Local Group of galaxies, including the massive members Messier 31 (Andromeda Galaxy) and Milky Way, as well as other nearby galaxies.
Observation data (Epoch J2000)
Parent structure
Virgo Supercluster
See also: Galaxy group, Galaxy cluster, List of galaxy groups and clusters
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; 9×1019 kilometres),[1] and a total mass of the order of 2×1012 solar masses (4×1042 kg).[2]
It consists of two collections of galaxies in 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 (3×10^6 ly; 2×1019 km) and are moving toward one another with a velocity of 123 km/s.[3] 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 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 1012 solar masses each. Each has its own system of satellite galaxies:
The Andromeda Galaxy's satellite system consists of Messier 32 (M32), Messier 110 (M110), NGC 147, NGC 185, Andromeda I (And I), And II, And III, And V, And VI (also known as the Pegasus Dwarf Spheroidal Galaxy, or Pegasus dSph), And VII (a.k.a. the Cassiopeia Dwarf Galaxy), And VIII, And IX, And X, And XI, And XIX, And XXI and And XXII, plus several additional ultra-faint dwarf spheroidal galaxies.[4]
The Milky Way's satellite galaxies system comprises the Sagittarius Dwarf Galaxy, Large Magellanic Cloud, Small Magellanic Cloud, Canis Major Dwarf Galaxy (disputed, considered by some not a galaxy), Ursa Minor Dwarf Galaxy, Draco Dwarf Galaxy, Carina Dwarf Galaxy, Sextans Dwarf Galaxy, Sculptor Dwarf Galaxy, Fornax Dwarf Galaxy, Leo I (a dwarf galaxy), Leo II (a dwarf galaxy), Ursa Major I Dwarf Galaxy and Ursa Major II Dwarf Galaxy, plus several additional ultra-faint dwarf spheroidal galaxies.[5]
The Triangulum Galaxy (M33) is the third-largest member of the Local Group, with a mass of approximately 5×1010M☉ (1×1041 kg), and is the third spiral galaxy.[6] It is unclear whether the Triangulum Galaxy is a companion of the Andromeda Galaxy; the two galaxies are 750,000 light years apart,[7] 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 the Triangulum Galaxy, so it may be a satellite of either.[8]
The membership of NGC 3109, with its companions Sextans A and the Antlia Dwarf Galaxy, is uncertain due to extreme distances from the center of the Local Group.[3]
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.[9]
^Redd, Nola Taylor (18 December 2017). "Astronomers track dwarf galaxies to better understand the Milky Way's make-up and evolution". Proceedings of the National Academy of Sciences. 115 (51): 12836–12838. doi:10.1073/pnas.1817136115. PMC 6304947. PMID 30568025. S2CID 58645004.
^The mass of the Local Group is essentially accounted for by the mass of the Milky Way and the Andromeda Galaxy.
Estimates for the mass of each galaxy are compatible with 1012M☉,
and Peñarrubia et al. (2014) estimate (2.3±0.7)×1012M☉ for the Local Group,
but Karachentsev and Kashibadze (2006) estimate the somewhat lower value of (1.29±0.14)×1012M☉.
^ abKarachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6. S2CID 120973010.
^Kalirai, Jason S.; Beaton, Rachael L.; Geha, Marla C.; Gilbert, Karoline M.; Guhathakurta, Puragra; Kirby, Evan N.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J. (17 February 2010). "The Splash Survey: Internal Kinematics, Chemical Abundances, and Masses of the Andromeda I, Ii, III, Vii, X, and Xiv Dwarf Spheroidal Galaxies". The Astrophysical Journal. 711 (2): 671–692. arXiv:0911.1998. Bibcode:2010ApJ...711..671K. doi:10.1088/0004-637X/711/2/671. ISSN 0004-637X. S2CID 43188686.
