, offering a clearer view.
The paper “Probable Direct Imaging Discovery of the Stellar Companion to Betelgeuse” appeared on July 24, 2025, in The Astrophysical Journal Letters.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.