Astronomers have captured images of what is thought to be Betelgeuse’s stellar companion – not only detecting a star orbiting a supergiant in a world-first, but solving a mystery that has puzzled astrophysicists for centuries. The research was published in The Astrophysical Journal Letters.
Betelgeuse: A Stellar Mystery
Betelgeuse is our closest red supergiant – an orange-red star that expands in size as it approaches the end of its life. It lies approximately 700 lightyears from planet Earth in the constellation Orion and boasts a radius around 700 times larger than that of the Sun.
It also has the distinction of being one of the brightest stars in the night sky. Though this brightness is known to fluctuate – a fact that has been documented by scientists for 200 years or so, and has been reported by Aboriginal societies for much longer. The supergiant experiences a main period of variability that lasts for roughly 400 days and a more extended secondary period of variability lasting approximately six years.
One explanation put forward for this variation is the existence of a companion star. Only, until now, there were no observations to confirm this hypothesis.
Read More: Is Betelgeuse About to Become a Supernova?
A Speckle in Space
Steve Howell, a senior research scientist at NASA Ames Research Centre, and his team deployed a speckle imager called “Alopeke,” Hawaiian for “fox,” which was attached to the Gemini North telescope. Using speckle imaging enabled the astronomers to avoid atmospheric distortions because its short exposure time allows thousands of images to be taken in quick succession. Information is extracted from these short exposures to produce a high-resolution image.
The team specifically looked at two sets of observations – one from 2020 and a second from 2024. The first were taken during the “Great Dimming” event, in which there was a dramatic drop in Betelgeuse’s brightness that led some to speculate an impending supernova death. It was later confirmed to be the result of a dust cloud. There were no signs of a companion star in these observations, most likely because Betelgeuse eclipsed the star. However, there was evidence for a companion star in the second set of observations from 2024.
“Gemini North’s ability to obtain high angular resolutions and sharp contrasts allowed the companion of Betelgeuse to be directly detected,” Howell said in a press release. “Papers that predicted Betelgeuse’s companion believed that no one would likely ever be able to image it.”
From the images, the researchers calculated the distance between Betelgeuse and the companion star and determined the gap between the two was approximately four times that between the Earth and the Sun.
Data suggests the companion is an A- or B-type pre-main-sequence star. This means it is young, emits a blue-white light and has not started burning hydrogen in its core. It is thought to be one and a half times larger than the Sun and six times fainter than Betelgeuse.
Read More: When Will Betelgeuse Explode?
An Untimely End
Findings from Alopeke not only help explain why Betelgeuse experiences periods of relative dimness, but could offer clues to its past and future. Despite being at very different life stages, both Betelgeuse and its companion are likely to have started life at the same time. It is thought the latter will eventually crash into its larger neighbor as a result of powerful tidal forces, leading to its death – an event Howell and his team predict will happen in the next 10,000 years.
“Delivering the solution to the Betelgeuse problem that has stood for hundreds of years will stand as an evocative highlight achievement,” Martin Still, NSF program director for the International Gemini Observatory, said in a press release. The team hopes the methods used in the study will enable equally exciting discoveries in the future.
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
The Astrophysical Journal Letters. The Probable Direct-imaging Detection of the Stellar Companion to Betelgeuse
Rosie McCall is a freelance writer living in London. She has covered science and health topics for publications, including IFLScience, Newsweek, and Health.