^Sergey E. Koposov; Vasily Belokurov; Gabriel Torrealba; N. Wyn Evans (10 March 2015). "Beasts of the Southern Wild. Discovery of a large number of Ultra Faint satellites in the vicinity of the Magellanic Clouds". The Astrophysical Journal. 805 (2): 130. arXiv:1503.02079. Bibcode:2015ApJ...805..130K. doi:10.1088/0004-637X/805/2/130. S2CID 118267222.
^"The Local Group". NASA's High Energy Astrophysics Science Archive Research Center (HEASARC). NASA. Retrieved 5 May 2015.
^"Messier Object 33". www.messier.seds.org. Retrieved 21 May 2021.
^Miller, Bryan W.; et al. (December 2001). "The Star Formation History of LGS 3". The Astrophysical Journal. 562 (2): 713–726. arXiv:astro-ph/0108408. Bibcode:2001ApJ...562..713M. doi:10.1086/323853. ISSN 0004-637X. S2CID 119089499.
^McConnachie, Alan W. (2012). "The observed properties of dwarf galaxies in and around the Local Group". The Astronomical Journal. 144 (1): 4. arXiv:1204.1562. Bibcode:2012AJ....144....4M. doi:10.1088/0004-6256/144/1/4. S2CID 118515618.
The LocalGroup is the galaxy group that includes the Milky Way, where Earth is located. It has a total diameter of roughly 3 megaparsecs (10 million...
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The Local Sheet in astronomy is a nearby extragalactic region of space where the Milky Way, the members of the LocalGroup and other galaxies share a similar...
other voids, it is not completely empty but contains the Milky Way, the LocalGroup, and the larger part of the Laniakea Supercluster. The Milky Way is within...
(Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies containing the Virgo Cluster and LocalGroup, which itself contains...
kpc). The Milky Way has several satellite galaxies and is part of the LocalGroup of galaxies, which form part of the Virgo Supercluster, which is itself...
The Local Void is a vast, empty region of space, lying adjacent to the LocalGroup. Discovered by Brent Tully and Rick Fisher in 1987, the Local Void is...
system itself, do not change under local transformations according to certain smooth families of operations (Lie groups). Formally, the Lagrangian is invariant...
about 50 major LocalGroup galaxies, and some that are members of neighboring galaxy groups, the M81 Group and the Centaurus A/M83 Group, and some that...
have sex′, called by other groups, because they preferred to marry endogamy and chose their partners from their own localgroup; this was viewed critically...
into groups, clusters and superclusters. The Milky Way is part of the LocalGroup, which it dominates along with the Andromeda Galaxy. The group is part...
superclusters of galaxies. The Milky Way galaxy is part of a group of galaxies called the LocalGroup. Groups of galaxies are the smallest aggregates of galaxies...
Sculptor Group is a loose group of galaxies visible near the south galactic pole. The group is one of the closest groups of galaxies to the LocalGroup; the...
Chihuahua, eastern localgroup) Hakaye localgroup (were part of Sierra Madre Mountains of Sonora Mexico) Carrizaleños localgroup (known by other Chiricahua...
contains the Leo Ring. The group is one of many groups that lies within the Virgo Supercluster (the combined LocalGroup and Virgo cluster). The table...
not a local field. For example, its residue field is C[[T]]/(T) = C, which is not finite. The nth higher unit group of a non-Archimedean local field F...
approximate center of the group is located at a distance of 3.6 Mpc, making it one of the nearest groups to the LocalGroup. The group is estimated to have...
large group of smaller galaxy clusters or galaxy groups; they are among the largest known structures in the universe. The Milky Way is part of the Local Group...
about 51 galaxies in the LocalGroup (see list of nearest galaxies for a complete list), on the order of 100,000 in the Local Supercluster, and an estimated...
Laniakea, is called the Great Attractor, and influences the motions of the LocalGroup of galaxies, where the Milky Way galaxy resides, and all others throughout...
Local government is a generic term for the lowest tiers of governance or public administration within a particular sovereign state. Local governments...
its campus groups "charges" instead of chapters. Where a national fraternity absorbs a pre-existing localgroup, it may allow the localgroup to keep its...