Ringing Beat

Heartbeats and ringing bells don’t seem to go together. But they’re a perfect match in a set of stars discovered by the Kepler space telescope.

The spacecraft hunts for planets orbiting other stars by staring at the same patch of sky non-stop. That steady vision also allows it to see changes in stars.

For example, it’s discovered binary systems where the distance between the two stars varies dramatically. When the stars are far apart, they’re round, like normal stars. But when they come close together, their gravitational pull distorts one or both stars, making them much bigger around the middle. That increases the surface area of the stars, so they look brighter. And that’s where the heartbeat comes in. When you plot the brightness of one of those stars, it looks a lot like an EKG, with a long, steady line followed by a large, brief spike.

The bell part of the story describes what happens to the stars’ interiors. Researchers say the effect of a close approach is like a mallet strik