Recent multi-year observations from the NASA/ESA Hubble Space Telescope, along with data from the Fred Lawrence Whipple and Roque de los Muchachos Observatories, have unveiled how a faint companion star, identified as Siwalha, has carved a path through the vast atmosphere of Betelgeuse. These findings illuminate long-standing mysteries regarding stellar evolution and advance our understanding of large-scale stellar dynamics.
Artist’s concept depicting the red supergiant star Betelgeuse alongside its orbiting companion. Image credit: NASA/ESA/Elizabeth Wheatley, STScI/Andrea Dupree, CfA.
Betelgeuse, an impressive 8-million-year-old red supergiant star, is prominently situated on the shoulder of the Orion constellation, approximately 724 light-years away from Earth.
With a radius roughly 1,400 times that of the Sun, Betelgeuse stands as one of the largest known stars in the universe.
Commonly referred to as Alpha Orionis or Alpha Ori, Betelgeuse is not just renowned for its size but also for its brightness, radiating more light than 100,000 suns combined.
As Betelgeuse nears the end of its life cycle, its impending explosion is expected to be so luminous that it will be visible in daylight for several weeks.
Astronomers have been meticulously monitoring variations in Betelgeuse’s brightness and surface characteristics for decades to uncover the underlying causes of its behavior.
Interest peaked in 2020 when Betelgeuse seemed to exhibit unusual “sneezing” behavior, suddenly dimming unexpectedly.
Two key periods of fluctuations have intrigued scientists: a short 400-day cycle, likely linked to the star’s own pulsations, and a longer 2,100-day period that remains more elusive.
Researchers have theorized various explanations for these fluctuations, including large convective cells, dust clouds, magnetic activities, and the possible presence of hidden companion stars.
A recent comprehensive study suggests that the longer secondary period is best explained by a low-mass companion star that orbits deep within Betelgeuse’s atmosphere. While some scientists reported possible detections, solid evidence was previously lacking—until now.
For the first time, astronomers have gathered compelling evidence that a companion star is indeed influencing the supergiant star’s atmosphere.
Data changes in the spectra of stars—colors of light emitted by different elements—and shifts in the gas’s speed and direction in the outer atmosphere confirm the presence of denser material and wake effects.
This peculiar signature appears soon after the companion star transits in front of Betelgeuse approximately every six years, further endorsing the theoretical model.
Dr. Andrea Dupree, an astronomer at Harvard University & Smithsonian Center for Astrophysics, commented, “It’s akin to a boat sailing through water; the companion star induces a ripple in Betelgeuse’s atmosphere that is directly observable in the data.”
“For the first time, we are witnessing definitive signs of this wake or gas signature, validating that Betelgeuse does indeed harbor a hidden companion that influences its observable characteristics and behavior.”
The team’s research paper will soon be published in the Astrophysical Journal.
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Andrea K. Dupree et al. 2026. Betelgeuse: Expanding trail of the companion star detected. APJ in press. arXiv: 2601.00470
Source: www.sci.news
