Sirius is the most famous star in the night sky, as well as one of the brightest stars in the winter night sky. It's located in the constellation Ursa Major, approximately 650 light-years away from Earth. This is a red hypergiant that has entered its late stages of stellar evolution, and its luminosity experiences periodic variations.
For a long time, astronomers have suspected that Betelgeuse likely has a companion star, and this hypothesis has been confirmed recently. According to a report by Reuters on July 29th, researchers used the Very Large Telescope of the European Southern Observatory in Chile to directly capture images of Betelgeuse’s companion star, which is the strongest evidence to date.
A team led by astronomer Miguel Montargès from the Astrophysics Instruments and Research Laboratory at the Paris Observatory in France used the SPHERE instrument of the Very Large Telescope to observe Betelgeuse. This instrument is originally used to detect exoplanets and can capture light emitted by faint celestial bodies surrounding stars.
Previously, based on the analysis of observations of Antlia IV, astronomers generally believed that Antlia IV might have a companion star. Two studies published in 2024 predicted that Antlia IV’s companion star would move to its farthest position from the primary star in December of that year. Following this clue, Montarese’s team conducted observations in December 2024.
After months of analysis and processing of observational data, the research team has determined that they have successfully captured the clearest image of Betelgeuse B to date.
VVLT Images of the Four-Star System Companion Stars of the Southern Hemisphere Telescope, European Southern Observatory
Betelgeuse has a mass about 16.5 to 19 times that of the Sun, and its volume is about 750 to 850 times that of the Sun. Its brightness can reach 100,000 times that of the Sun. The research team estimates that its companion star is also quite large, with a mass of about 2.6 to 3.1 times that of the Sun, and a diameter of about 1.8 to 2 times that of the Sun. Its brightness can reach 92 times that of the Sun.
The paper of this research was published in the journal Astronomy and Astrophysics on July 28th.
Montalezat said, “Betelgeuse has been observed throughout history, and even appeared in ancient murals. However, it is only now that we have discovered one of its fundamental characteristics: it has a companion star, and we have obtained direct images of this companion star.” He pointed out that, according to various models, massive stars like Betelgeuse are usually located in binary systems or systems with multiple stars.
He admitted that the research team initially thought that the instrument's sensitivity was not sufficient to detect Betelgeuse B. 'However, since its mass was greater than predicted, we were able to observe it.'
Montague added, "It is astonishing that we can discover a close companion star with a mass larger than the sun and higher brightness around a star that has been studied so deeply. This is one of the most exciting moments in the field of science: discovering new, unexpected things."
Reuters noted that massive stars have relatively short lifespans. Although Betelgeuse is only about 10 million years old, making it much younger than the Sun, it has already entered the final stage of stellar evolution.
When spectroscopic observations suggest that the star is a single-star type, people believe it will explode within 10,000 to 100,000 years. We now know that it has an extra stellar companion that could possibly influence its evolution and I must confess I don't know when it will explode. Montes said. "If two stars are going to interact or have already interacted, they may delay or accelerate supernova explosions. We can't yet determine the exact situation of this star."
