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Size (left) and distance (right) of a few well-known galaxies put to scale. There are an estimated 100 billion galaxies in all of the observable universe. [1] On the order of 100,000 galaxies make up the Local Supercluster, and about 51 galaxies are in the Local Group (see list of nearest galaxies for a complete list).
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek galaxias, literally 'milky', a reference to the Milky Way galaxy that contains the Solar System.
This is a list of largest galaxies known, sorted by order of increasing major axis diameters. The unit of measurement used is the light-year (approximately 9.46 × 10 12 kilometers). Overview
Many galaxies are thought to have black holes at their active centers. The Milky Way's central black hole, known as Sagittarius A* , has a mass four million times greater than the Sun. As of March 2016, GN-z11 is the oldest and most distant observed galaxy with a comoving distance of 32 billion light-years from Earth, and observed as it existed ...
The spread of velocities for the individual galaxies is about 150 km/s. However, this definition should be used as a guide only, as larger and more massive galaxy systems are sometimes classified as galaxy groups. [4] Groups are the most common structures of galaxies in the universe, comprising at least 50% of the galaxies in the local universe.
This was the first noted cluster of "nebulae" that would become galaxies. The first redshifts to galaxies in the cluster were measured in the 1910s. Galaxies were not identified as such until the 1920s. The distance to the Virgo Cluster would have to wait until the 1930s. [21] Mly represents millions of light-years, a measure of distance.
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The astronomical catalogue is composed mainly of star clusters, nebulae, and galaxies. Other objects in the catalogue can be found in the other subpages of the list of NGC objects . The constellation information in these tables is from The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer , [ 1 ...