K. R. Sreenivas

The night sky looks still, but many stars tremble like a drum after a strike. For seven straight years, the TESS satellite stared at the same patches of sky and caught this trembling in 19,151 red giants — old, bloated stars. Previously, far fewer of these 'singing' giants were known, and now the list has grown by 80%.

A red giant is a star that has swelled up, cooled on the outside, and become hundreds of times larger than the Sun. Inside, it's far from calm: layers of gas oscillate like a giant bell, causing its brightness to flicker slightly. Astronomers pick up these oscillations to probe what's happening deep within.