Heartbeat Stars

Stars are big and heavy, but they’re not solid. Because they’re made of gas, they’re just about as easy to stretch and squish as a blob of Silly Putty. Stars that spin very fast, for example, bulge out at the equator, so they look like flattened beachballs. And stars in certain stages of life puff in and out like a set of breathing lungs.

And astronomers using a space telescope have recently discovered binary stars that get stretched out, then wiggle like a bowl of Jell-O when they spring back to a rounder shape.

The Kepler satellite was built to look for planets in other star systems. But its observations also reveal details about the stars.

An example is “heartbeat” stars. They got the name because, when you plot how bright they are, the line looks like a chart of a beating heart, with regular peaks and valleys.

A recent study found that these systems consist of two stars in an elongated orbit around each other. At their closest, the stars may be separated by only a few times the size of the stars themselves. The gravity of each star tugs on the other, stretching the star out. The increased surface area of the two stars makes the system brighter. When the stars move away from each other, they snap back to a rounder shape, so they get fainter.

As they change to a more spherical shape, though, their surfaces jiggle. Astronomers may someday use the jiggles to probe conditions inside the stars — stars that are constantly changing shape.

Script by Damond Benningfield