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 ...

" 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 gal ...

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 so ...

. The two largest members, the Andromeda Galaxy and the Milky Way, are both spiral galaxies with masses of about solar masses each. Each has its own system of satellite galaxies: * 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 Genti ...

(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 depicte ...

(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 (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, Small Magellanic Cloud, Canis Major Dwarf Galaxy (disputed, considered by some not a galaxy), Ursa Minor Dwarf 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, Fornax Dwarf Galaxy, Leo I (a dwarf galaxy), Leo II (a dwarf galaxy), Ursa Major I Dwarf 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 (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 Galaxy is equidistant from the Andromeda Galaxy and the Triangulum Galaxy, so it may be a satellite of either. The membership of NGC 3109, 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 1613, Phoenix Dwarf Galaxy, Leo A,

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.

History

The term "The Local Group" was introduced by Edwin Hubble 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, Large Magellanic Cloud, Small Magellanic Cloud, 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 ...

, NGC 185, IC 1613 and NGC 147. He also identified IC 10 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 rect 155 17 215 35 Sextans B circle 130 37 10

rect 95 25 155 45

circle 100 144 5 NGC 3109 rect 65 130 100 160 NGC 3109 circle 109 149 5

rect 109 146 145 175

circle 314 119 5 Leo A rect 280 97 340 125 Leo A 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 Phoenix Dwarf rect 275 325 335 375 Phoenix Dwarf 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 IC 1613 rect 390 373 420 400 IC 1613 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 Triangulum Galaxy rect 400 321 480 340 Triangulum Galaxy circle 417 254 15 NGC 185 rect 440 185 480 211 NGC 185 rect 432 237 447 260 NGC 147 rect 480 195 508 225 NGC 147 poly 450 264 434 265 431 280 442 280 M110 rect 508 205 540 225 M110 circle 461 229 17 IC 10 rect 493 241 525 256 IC 10 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 and Small Magellanic Clouds over 100° through the Galactic south pole of the Milky Way. The stream contains a gaseous feature dubbed the ''leading arm''. ...

, 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