Accretion (astrophysics)

astrophysical process in which matter gravitationally collects into a massive object

Accretion is the process of growth or increase of astronomical bodies due to gravity. Typically it occurs by the gradual accumulation of additional layers of matter. See Formation and evolution of the Solar System for a discussion.

Atacama Large Millimeter Array image of HL Tauri, a protoplanetary disk.