Betelgeuse’s long-lost companion emerges from the shadows

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

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

An iconic star

Betelgeuse is among the most iconic stars within the night time sky, famed not just for its ruddy hue and place at Orion’s shoulder, but in addition for its turbulent and unpredictable nature. Located about 650 light-years away, the star is a real big, spanning practically 700 instances the Sun’s radius. Though solely 10 million years outdated, Betelgeuse is already nearing the top of its life.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 consideration in 2019 and 2020, when Betelgeuse unexpectedly dimmed so drastically that some believed its supernova is perhaps imminent. The occasion, now referred to as the “Great Dimming,” was finally blamed on a veil of mud ejected by the star itself. But it additionally prompted astronomers to take a more in-depth take a look at what is perhaps lurking in Betelgeuse’s glow.

Two papers printed in 2024 examined many years of photometric and spectroscopic information from observers worldwide. Both concluded that the six-year variability might greatest be defined by the consequences of a a lot smaller, fainter companion star, orbiting unseen inside Betelgeuse’s prolonged environment. Such a companion might trigger mud to crowd in sure locations alongside its orbit and clear it out elsewhere, periodically dimming our view of Betelgeuse. 

But efforts to seek out this hypothetical star with Hubble and Chandra turned up nothing — till now.

Discovering Betelgeuse’s outdated pal

With Gemini North and ‘Alopeke, Howell’s workforce has detected what earlier research might solely 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 primary time.

The newly imaged star sits simply 52 milliarcseconds (or 0.000014°) from Betelgeuse on the sky. In bodily area, it orbits 4 astronomical models from Betelgeuse, which in our photo voltaic system would put it between the outer fringe of the principle asteroid belt and Jupiter. (One astronomical unit, or AU, is the typical Earth-Sun distance.) That places the star effectively contained in the swollen supergiant’s outer environment.

The companion is estimated to have about 1.5 instances the mass of the Sun and shines six magnitudes fainter than Betelgeuse (which is magnitude 0.5) in seen mild. Based on its colour and brightness, it seems to be an A- or B-type pre-main sequence star — a scorching, blue-white object that hasn’t but 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 mentioned. “This now opens the door for other observational pursuits of a similar nature.”

Implications for purple supergiants

The discovery additionally provides a attainable new lens for deciphering variability in purple supergiants. Stars like Betelgeuse typically present puzzling long-term brightness adjustments, and Howell’s workforce notes that the presence of a close-in companion might assist clarify these cycles — no less than in some circumstances. 

The trigger of those adjustments has implications for the scale of the star, and thus on its evolutionary section and the way quickly it’d go supernova. For instance, if Betelgeuse’s six-year variability have been not as a consequence of a companion however quite an intrinsic property, it could be developed sufficient to probably explode inside just a few dozen to a couple hundred years. 

But if a companion is inflicting the long-term variability, Betelgeuse is in a a lot earlier section of its life and received’t but explode for a whole bunch of 1000’s of years. 

While some purple supergiants have been suspected of internet hosting binary companions earlier than, this marks the primary time one has been instantly imaged orbiting so near the star, effectively inside its prolonged environment.

A doomed dance

As for Betelgeuse and its companion, the 2 possible shaped collectively. But their finish is not going to be as harmonious. According to the workforce’s evaluation, sturdy tidal forces will finally pull the smaller star into the supergiant’s outer layers, dooming it to be consumed throughout the subsequent 10,000 years. That would possible destabilize Betelgeuse additional and maybe speed up its eventual supernova.

Astronomers could have their subsequent prime alternative to review the companion in November 2027, when it reaches biggest elongation — its farthest and most detectable separation from Betelgeuse. Howell and colleagues encourage the neighborhood to look at the system round that date to higher constrain the companion’s orbit and properties.

The big’s bracelet

Although not formally named, the analysis workforce has steered a poetic moniker for Betelgeuse’s newfound companion. Since the title Betelgeuse possible derives from the Arabic for “Hand of the Giant,” with Elgeuse being a historic female Arabic title used for Orion, they suggest 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 workforce 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.”