What is "photoevaporation"

n. (context astronomy English) The removal of the atmosphere of a planet (or the disk of a protoplanet) by high-energy photons from its sun or a nearby hot star

Photoevaporation denotes the process where energetic radiation ionises gas and causes it to disperse away from the ionising source. This typically refers to an astrophysical context where ultraviolet radiation from hot stars acts on clouds of material such as molecular clouds, protoplanetary disks, or planetary atmospheres.