Variable stars are a type of stars that regularly vary their brightness, they pulsate. But there is a type of variable star that astronomers have not been able to discern from any regular pattern, until now.

- When we have observed these stars before, we only heard tones without order. It was like listening to a cat go over the keys of a piano, says Tim Bedding, professor of astrophysics at the University of Sydney and lead author of a study published in Nature of the Week.

The clinker became a tune

But now the space-based planetary telescope Tess has observed tens of thousands of stars and 60 of them turned out to be variable stars that have a very low frequency, pulsating at a frequency of about half an hour.

The sound of piano has now become a tune.

 In the clip above you can hear the sound that Tim Bedding refers to. It is the pulsating stars that have been transformed into sound - to give us a feeling for it. The sound is also accelerated.

"These are slow and much more complicated stars than our own," says Oleg Kochukhov, professor of astrophysics at Uppsala University.

The sun is also pulsing

But our own sun also pulses, with a frequency of five minutes. The sun's brightness goes up and down while the radius increases and decreases at the same rate.

- The light from a star tells only what is on the surface, but this vibration is linked to what happens inside the stars, he says.

But why is it important to find out what's going on inside the stars?

- We want to know how the stars work to predict what will happen, and to know what has happened to them. For example, our own sun was 40 percent weaker when life first developed on earth. This is important knowledge for astrobiologists looking for life on other planets, says Oleg Kochukhov.