Portal:Astronomy/Picture/8 May 2005

Hoag's Object is a ring galaxy, consisting of a symmetrical ring of young, hot blue stars surrounding a central nucleus of older yellow stars. The cause of its structure is not known: some galaxies of this time are formed by galactic collisions, but there seem to be no nearby candidates for the galaxy which collided with Hoag's Object. Credit: NASA and the Hubble Heritage Team