F. Pepe

A quiet flute melody gets lost in the roar of drums. That's what astronomers face when trying to catch the faint light that has passed through a distant planet's atmosphere while its star blazes nearby. A team of scientists observed WASP-31 b — a hot Jupiter, a gas giant orbiting very close to its star.

Light from a distant star seeps through a planet's gaseous envelope, and astronomers try to guess what that envelope is made of. That's how we study the atmospheres of worlds we can never touch. When a planet passes in front of its sun's disk, its gaseous veil briefly intercepts some of the rays.

A streetlamp flickers as someone walks past. That's roughly how our nearest star, Proxima Centauri, behaves: it flares in response to the motion of its planets. Astronomers observed the star with a highly sensitive instrument, the ESPRESSO spectrograph. It captures light and splits it into colors, much like a prism.