Galaxy Groups and Clusters

Galaxy groups and clusters are the largest known gravitationally bound objects to have arisen thus far in the process of cosmic structure formation. They form the densest part of the large scale structure of the Universe. In models for the gravitational formation of structure with cold dark matter, the smallest structures collapse first and eventually build the largest structures, clusters of galaxies. Clusters are then formed relatively recently between 10 billion years ago and now. Groups and clusters may contain ten to thousands of individual galaxies. The clusters themselves are often associated with larger, non-gravitationally bound, groups called superclusters.

Read more about Galaxy Groups And Clusters:  Groups of Galaxies, Clusters of Galaxies, Observational Methods, Temperature and Density, List of Groups and Clusters

Famous quotes containing the words galaxy, groups and/or clusters:

    for it is not so much to know the self
    as to know it as it is known
    by galaxy and cedar cone,
    as if birth had never found it

    and death could never end it:
    Archie Randolph Ammons (b. 1926)

    Women over fifty already form one of the largest groups in the population structure of the western world. As long as they like themselves, they will not be an oppressed minority. In order to like themselves they must reject trivialization by others of who and what they are. A grown woman should not have to masquerade as a girl in order to remain in the land of the living.
    Germaine Greer (b. 1939)

    Where we such clusters had,
    As made us nobly wild, not mad;
    And yet each verse of thine
    Outdid the meat, outdid the frolic wine.
    Robert Herrick (1591–1674)