Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have conducted one of the deepest surveys ever of protoplanetary disks — quasi-steady circumstellar disks of gas and dust, from which planets may eventually form or be in the process of forming. ALMA’s high-resolution images of nearby protoplanetary disks. Image credit: ALMA / ESO / NAOJ / NRAO / S. Andrews et al / AUI / NSF / S. Dagnello. The leading models for planet...