It’s official. The red giant star Betelgeuse in Orion has a companion star, solving a longstanding mystery surrounding its variable brightness.

What’s more, Betelgeuse’s companion star is much smaller and weaker, and will eventually be consumed by its larger sibling.

The companion star was found in a tight orbit around Betelgeuse using the ‘Alopeke instrument on Gemini North, one half of the International Gemini Observatory.

The Betelgeuse mystery

There is a longstanding mystery regarding Betelgeuse’s varying brightness, and this discovery could solve the mystery, but also give astronomers insight into the mechanisms behind other variable red supergiants.

Betelgeuse is one of the brightest stars in the night sky and the closest red supergiant to Earth.

It can be seen as the ‘shoulder’ of the constellation Orion, the Hunter, and even with the naked eye it appears as a large, red point of light in the sky.

Betelgeuse is about 700 times as large as the Sun, but is only about 10 million years old, which is very young by astronomy standards.

For comparison, our own Sun is 4.6 billion years old.

Betelgeuse and its companion star, the companion discovered using ‘Alopeke instrument on the Gemini North telescope, one half of the International Gemini Observatory. Credit: International Gemini Observatory/NOIRLab/NSF/AURA. Image Processing: M. Zamani (NSF NOIRLab). Orion image: NOIRLab in collaboration with Eckhard Slawik

Despite its apparent youth, however, Betelgeuse is currently in the latter stages of its life.

Stargazers have observed Betelgeuse for millennia, and astronomers are well aware of its propensity for changing in brightness over time.

There’s a pattern to its brightness changes, too. It has main period of variability of around 400 days and a more extended, secondary period of around 6 years.

But what’s causing this variability?

Images, taken with the SPHERE instrument on ESO’s Very Large Telescope, show the surface of the red supergiant star Betelgeuse during its unprecedented dimming, which happened in late 2019 and early 2020.

The Great Dimming mystery

Anyone who follows the scientific discoveries surrounding Betelgeuse will remember the sharp decrease in Betelgeuse’s brightness that occurred in 2019 and 2020.

This led some to conclude that Betelgeuse was approaching the stage when it would explode in a supernova.

It’s known that Betelgeuse will some day go supernova, and there have been multiple thought experiments exploring whether Betelgeuse’s supernova will be dangerous to Earth, for example.

Many observers thought this was the moment that the star might finally explode.

However, scientists then determined the dimming was caused by a large cloud of dust ejected by the star.

The Great Dimming mystery was solved.

Betelgeuse and its companion star, the companion discovered using ‘Alopeke instrument on the Gemini North telescope, one half of the International Gemini Observatory. Credit: International Gemini Observatory/NOIRLab/NSF/AURA. Image Processing: M. Zamani (NSF NOIRLab)

Beginning of a Betelgeuse journey

The Great Dimming led some astronomers to take up the job of studying Betelgeuse more regularly, leading to a fresh look at archive data on the star.

In 2024, two papers were released that used archive observations of Betelgeuse and predicted the orbit and location of a companion star, even though it hadn’t been directly observed.

Those papers were entitled Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse and A Buddy for Betelgeuse, respectively.

But then in July 2025, astronomers announced that they had indeed, for the first time, detected that companion star around Betelgeuse.

The Gemini North telescope. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/T. Slovinský

Finding the Betelgeuse companion

A team of astrophysicists led by Steve Howell, a senior research scientist at NASA Ames Research Center, observed Betelgeuse using a speckle imager called ‘Alopeke.

‘Alopeke, which means ‘fox’ in Hawaiian, is mounted on the Gemini North telescope, one half of the International Gemini Observatory.

Speckle imaging is technique that uses short exposure times to counteract the distorting effects of Earth’s wobbly atmosphere on images of the night sky.

It enables higher resolution images, meaning the team were able to directly detect Betelgeuse’s faint companion star.

So what is Betelgeuse’s companion like?

Credit: International Gemini Observatory/NOIRLab/NSF/AURA. Image Processing: M. Zamani (NSF NOIRLab)

The team say it’s 6 magnitudes fainter than Betelgeuse and is about 1.5 times the mass of our Sun

They say it’s probably an A- or B-type pre-main-sequence star: it’s a young, scorching hot, blue-white star that’s not yet begun hydrogen burning in its core.

And it’s pretty close to Betelgeuse, just four times the distance between the Earth and the Sun.

This is the first time a close stellar companion has been detected orbiting a supergiant star.

And the companion orbits within Betelgeuse’s outer extended atmosphere, meaning its detection is quite a technical feat.

“Gemini North’s ability to obtain high angular resolutions and sharp contrasts allowed the companion of Betelgeuse to be directly detected,” says Howell.

“Papers that predicted Betelgeuse’s companion believed that no one would likely ever be able to image it.”

Betelgeuse, as seen by the Atacama Large Millimeter/submillimeter Array (ALMA). Credit: ESO

What this means

The discovery suggests Betelgeuse and its companion star were likely born at the same time.

But Betelgeuse’s companion will have a short life, because strong ‘tidal forces’ caused by Betelgeuse’s stronger gravitational pull will cause the companion to spiral into Betelgeuse.

It will meet its demise within the next 10,000 years.

“This detection was at the very extremes of what can be accomplished with Gemini in terms of high-angular resolution imaging, and it worked,” says Howell.

“This now opens the door for other observational pursuits of a similar nature.”

“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,” says Martin Still, NSF program director for the International Gemini Observatory.

“Delivering the solution to the Betelgeuse problem that has stood for hundreds of years will stand as an evocative highlight achievement.”

Astronomers say there’ll be another chance to study Betelgeuse’s companion in November 2027 when it will be further separated from Betelgeuse, and therefore easier to see.

When this happens, the team should be able to get a better look at the companion and discover even more about it.

The research is presented in a paper called Probable Direct Imaging Discovery of the Stellar Companion to Betelgeuse, appearing in The Astrophysical Journal Letters on 24 July 2025.