Galaxy group

Four of the seven members of galaxy group HCG 16[1]

A galaxy group[2] or group of galaxies[3] (GrG[4]) is an aggregation of galaxies comprising about 50 or fewer gravitationally bound members, each at least as luminous as the Milky Way (about 1010 times the luminosity of the Sun); collections of galaxies larger than groups that are first-order clustering are called galaxy clusters.[5] The groups and clusters of galaxies can themselves be clustered, into superclusters of galaxies.

The Milky Way galaxy is part of a group of galaxies called the Local Group.[6]

  1. ^ "Hubble views a bizarre cosmic quartet". Retrieved 19 June 2015.
  2. ^ Bärbel Koribalski (2004). "The NGC 6221/15 Galaxy Group".
  3. ^ Hartmut Frommert & Christine Kronberg. "Groups and Clusters of Galaxies with Messier objects". SEDS.
  4. ^ "Object classification in SIMBAD". SIMBAD. November 2013.
  5. ^ Sparke, L. S. & Gallagher, J. S. (2007). Galaxies in the Universe: an Introduction (2nd ed.). Cambridge University Press. p. 278. ISBN 9780521671866.
  6. ^ Mike Irwin. "The Local Group". Retrieved 2009-11-07.