Be stars have always been a fascinating mystery to astronomers. They are a subset of the bright B-type stars. Unlike normal B stars, Be stars rotate very quickly and create rings of material around their orbits, something that is not seen in other types of stars and has not yet been specifically explained.
By analyzing data from two powerful satellites, Gaia and Hipparcos, researchers from the University of Leeds (UK) showed that Be's strange characteristics are due to interactions with two companions.
The "monster" Be star and the victim star in the distance, stripped of its outer parts. (Graphic: ESO)
Be is thought to be a type of cosmic "vampire". The theory is that this type of monster evolved from a binary star system consisting of two stars orbiting a common center.
Be "hunts" and its smaller companions as victims. Matter from the victims is sucked in by it, creating a ring of matter around itself, while also accumulating more angular momentum to increase its rotation speed.
In the new study, scientists focused on one problem: The range of binary star systems orbiting the same center seems too large for the Be star to hunt down and "suck" its companion.
That's a tough answer to find, since only 28% of Be stars have been identified with a companion. One theory is that the companion star has become too faint to observe after being "sucking blood" for so long.
Looking at data on other stellar types where a star has been stripped of material by a companion, scientists concluded that Be is likely part of a system of more than two stars.
In it, the third star acts as the "vampire's assistant", orbiting in a larger orbit outside the Be star and the "victim" star.
The chaos of the three-star system gave this hidden assistant the opportunity to push the victim star closer to the Be star, while it itself retreated.
The close enough distance has helped Be "eat" more easily, develop better to achieve the "monster" state that astronomers often observe.
(Source: Nguoi Lao Dong)
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