Astronomers see the expected companion star of Betelgeuse for the first time

Betelgeuse remains one of the brightest stars in the sky and the closest red giant to Earth.

For thousands of years, astronomers have observed Betelgeuse, which appeared to be alone in the night sky. However, thanks to a powerful speckle interferometer camera mounted on the Gemini North telescope, astronomers have finally managed to detect Betelgeuse’s companion star.

It is noted, that the companion star is very close to Betelgeuse. The speckle imaging technology freezes atmospheric distortions due to fast exposure, which allows astronomers to obtain extremely clear images.

With the help of the 8.1-meter Gemini North mirror, astronomers were able to directly see Betelgeuse’s hidden neighbor star. In 2019-2020, astronomers observed a sudden decrease in Betelgeuse’s brightness, called the «Great Eclipse». Initially, scientists assumed that a supernova outburst might soon occur, but later it became known that the eclipse was caused by a dust cloud released by the star.

This prompted astronomers to review the archival data and subsequently led to the discovery of the companion star Betelgeuse. This star is about 6 times dimmer than Betelgeuse in the visible light spectrum. It orbits inside the star’s extended atmosphere, causing it to be almost impossible to detect until now.

Astronomers led by Steve Howell NASA’s Ames Center used a speckle camera «Alopeke» to obtain high-contrast images with a short exposure time, in which the dim star stood out against the bright glow of Betelgeuse. 

As emphasized by Steve Howell, the Gemini North’s ability to capture images with high angular resolution and sharp contrasts has enabled detect a star in a pair with Betelgeuse. The analysis of the star’s light showed that it has not yet entered the main sequence and represents a class A or B luminary. It is a hot, white-blue star that is still in its infancy and has not yet begun hydrogen fusion. 

The mass of this star is about 1.5 times that of the Sun. Its orbit is located at a distance equal to only four distances from the Earth to the Sun, around Betelgeuse. This is the first time that a supergiant star has ever been found to have a pair. 

This may explain the mysterious six-year cycle of brightness changes Betelgeuse. Astronomers have long guessed that the star must have a companion, but they have not been able to detect it. Betelgeuse, 10 million years old, is at the end of its life cycle and, according to astronomers, is expected to explode in a supernova in the next 100,000 years. 

However, the neighboring star has much less time. It is expected that in the next 10 thousand years tidal forces will attract the young star to Betelgeuse and the merger will take place. Another opportunity to study Betelgeuse’s stellar companion will come in November 2027, when it will be at the maximum distance from Betelgeuse, where it is easiest to detect.

The results of the study are published in The Astrophysical Journal Letters

Source: Phys.org; Interesting Engineering