The Local Group is the

galaxy group A galaxy group or group of galaxies (GrG) is an aggregation of galaxies comprising about 50 or fewer gravitationally bound members, each at least as luminous as the Milky Way (about 1010 times the luminosity of the Sun); collections of galaxie ...

that includes the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

. It has a total diameter of roughly , and a total mass of the order of . It consists of two collections of galaxies in a "

dumbbell The dumbbell, a type of free weight, is a piece of equipment used in weight training. It can be used individually or in pairs, with one in each hand. History The forerunner of the dumbbell, halteres, were used in ancient Greece as lifting w ...

" shape: the Milky Way and its satellites form one lobe, and the

Andromeda Galaxy The Andromeda Galaxy (IPA: ), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about approximately from Earth and the nearest large galaxy to the Milky Way. The gala ...

and its satellites constitute the other. The two collections are separated by about and are moving toward one another with a velocity of . The group itself is a part of the larger

Virgo Supercluster The Virgo Supercluster (Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which itself contains the Milky Way and Andromeda galaxies, as well as others. At least ...

, which may be a part of the

Laniakea Supercluster The Laniakea Supercluster (; Hawaiian for "open skies" or "immense heaven") 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 astronom ...

. 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 A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is s ...

. The two largest members, the Andromeda Galaxy and the Milky Way, are both

spiral galaxies Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es each. Each has its own system of

satellite galaxies A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy (also known as the primary galaxy). Satellite galaxies and their constituents are bound ...

: * The Andromeda Galaxy's satellite system consists of

Messier 32 Messier 32 (also known as M32 and NGC 221) is a dwarf "early-type" galaxy about from the Solar System, appearing in the constellation Andromeda. M32 is a satellite galaxy of the Andromeda Galaxy (M31) and was discovered by Guillaume Le Gentil ...

(M32),

Messier 110 Messier 110, or M110, also known as NGC 205, is a dwarf elliptical galaxy that is a satellite of the Andromeda Galaxy in the Local Group. Early observational history Charles Messier never included the galaxy in his list, but it was depicted ...

(M110),

NGC 147 NGC 147 (also known as DDO3 or Caldwell 17) is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. NGC 147 is a member of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It forms a ...

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 ...

, 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 (also known as 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. * The Milky Way's satellite galaxies system comprises the Sagittarius Dwarf Galaxy,

Large Magellanic Cloud The Large Magellanic Cloud (LMC), or Nubecula Major, is a satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (≈160,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the ...

Small Magellanic Cloud The Small Magellanic Cloud (SMC), or Nubecula Minor, is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a D25 isophotal diameter of about , and contains several hundred million stars. It has a total mass of ...

Canis Major Dwarf Galaxy The Canis Major Overdensity (''CMa Overdensity'') or Canis Major Dwarf Galaxy (''CMa Dwarf'') is a disputed dwarf irregular galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major. The supposed small gal ...

(disputed, considered by some not a galaxy),

Ursa Minor Dwarf The Ursa Minor Dwarf is a dwarf spheroidal galaxy, discovered by A.G. Wilson of the Lowell Observatory, in the United States, during the Palomar Sky Survey in 1955. It appears in the Ursa Minor constellation, and is a satellite galaxy of the Mi ...

Galaxy, Draco Dwarf Galaxy,

Carina Dwarf The Carina Dwarf Spheroidal Galaxy is a dwarf galaxy in the Carina constellation. It was discovered in 1977 with the UK Schmidt Telescope The UK Schmidt Telescope (UKST) is a 1.24 metre Schmidt telescope operated by the Australian Ast ...

Galaxy, Sextans Dwarf Galaxy,

Sculptor Dwarf Galaxy The Sculptor Dwarf Galaxy (also known as Sculptor Dwarf Elliptical Galaxy or the Sculptor Dwarf Spheroidal Galaxy, and formerly as the Sculptor System) is a dwarf spheroidal galaxy that is a satellite of the Milky Way. The galaxy lies within the ...

Fornax Dwarf The Fornax Dwarf Spheroidal (formerly known as the Fornax System) is an elliptical dwarf galaxy in the constellation Fornax that was discovered in 1938 by Harlow Shapley. He discovered it while he was in South Africa on photographic plates take ...

Galaxy,

Leo I The LEO I (Lyons Electronic Office I) was the first computer used for commercial business applications. The prototype LEO I was modelled closely on the Cambridge EDSAC. Its construction was overseen by Oliver Standingford, Raymond Thompson and ...

