Betelgeuse and its newly discovered companion star in Orion as captured by the ‘Alopeke speckle imager mounted on the Gemini North Telescope. Credit: NSF NOIRLab

Key Takeaways: Using the Gemini North Telescope’s speckle imager, ‘Alopeke, astronomers directly imaged a previously hypothesized companion star to Betelgeuse, located approximately 4 AU from the red supergiant.

The companion star is estimated to be an A- or B-type pre-main sequence star with approximately 1.5 solar masses, significantly fainter than Betelgeuse in visible light.

The discovery offers a potential explanation for Betelgeuse’s six-year variability cycle, suggesting the companion’s influence on dust distribution within the red supergiant’s extended atmosphere.

This close binary system’s future involves the eventual consumption of the companion star by Betelgeuse within the next 10,000 years, potentially affecting Betelgeuse’s evolutionary timeline and supernova event.

On July 21, 2025, NSF NOIRLab issued a press release stating that astronomers had detected a long-anticipated companion star to the red supergiant Betelgeuse. The team of astrophysicists, led by Steve Howell, senior research scientist at NASA’s Ames Research Center, observed Betelgeuse’s companion using ‘Alopeke, a speckle imager mounted on the Gemini North Telescope located atop Maunakea in Hawai‘i.

An iconic star

Betelgeuse is one of the most iconic stars in the night sky, famed not only for its ruddy hue and position at Orion’s shoulder, but also for its turbulent and unpredictable nature. Located about 650 light-years away, the star is a true giant, spanning nearly 700 times the Sun’s radius. Though only 10 million years old, Betelgeuse is already nearing the end of its life. For millennia, human observers have watched it fluctuate in brightness. Astronomers have traced that variability to a 400-day pulsation cycle and a second, slower rhythm lasting about six years.

The Great Dimming

That longer cycle drew renewed attention in 2019 and 2020, when Betelgeuse unexpectedly dimmed so drastically that some believed its supernova might be imminent. The event, now known as the “Great Dimming,” was ultimately blamed on a veil of dust ejected by the star itself. But it also prompted astronomers to take a closer look at what might be lurking in Betelgeuse’s glow.

Two papers published in 2024 examined decades of photometric and spectroscopic data from observers worldwide. Both concluded that the six-year variability could best be explained by the effects of a much smaller, fainter companion star, orbiting unseen within Betelgeuse’s extended atmosphere. Such a companion could cause dust to crowd in certain places along its orbit and clear it out elsewhere, periodically dimming our view of Betelgeuse.

But efforts to find this hypothetical star with Hubble and Chandra turned up nothing — until now.

Discovering Betelgeuse’s old friend

With Gemini North and ‘Alopeke, Howell’s team has detected what earlier studies could only infer. Speckle imagers like ‘Alopeke — Hawaiian for “fox” — use a rapid-fire series of short exposures to overcome atmospheric turbulence and assemble a single high-resolution image that would otherwise be impossible from Earth. With the right conditions and the 8.1-meter mirror of Gemini North, the team was able to directly capture Betelgeuse’s faint stellar neighbor for the first time.

The newly imaged star sits just 52 milliarcseconds (or 0.000014°) from Betelgeuse on the sky. In physical space, it orbits four astronomical units from Betelgeuse, which in our solar system would put it between the outer edge of the main asteroid belt and Jupiter. (One astronomical unit, or AU, is the average Earth-Sun distance.) That puts the star well inside the swollen supergiant’s outer atmosphere.

The companion is estimated to have about 1.5 times the mass of the Sun and shines six magnitudes fainter than Betelgeuse (which is magnitude 0.5) in visible light. Based on its color and brightness, it appears to be an A- or B-type pre-main sequence star — a hot, blue-white object that hasn’t yet begun hydrogen fusion in its core.

“This detection was at the very extremes of what can be accomplished with Gemini in terms of high-angular resolution imaging, and it worked,” Howell said. “This now opens the door for other observational pursuits of a similar nature.”

Implications for red supergiants

The discovery also offers a possible new lens for interpreting variability in red supergiants. Stars like Betelgeuse often show puzzling long-term brightness changes, and Howell’s team notes that the presence of a close-in companion could help explain those cycles — at least in some cases.

The cause of these changes has implications for the size of the star, and thus on its evolutionary phase and how soon it might go supernova. For example, if Betelgeuse’s six-year variability were not due to a companion but rather an intrinsic property, it would be evolved enough to potentially explode within a few dozen to a few hundred years.

But if a companion is causing the long-term variability, Betelgeuse is in a much earlier phase of its life and won’t yet explode for hundreds of thousands of years.

While some red supergiants have been suspected of hosting binary partners before, this marks the first time one has been directly imaged orbiting so close to the star, well within its extended atmosphere.

A doomed dance

As for Betelgeuse and its companion, the two likely formed together. But their end will not be as harmonious. According to the team’s analysis, strong tidal forces will eventually pull the smaller star into the supergiant’s outer layers, dooming it to be consumed within the next 10,000 years. That would likely destabilize Betelgeuse further and perhaps accelerate its eventual supernova.

Astronomers will have their next prime opportunity to study the companion in November 2027, when it reaches greatest elongation — its farthest and most detectable separation from Betelgeuse. Howell and colleagues encourage the community to observe the system around that date to better constrain the companion’s orbit and properties.

The giant’s bracelet

Although not officially named, the research team has suggested a poetic moniker for Betelgeuse’s newfound partner. Since the name Betelgeuse likely derives from the Arabic for “Hand of the Giant,” with Elgeuse being a historic feminine Arabic name used for Orion, they propose the companion be named سوارها , Arabic for “Her Bracelet.”

“The results presented here are not definitive, as the detection is at the limit of the instrument capabilities,” the team writes. “However, the results do present the most direct and substantive evidence for the existence of a stellar companion to Betelgeuse, as well as the properties of that companion.”