Stephan’s Quintet in the constellation Pegasus is an optical group of five galaxies, four of which are the first compact galaxy group ever discovered.

Shock waves created by a collision between Stefan’s quintet galaxies and an invading galaxy drive various processes in the intergalactic medium, a thin cloud of hot hydrogen plasma that exists in the intergalactic space.

This violent intrusion of Stephan’s Quintet sets off a “recycling plant” for hot and cold molecular hydrogen gas between the five galaxies, triggering a shock wave several times the size of the Milky Way that flows through the interstellar plasma. In addition, astronomers discovered that a giant cloud of gas breaks up to form a less dense “fog” of hot gas. JWST/ALMA observations show the formation of a tail of hot gas that could be a collision between two clouds, and even the formation of a new galaxy.

Discovering these phenomena will help scientists better understand how turbulence affects the intergalactic medium and affects star formation and galaxy evolution in general.