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An astronomer could probably spend an entire career studying a busy star system in the constellation Lyra. It’s a dynamic system in which two stars are changing as we watch.
Beta Lyrae is about a thousand light-years away. The system appears to consist of several stars. But the most interesting are two that are quite close together — they’re only a few million miles apart.
The stars probably were born about 25 million years ago. A study last year said that one of them was born about 10 times the mass of the Sun, with the other only seven times the Sun’s mass.
The heavier star evolved faster, so it reached the end of its life more quickly. It puffed up to become a giant. The gravity of the companion pulled on the closer side of the giant, sculpting it into the shape of a teardrop.
Gas began flowing from the narrow end of the teardrop toward the companion, and is still flowing today. The gas forms a swirling disk around the star. As gas funnels from the disk onto the star, it makes the star spin faster. That flattens the star a bit, so it looks more like a lozenge than a ball.
The donor star has dumped most of its mass onto the companion. So the once-heavier star is now only about a quarter the mass of its companion. And the process continues to play out, as one star gets bigger and the other gets smaller.
Look for Lyra high overhead as night falls, marked by its brightest star, Vega. Beta Lyrae is close by — a fainter star with an interesting story.
Script by Damond Benningfield