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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 are categorised according to their visual morphology as elliptical, [5] spiral, or irregular. [6] The Milky Way is an example of a spiral galaxy. It is estimated that there are between 200 billion [7] (2 × 10 11) to 2 trillion [8] galaxies in the observable universe.
The observable universe contains as many as an estimated 2 trillion galaxies [95] [96] [97] and, overall, as many as an estimated 10 24 stars [98] [99] – more stars (and earth-like planets) than all the grains of beach sand on planet Earth; [100] [101] [102] but less than the total number of atoms estimated in the universe as 10 82; [103] and ...
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]
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).
The first one to be named was "Halley's Comet" (now officially known as Comet Halley), named after Edmond Halley, who had calculated its orbit. Similarly, the second known periodic comet, Comet Encke (formally designated 2P/Encke), was named after the astronomer, Johann Franz Encke, who had calculated its orbit rather than the original ...
Hubble proved that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually galaxies beyond the Milky Way. [4] He used the strong direct relationship between a classical Cepheid variable 's luminosity and pulsation period [ 5 ] [ 6 ] (discovered in 1908 by Henrietta Swan Leavitt [ 7 ] ) for scaling ...