At three locations in the protoplanetary disk around HD 163296, a young star located approximately 400 light-years away in the constellation Sagittarius, gas is flowing like a waterfall into gaps that are most likely caused by planets in formation. An artist’s impression of gas flowing like a waterfall into a protoplanetary disk gap, which is most likely caused by an infant planet. Image credit: NRAO / AUI / NSF / S. Dagnello. Protoplanetary disks...