Kiyoaki Doi

The young star PDS 66 is surrounded by a flat disk of gas and dust — the cradle of future planets. In the cold outer regions of such a disk, silicon and sulfur are usually hidden inside dust grains, but astronomers spotted a bright patch of gas at about 60 astronomical units from the star.

When a giant planet grows, it pulls in gas. Some of that gas swirls around it into a small disk — called a circumplanetary disk. It is in such disks that moons are thought to form. For the planet PDS 70 c, located 370 light-years away, such a disk was directly observed using the ALMA antenna array in the millimeter range.