(a dwarf galaxy), Leo II (a dwarf galaxy),

Ursa Major I Dwarf Ursa Major I Dwarf (UMa I dSph) is a dwarf spheroidal galaxy that orbits the Milky Way galaxy. It was discovered in 2005 within the Ursa Major constellation and is the third least luminous known galaxy. Discovery It was discovered by Beth Willm ...

Galaxy and

Ursa Major II Dwarf Ursa Major II Dwarf (UMa II dSph) is a dwarf spheroidal galaxy situated in the Ursa Major constellation and discovered in 2006 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located approximately 30 kpc from the Sun and ...

Galaxy, plus several additional ultra-faint dwarf spheroidal galaxies. Local Group Galaxies Comparison

The

Triangulum Galaxy The Triangulum Galaxy is a spiral galaxy 2.73 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC (''New General Catalogue)'' 598. With the D25 isophotal diameter of , the Triangulum Ga ...

(M33) is the third-largest member of the Local Group, with a mass of approximately , 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 The Pisces Dwarf, also known as Pisces I, is an irregular dwarf galaxy that is part of the Local Group. The galaxy, taking its name from the constellation Pisces where it appears, is suspected of being a satellite galaxy of the Triangulum Gal ...

Galaxy is equidistant from the Andromeda Galaxy and the Triangulum Galaxy, so it may be a satellite of either. The membership of

NGC 3109 NGC 3109 is a small barred Magellanic type spiral or irregular galaxy around 4.34 Mly away in the direction of the constellation of Hydra. NGC 3109 is believed to be tidally interacting with the dwarf elliptical galaxy Antlia Dwarf. It was di ...

, with its companions

Sextans A Sextans A (also known as UGCA 205) is a small dwarf irregular galaxy. It spans about 5000 light-years across, and is located at 4.3 million light-years away, in the outskirts of the Local Group of galaxies, which includes the Milky Way galaxy, an ...

and the

Antlia Dwarf The Antlia Dwarf is a dwarf spheroidal/ irregular galaxy. It lies about 1.3 Mpc (4.3 million light-years) from Earth in the constellation Antlia. It is the fourth and faintest member of the nearby Antlia-Sextans Group of galaxies. The ga ...

Galaxy, is uncertain due to extreme distances from the center of the Local Group. The other members of the group are likely gravitationally secluded from these large subgroups:

IC 10 IC 10 is an irregular galaxy in the constellation Cassiopeia. It was discovered by Lewis Swift in 1887 and in 1935 Nicholas Mayall became the first to suggest that the object is extragalactic. Edwin Hubble suspected it might belong to the Loc ...

IC 1613 IC 1613 (object 1613 in the Index Catalogues (IC), also known as Caldwell 51) is an irregular dwarf galaxy, visible in the constellation Cetus near the star 26 Ceti. It was discovered in 1906 by Max Wolf, and is approaching Earth at 234 ...

Phoenix Dwarf The Phoenix Dwarf is a dwarf irregular galaxy discovered in 1976 by Hans-Emil Schuster and Richard Martin West and mistaken for a globular cluster. It is currently 1.44 Mly away from Earth Earth is the third planet from the Sun ...

Galaxy,

Leo A Leo A (also known as Leo III) is an irregular galaxy that is part of the Local Group. It lies 2.6 million light-years from Earth, and was discovered by Fritz Zwicky in 1942. The estimated mass of this galaxy is solar masses, with at least 80 ...

Tucana Dwarf The Tucana Dwarf Galaxy is a dwarf galaxy in the constellation Tucana. It was discovered in 1990 by R.J. Lavery of Mount Stromlo Observatory. It is composed of very old stars and is very isolated from other galaxies. Its location on the opposite ...

Galaxy, Cetus Dwarf Galaxy,

Pegasus Dwarf Irregular Galaxy The Pegasus Dwarf Irregular Galaxy (also known as Peg DIG or the Pegasus Dwarf) is a dwarf irregular galaxy in the direction of the constellation Pegasus. It was discovered by A. G. Wilson in the 1950s. The Pegasus Dwarf is a companion of the A ...

, Wolf–Lundmark–Melotte,

Aquarius Dwarf The Aquarius Dwarf is a dwarf irregular galaxy, first catalogued in 1959 by the DDO survey. It is located within the boundaries of the constellation of Aquarius. It is a member of the Local Group of galaxies, albeit an extremely isolated one; ...

