What is the diameter of this mass concentration of galaxies that contains the Local Sheet?
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Local Sheet The Local Sheet in astronomy is a nearby region of the observable universe where the Milky Way, the members of the Local Group and other galaxies share a similar peculiar velocity. This region lies within a radius of about 7 Mpc , 1.5 Mly thick, and galaxies beyond that distance show markedly different velocities. The Local Group has only a relatively small peculiar velocity of with respect to the Local Sheet. Typical velocity dispersion of galaxies within the Local Sheet is only in the radial direction. All nearby bright galaxies belong to the Local Sheet. The Local Sheet is part of the Local Volume and is in the Virgo Supercluster (Local Supercluster).
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Virgo Supercluster The Virgo Supercluster (Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies that contains the Virgo Cluster in addition to the Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs (110 million light-years). It is one of about 10 million superclusters in the observable universe.
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Virial mass In the context of dark matter halos of galaxies or galaxy clusters, virial mass is the mass within the virial radius formula_1, a radius within which a spherical "top hat" density perturbation destined to become a galaxy is collapsing. This radius is defined as where formula_2 where formula_3 is the halo's average density within that radius, formula_4 is a constant, and formula_5 is the critical density of the universe. (Sometimes in the definition, formula_5 is replaced with the mean density of matter, formula_7, where, at the present day, formula_8 according to data fitted to the Lambda-CDM model.) formula_4 depends on the cosmological model. In an Einstein-de Sitter model it equals formula_10 The virial mass is the mass within this radius and hence is a reasonable measure of the total mass inside a dark matter halo, because beyond that radius the halo blends into the background matter in the universe. This definition is not universal, however, as the exact value of formula_4 depends on the cosmology – in practice, to improve communication, it is sometimes simply assumed that formula_12 and this is signaled by denoting the virial mass as formula_13 and the virial radius as formula_14
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Rosette Nebula The Rosette Nebula (also known as Caldwell 49) is a large spherical H II region (circular in appearance) located near one end of a giant molecular cloud in the Monoceros region of the Milky Way Galaxy. The open cluster NGC 2244 (Caldwell 50) is closely associated with the nebulosity, the stars of the cluster having been formed from the nebula's matter.
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NGC 1579 Coordinates: 04+30/60+09.5/3600&de=35.27194444444444&zoom=ln100000/ln10+1 round 0&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_all 04 30 09.5, +35° 16′ 19″
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Cetus Dwarf Cetus Dwarf is a dwarf spheroidal galaxy. It lies approximately 2.46 Million light-years from Earth. It is an isolated galaxy of the Local Group, which also contains the Milky Way. All of the most readily observable stars in the galaxy are red giants.
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Leo Supercluster The Leo Supercluster is a supercluster in the Northern Celestial Hemisphere that stretches across the constellations Ursa Major and Leo. It covers an area approximately 130 megaparsecs long by 60 megaparsecs wide. The redshifts of member galaxy clusters range from 0.032 to 0.043. The brightest cluster in the system is Abell 1185.
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NGC 4178 NGC 4178 is the "New General Catalogue" identifier for a barred spiral galaxy in the equatorial constellation of Virgo. It was discovered April 11, 1825 by English astronomer John Herschel. Located some 43.8 million light years away, this galaxy spans 2.3 × 0.4 arc minutes and is seen at a low angle, being inclined by 77° to the line of sight from the Earth. The morphological classification of NGC 4178 is SB(rs)dm, indicating that it has a bar feature at the core, and, per the '(rs)', has traces of a ring-like structure surrounding the bar. The 'dm' suffix indicates the spiral arms are diffuse, broken, and irregular in appearance with no bulge at the nucleus. This galaxy is a member of the Virgo Cluster, which is the richest nearby group of galaxies outside the Local Group and forms the core of the Virgo Supercluster.
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Dwarf galaxy problem The dwarf galaxy problem, also known as the missing satellites problem, arises from numerical cosmological simulations that predict the evolution of the distribution of matter in the universe. Dark matter seems to cluster hierarchically and in ever increasing number counts for smaller-and-smaller-sized halos. However, although there seem to be enough observed normal-sized galaxies to account for this distribution, the number of dwarf galaxies is orders of magnitude lower than expected from simulation. For comparison, there were observed to be around 38 dwarf galaxies in the Local Group, and only around 11 orbiting the Milky Way, (for a detailed and more up to date list see List of Milky Way's satellite galaxies) yet one dark matter simulation predicted around 500 Milky Way dwarf satellites.
