Astronomers use many techniques to find planets in other star systems. One of those is looking where there doesn’t appear to be anything — wide gaps in disks of dust around young stars. Most of these stars are only a few million years old — billions of years younger than the Sun. They’re encircled by cold dust — raw materials for making planets.
The disks are easy targets for ALMA — an array of telescopes in Chile that studies a form of radio waves. It sees the disks in good detail. And most of the disks have wide gaps — zones with very little dust. Such regions could have been cleared out by the gravity of orbiting planets. So astronomers are trying to find those planets.
One system where they’ve been successful is A-b Aurigae. It’s more than 500 light-years away, in Auriga, the charioteer. The constellation is high overhead at nightfall, although the star is too faint to see without a telescope.
The star is bigger and heavier than the Sun. But it’s an infant — it’s not yet fully formed. It’s encircled by a giant disk. And observations have revealed a likely planet in a gap in the disk. The planet is bigger and heavier than Jupiter, the giant of our own solar system. It’s so far out that it takes hundreds of years to orbit the star. But that helped make it a little easier to spot. In fact, astronomers found it by taking its picture — a planet discovered lurking in a dark zone around an infant star.