Galaxy, and

Sagittarius Dwarf Irregular Galaxy The Sagittarius Dwarf Irregular Galaxy (SagDIG) is a dwarf galaxy in the constellation of Sagittarius. (SagDIG should not be confused with the Sagittarius Dwarf Spheroidal Galaxy, SagDEG, a satellite galaxy of the Milky Way discovered decades ...

History

The term "The Local Group" was introduced by

Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an Americans, American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology. Hubble proved that many objects ...

in Chapter VI of his 1936 book ''The Realm of the Nebulae''.Alt URL
pp. 124–151) There, he described it as "a typical small group of nebulae which is isolated in the general field" and delineated, by decreasing luminosity, its members to be M31,

, M33,

, M32, NGC 205,

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. Barna ...

and

. He also identified

as a possible part of the Local Group.

Component galaxies

Map

Image:Local_Group.svg, frame, center, Local Group (clickable map) rect 392 53 405 72 ly circle 318 239 20

rect 345 256 375 284

circle 383 310 5

rect 348 292 380 322

circle 177 27 10

Sextans B Sextans B (also known as UGC 5373 and DDO 70) is an irregular galaxy that may be part of the Local Group, or lie just beyond it. Sextans B is 4.44 million light-years away from Earth and thus is one of the most distant members of the Local Gro ...

rect 155 17 215 35

circle 130 37 10

rect 95 25 155 45

circle 100 144 5

rect 65 130 100 160

circle 109 149 5

rect 109 146 145 175

circle 314 119 5

rect 280 97 340 125

circle 315 210 5 Leo I (dwarf galaxy) rect 280 180 315 205 Leo I (dwarf galaxy) rect 320 180 335 220 Leo II (dwarf galaxy) circle 349 213 5 Canes Dwarf rect 350 195 400 223 Canes Dwarf circle 310 350 15

rect 275 325 335 375

circle 265 415 15

rect 215 395 275 445

circle 392 445 5 Wolf-Lundmark-Melotte rect 360 435 392 455 Wolf-Lundmark-Melotte circle 370 410 5 Cetus Dwarf rect 345 395 390 430 Cetus Dwarf circle 395 373 10

rect 390 373 420 400

rect 381 335 393 357

SagDIG The Sagittarius Dwarf Irregular Galaxy (SagDIG) is a dwarf galaxy in the constellation of Sagittarius. (SagDIG should not be confused with the Sagittarius Dwarf Spheroidal Galaxy, SagDEG, a satellite galaxy of the Milky Way discovered decades ...

rect 430 450 480 475

rect 393 335 406 356

rect 450 425 510 450

circle 412 332 12

LGS 3 The Pisces Dwarf, also known as Pisces I, is an irregular dwarf galaxy that is part of the Local Group. The galaxy, taking its name from the constellation Pisces where it appears, is suspected of being a satellite galaxy of the Triangulum Ga ...

rect 465 405 510 425

circle 460 361 21 Pegasus Dwarf rect 485 370 540 405 Pegasus Dwarf poly 440 282 455 260 511 259 493 285

rect 484 280 550 305

circle 417 304 2

rect 400 321 480 340

circle 417 254 15

rect 440 185 480 211

rect 432 237 447 260

rect 480 195 508 225

poly 450 264 434 265 431 280 442 280 M110 rect 508 205 540 225 M110 circle 461 229 17

rect 493 241 525 256

rect 524 305 550 323 M32 circle 394 272 14 Andromeda II rect 500 345 515 360 Andromeda II rect 427 279 438 294 Andromeda III rect 518 345 530 360 Andromeda III rect 438 282 450 294 Andromeda I rect 557 345 570 360 Andromeda I desc bottom-left

List

Other objects

Magellanic Stream The Magellanic Stream is a stream of high-velocity clouds of gas extending from the Large Magellanic Cloud, Large and Small Magellanic Clouds over 100° through the Galactic south pole of the Milky Way. The stream contains a gaseous feature dubb ...

, a stream of gas being stripped off the Magellanic Clouds due to their interaction with the Milky Way *

Monoceros Ring The Monoceros Ring ''(monoceros: Greek for 'unicorn')'' is a long, complex, ring of stars that wraps around the Milky Way three times. This is proposed to consist of a stellar stream torn from the Canis Major Dwarf Galaxy by tidal forces as part ...

, a ring of stars around the Milky Way that is proposed to consist of a

stellar stream In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as t ...

torn from the Canis Major Dwarf Galaxy

References

External links

* * * {{Authority control Galaxy clusters Virgo Supercluster