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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).
For instance, Markarian galaxies, named after Benjamin Markarian, are galaxies with excess blue and ultraviolet emission; [5] galaxies in the Atlas of Peculiar Galaxies are assigned an Arp number after Halton Arp who produced the catalog; etc. Objects in these catalogs are excluded below, except in cases where they carry the name of an ...
Galaxies by type. List of spiral galaxies; List of ring galaxies; List of polar-ring galaxies; List of quasars; Galaxies by association. List of largest galaxies; List of nearest galaxies; Satellite galaxies of the Milky Way; Other characteristics. List of galaxies named after people; List of galaxies with richest globular cluster systems
A comet is named after its first independent discoverers, up to a maximum of three names, separated by hyphens. [ 30 ] [ 31 ] The IAU prefers to credit at most two discoverers, and it credits more than three discoverers only when "in rare cases where named lost comets are identified with a rediscovery that has already received a new name."
2013 – The galaxy Z8 GND 5296 is confirmed by spectroscopy to be one of the most distant galaxies found up to this time. Formed just 700 million years after the Big Bang, expansion of the universe has carried it to its current location, about 13 billion light years away from Earth (30 billion light years comoving distance). [18]
The observable universe contains as many as an estimated 2 trillion galaxies [36] [37] [38] and, overall, as many as an estimated 10 24 stars [39] [40] – more stars (and, potentially, Earth-like planets) than all the grains of beach sand on planet Earth. [41] [42] [43] Other estimates are in the hundreds of billions rather than trillions.
Many dwarf galaxies may orbit a single larger galaxy; the Milky Way has at least a dozen such satellites, with an estimated 300–500 yet to be discovered. [107] Most of the information we have about dwarf galaxies come from observations of the local group, containing two spiral galaxies, the Milky Way and Andromeda, and many dwarf galaxies.
The IAU's names for exoplanets – and on most occasions their host stars – are chosen by the Executive Committee Working Group (ECWG) on Public Naming of Planets and Planetary Satellites, a group working parallel with the Working Group on Star Names (WGSN). [1] Proper names of stars chosen by the ECWG are explicitly recognised by the WGSN. [1]