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28-555: A 2014 study indicates that the Local Supercluster is only a part of an even greater supercluster, Laniakea , a larger group centered on the Great Attractor , thus subsuming the former Virgo Supercluster under Laniakea. Beginning with the first large sample of nebulae published by William and John Herschel in 1863, it was known that there is a marked excess of nebular fields in the constellation Virgo , near

56-651: A " dumbbell " shape; the Milky Way and its satellites form one lobe, and the Andromeda Galaxy and its satellites constitute the other. The two collections are separated by about 800 kiloparsecs (3 × 10 ^  ly; 2 × 10  km) and are moving toward one another with a velocity of 123 km/s . The group itself is a part of the larger Virgo Supercluster , which may be a part of the Laniakea Supercluster . The exact number of galaxies in

84-711: A figure that is consistent with results obtained for other superclusters. By comparison, the mass-to-light ratio for the Milky Way is 63.8 assuming a solar absolute magnitude of 4.83, a Milky Way absolute magnitude of −20.9, and a Milky Way mass of 1.25 × 10  M ☉ . These ratios are one of the main arguments in favor of the presence of large amounts of dark matter in the universe; if dark matter did not exist, much smaller mass-to-light ratios would be expected. Laniakea Supercluster The Laniakea Supercluster ( / ˌ l ɑː n i . ə ˈ k eɪ . ə / ; Hawaiian for "open skies" or "immense heaven") or

112-551: A mass of approximately 5 × 10   M ☉ (1 × 10  kg), and is the third spiral galaxy. It is unclear whether the Triangulum Galaxy is a companion of the Andromeda Galaxy; the two galaxies are 750,000 light years apart, and experienced a close passage 2–4 billion years ago which triggered star formation across Andromeda's disk. The Pisces Dwarf Galaxy is equidistant from the Andromeda Galaxy and

140-787: A new way of defining superclusters according to the relative velocities of galaxies. The new definition of the local supercluster subsumes the prior defined Virgo and Hydra-Centaurus Supercluster as appendages, the former being the prior defined local supercluster. Follow-up studies suggest that the Laniakea Supercluster is not gravitationally bound. It will disperse rather than continue to maintain itself as an overdensity relative to surrounding areas. The name laniākea ( [ˈlɐnijaːˈkɛjə] ) means 'immense heaven' in Hawaiian , from lani  'heaven' and ākea  'spacious, immeasurable'. The name

168-564: Is almost the same as that of the Horologium Supercluster . It consists of four subparts, which were known previously as separate superclusters: The most massive galaxy clusters of the Laniakea Supercluster are Virgo , Hydra , Centaurus , Abell 3565 , Abell 3574 , Abell 3521 , Fornax , Eridanus , and Norma . The entire supercluster consists of approximately 300 to 500 known galaxy clusters and groups. The real number may be much larger because some of these are traversing

196-704: Is experiencing a bulk flow on the order of 600 km/s in the direction of the Norma Cluster (Abell 3627) . Lynden-Bell et al. (1988) dubbed the cause of this the " Great Attractor ". The Great Attractor is now understood to be the center of mass of an even larger structure of galaxy clusters, dubbed " Laniakea ", which includes the Virgo Supercluster (including the Local Group) as well as the Hydra-Centaurus Supercluster,

224-515: Is isolated in the general field" and delineated, by decreasing luminosity, its members to be M31 , Milky Way , M33 , Large Magellanic Cloud , Small Magellanic Cloud , M32 , NGC 205 , NGC 6822 , NGC 185 , IC 1613 and NGC 147 . He also identified IC 10 as a possible part of the Local Group. mass: 7 × 10 M ☉ The galaxies of the Local Group are likely to merge together under their own mutual gravitational attractions over

252-588: Is roughly 7,000 times that of the Local Group, or 100 billion times that of the Milky Way. The number density of galaxies in the LS falls off with the square of the distance from its center near the Virgo Cluster , suggesting that this cluster is not randomly located. Overall, the vast majority of the luminous galaxies (less than absolute magnitude −13) are concentrated in a small number of clouds (groups of galaxy clusters ). Ninety-eight percent can be found in

