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In Hermann–Mauguin notation, space groups are named by a symbol combining the point group identifier with the uppercase letters describing the lattice type. Translations within the lattice in the form of screw axes and glide planes are also noted, giving a complete crystallographic space group. These are the Bravais lattices in three dimensions:
A space group is called symmorphic (or split) if there is a point such that all symmetries are the product of a symmetry fixing this point and a translation. Equivalently, a space group is symmorphic if it is a semidirect product of its point group with its translation subgroup. There are 73 symmorphic space groups, with exactly one in each ...
The group is, therefore, more properly called HCG 79; the name refers to the visual collection and not the group. HCG 79 lies 190 million light-years away in the Serpens Caput constellation. Stephan's Quintet (Stephan's Quartet) Named after its discoverer, Édouard Stephan.
In the 1980s, the Lyons Groups of Galaxies listed 485 galaxy groups with 3,933 member galaxies. Galaxy Zoo is a project aiming at a more comprehensive list: launched in July 2007, it has classified over one million galaxy images from The Sloan Digital Sky Survey, The Hubble Space Telescope and the Cosmic Assembly Near-Infrared Deep ...
Groups are the most common structures of galaxies in the universe, comprising at least 50% of the galaxies in the local universe. Groups have a mass range between those of the very large elliptical galaxies and clusters of galaxies. [5] Our own galaxy, the Milky Way, is contained in the Local Group of more than 54 galaxies. [6]
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 10 10 times the luminosity of the Sun); collections of galaxies larger than groups that are first-order clustering are called galaxy clusters. [5]
The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It has a total diameter of roughly 3 megaparsecs (10 million light-years ; 9 × 10 19 kilometres ), [ 1 ] and a total mass of the order of 2 × 10 12 solar masses (4 × 10 42 kg). [ 2 ]
This is a list of the largest cosmic structures so far discovered. The unit of measurement used is the light-year (distance traveled by light in one Julian year; approximately 9.46 trillion kilometres). This list includes superclusters, galaxy filaments and large quasar groups (LQGs). The structures are listed based on their longest dimension.