FG Sagittae

FG Sagittae

A rapidly evolving variable star in the constellation Sagitta that has recently cooled and expanded. It is now a pulsating yellow supergiant but in 1955 was a more compact hot blue supergiant. It is surrounded by a glowing expanding planetary nebula, and it is thought that as the nebula gradually disperses the central star will again heat up and contract before eventually becoming a white dwarf.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006