280-529: Is uncertain whether these are companion galaxies of the Andromeda Galaxy Local Group 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 kilometres ), and a total mass of the order of 2 × 10 solar masses (4 × 10  kg). It consists of two collections of galaxies in

308-475: The Antlia Dwarf Galaxy as well as Sextans B , Leo P , Antlia B and possibly Leo A , is uncertain due to extreme distances from the center of the Local Group. The Antlia-Sextans Group is unlikely to be gravitationally bound to the Local Group due to probably lying outside the Local Group's Zero-velocity surface —which would make it a true galaxy group of its own rather than a subgroup within

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336-694: The Local Supercluster ( LSC or LS ) is the galaxy supercluster that is home to the Milky Way and approximately 100,000 other nearby galaxies. It was defined in September 2014, when a group of astronomers including R. Brent Tully of the University of Hawaiʻi , Hélène Courtois of the University of Lyon , Yehuda Hoffman of the Hebrew University of Jerusalem , and Daniel Pomarède of CEA Université Paris-Saclay published

364-487: The Zone of Avoidance , an area of the sky that is partially obscured by gas and dust from the Milky Way galaxy, making them essentially undetectable. Superclusters are some of the universe 's largest structures and have boundaries that are difficult to define, especially from the inside. Within a given supercluster, most galaxy motions will be directed inward, toward the center of mass . This gravitational focal point, in

392-563: The 1980s already suggested that several of the superclusters then known might be connected. For example, South African astronomer Tony Fairall stated in 1988 that redshifts suggested that the Virgo and Hydra–Centaurus superclusters may be connected. The neighboring superclusters to the Laniakea Supercluster are the Shapley Supercluster , Hercules Supercluster , Coma Supercluster , and Perseus–Pisces Supercluster . The edges of

420-470: The LS to other superclusters. The LS represents a typical poor (that is, lacking a high density core) supercluster of rather small size. It has one rich galaxy cluster in the center, surrounded by filaments of galaxies and poor groups. The Local Group is located on the outskirts of the LS in a small filament extending from the Fornax Cluster to the Virgo Cluster . The Virgo Supercluster's volume

448-504: The LS. It consists of two components: an appreciably flattened disk containing two thirds of the supercluster's luminous galaxies, and a roughly spherical halo containing the remaining third. The disk itself is a thin (~1 Mpc ) ellipsoid with a long axis / short axis ratio of at least 6 to 1, and possibly as high as 9 to 1. Data released in June 2003 from the 5-year Two-degree-Field Galaxy Redshift Survey (2dF) has allowed astronomers to compare

476-474: The Local Group is unknown as some are occluded by the Milky Way; however, at least 80 members are known, most of which are dwarf galaxies . The two largest members, the Andromeda and the Milky Way galaxies, are both spiral galaxies with masses of about 10 solar masses each. Each has its own system of satellite galaxies : The Triangulum Galaxy (M33) is the third-largest member of the Local Group, with

504-604: The Local Group. This possible independence may, however, disappear as the Milky Way continues coalescing with Andromeda due to the increased mass, and density thereof, plausibly widening the radius of the zero-velocity surface of the Local Group. The term "The Local Group" was introduced by Edwin Hubble in Chapter VI of his 1936 book The Realm of the Nebulae . There, he described it as "a typical small group of nebulae which

532-400: The Local Supercluster (LS) was actually a structure or a chance alignment of galaxies. The issue was resolved with the large redshift surveys of the late 1970s and early 1980s, which convincingly showed the flattened concentration of galaxies along the supergalactic plane. In a comprehensive 1982 paper, R. Brent Tully presented the conclusions of his research concerning the basic structure of