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Segue 1 Segue 1 is a dwarf spheroidal galaxy or globular cluster situated in the Leo constellation and discovered in 2006 by Sloan Digital Sky Survey. It is located at a distance of about 23 kpc from the Sun and moves away from the Sun with the velocity of about 206 km/s. Segue 1 has a noticeably elongated (ratio of axes ~ 2:1) shape with the half-light radius of about 30 pc. This elongation may be caused by the tidal forces acting from the Milky Way galaxy if Segue 1 is being tidally disrupted now.
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Globular cluster A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is derived from the Latin "globulus"—a small sphere. A globular cluster is sometimes known more simply as a "globular".
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Musket Ball Cluster Coordinates: 09+16/60+10.9/3600&de=29.81222222222222&zoom=ln5200000000/ln10+1 round 0&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_all 09 16 10.9, +29° 48′ 44″
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WISE J000517.48+373720.5 Coordinates: 00+05/60+17.48/3600&de=37.62236111111111&zoom=ln23.2/ln10+1 round 0&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_all 00 05 17.48, +37° 37′ 20.5″
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NGC 4725 NGC 4725 is an intermediate barred spiral galaxy with a prominent ring structure about 40 million light-years away in the constellation Coma Berenices. NGC 4725 is a Seyfert Galaxy, suggesting an active galactic nucleus containing a supermassive black hole.
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GD 165 Coordinates: +09++17/60++13.98/3600&zoom=ln102.9/ln10+1 round 0&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_all 14 24 39.144, +09° 17′ 13.98″
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NGC 5927 NGC 5927 is a globular cluster in the constellation Lupus. NGC 5927 has a diameter of about 12 arcminutes and an apparent magnitude of +8.86. Its Shapley–Sawyer Concentration Class is VIII, and it contains stars of magnitude 15 and dimmer.
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IC 2220 Coordinates: 07+56/60+51.3/3600&de=-59+-07/60+-31/3600&zoom=ln100000/ln10+1 round 0&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_all 07 56 51.3, −59° 07′ 31″
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NGC 6822 NGC 6822 (also known as Barnard's Galaxy, IC 4895, or Caldwell 57) is a barred irregular galaxy approximately 1.6 million light-years away in the constellation Sagittarius. Part of the Local Group of galaxies, it was discovered by E. E. Barnard in 1884 (hence its name), with a six-inch refractor telescope. It is one of the closer galaxies to the Milky Way. It is similar in structure and composition to the Small Magellanic Cloud. It is about 7,000 light-years in diameter.
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NGC 128 NGC 128 is a lenticular galaxy in the constellation Pisces. It is approximately 190 million light-years from earth and has a diameter of about 165,000 light years.
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N44 (emission nebula) N44 is an emission nebula with superbubble structure located in the Large Magellanic Cloud, a satellite galaxy of the Milky Way in the constellation Dorado. Originally catalogued in Karl Henize's "Catalogue of H-alpha emission stars and nebulae in the Magellanic Clouds" of 1956, it is approximately 1,000 light-years wide and 160,000-170,000 light-years distant. N44 has a smaller bubble structure inside known as N44F. The superbubble structure of N44 itself is shaped by the radiation pressure of a 40-star group located near its center; the stars are blue-white, very luminous, and incredibly powerful. N44F has been shaped in a similar manner; it has a hot, massive central star with an unusually powerful stellar wind that moves at 7 million kilometers per hour. This is because it loses material at 100 million times the rate of the Sun, or approximately 1,000,000,000,000,000 tons per year. However, varying density in the N44 nebula has caused the formation of several dust pillars that may conceal star formation. This variable density is likely caused by previous supernovae in the vicinity of N44; many of the stars that have shaped it will eventually also end as supernovae. The past effects of supernovae are also confirmed by the fact that N44 emits x-rays.
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NGC 185 NGC 185 (also known as Caldwell 18) is a dwarf spheroidal galaxy located 2.08 million light-years from Earth, appearing in the constellation Cassiopeia. It is a member of the Local Group, and is a satellite of the Andromeda Galaxy (M31). NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707". John Herschel observed the object again in 1833 when he cataloged it as "h 35", and then in 1864 when he cataloged it as "GC 90" within his "General Catalogue of Nebulae and Clusters". NGC 185 was first photographed between 1898 and 1900 by James Edward Keeler with the Crossley Reflector of Lick Observatory. Unlike most dwarf elliptical galaxies, NGC 185 contains young stellar clusters, and star formation proceeded at a low rate until the recent past. NGC 185 has an active galactic nucleus (AGN) and is usually classified as a type 2 Seyfert galaxy, though its status as a Seyfert is questioned. It is possibly the closest Seyfert galaxy to Earth, and is the only known Seyfert in the Local Group.
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Elias 2-27 Coordinates: ln100000/ln10+1 round 0&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_all 16 26 45.025, -2423° 07.75′ 430″