560-580: The Pavo-Indus Supercluster, and the Fornax Group. The Great Attractor, together with the entire supercluster, is found to be moving toward Shapley Supercluster , with center of Shapley Attractor . The LS has a total mass M ≈ 10 M ☉ and a total optical luminosity L ≈ 3 × 10 L ☉ . This yields a mass-to-light ratio of about 300 times that of the solar ratio ( M ☉ / L ☉ = 1),

588-449: The Triangulum Galaxy, so it may be a satellite of either. The other members of the group are likely gravitationally secluded from these large subgroups: IC 10 , IC 1613 , Phoenix Dwarf Galaxy, Leo A , Tucana Dwarf Galaxy, Cetus Dwarf Galaxy, Pegasus Dwarf Irregular Galaxy , Wolf–Lundmark–Melotte , Aquarius Dwarf Galaxy, and Sagittarius Dwarf Irregular Galaxy . The membership of NGC 3109 , with its companions Sextans A and

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616-489: The case of Laniakea, is called the Great Attractor , and influences the motions of the Local Group of galaxies, where the Milky Way galaxy resides, and all others throughout the supercluster. Unlike its constituent clusters, Laniakea is not gravitationally bound and is projected to be torn apart by dark energy . Although the confirmation of the existence of the Laniakea Supercluster emerged in 2014, early studies in

644-579: The following 11 clouds, given in decreasing order of number of luminous galaxies: Canes Venatici , Virgo Cluster, Virgo II (southern extension), Leo II , Virgo III , Crater ( NGC 3672 ), Leo I , Leo Minor ( NGC 2841 ), Draco ( NGC 5907 ), Antlia ( NGC 2997 ), and NGC 5643 . Of the luminous galaxies located in the disk, one third are in the Virgo Cluster. The remainder are found in the Canes Venatici Cloud and Virgo II Cloud, plus

672-429: The north galactic pole . In the 1950s, French–American astronomer Gérard de Vaucouleurs was the first to argue that this excess represented a large-scale galaxy-like structure, coining the term "Local Supergalaxy" in 1953, which he changed to "Local Supercluster" (LSC) in 1958. Harlow Shapley , in his 1959 book Of Stars and Men , suggested the term Metagalaxy . Debate went on during the 1960s and 1970s as to whether

700-480: The order of 20–60 Mpc in diameter) voids in space. Long filamentary structures seem to predominate. An example of this is the Hydra–Centaurus Supercluster , the nearest supercluster to the Virgo Supercluster, which starts at a distance of roughly 30 Mpc and extends to 60 Mpc. Since the late 1980s it has been apparent that not only the Local Group , but all matter out to a distance of at least 50 Mpc

728-444: The somewhat insignificant NGC 5643 Group . The luminous galaxies in the halo are concentrated in a small number of clouds (94% in 7 clouds). This distribution indicates that "most of the volume of the supergalactic plane is a great void." A helpful analogy that matches the observed distribution is that of soap bubbles. Flattish clusters and superclusters are found at the intersection of bubbles, which are large, roughly spherical (on

756-804: The superclusters and Laniakea were not clearly known at the time of Laniakea's definition. Since then, the study of the edges of the supercluster and of structures beyond them has substantially improved. Laniakea is itself a constituent part of the Pisces–Cetus Supercluster Complex , a galaxy filament . Solar System   → Local Interstellar Cloud   → Local Bubble   → Gould Belt   → Orion Arm   → Milky Way   → Milky Way subgroup   → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster   → Local Hole   → Observable universe   → Universe Each arrow ( → ) may be read as "within" or "part of". * It

784-508: Was suggested by Nawaʻa Napoleon , an associate professor of Hawaiian language at Kapiolani Community College . The name honors Polynesian navigators , who used knowledge of the sky to navigate the Pacific Ocean . The Laniakea Supercluster encompasses approximately 100,000 galaxies stretched out over 160  Mpc (520 million  ly ). It has the approximate mass of 10 solar masses, or 100,000 times that of our galaxy, which

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