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Local Group
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The Local Group is the group of galaxies that includes our galaxy, the Milky Way. The group comprises over 50 galaxies (including dwarf galaxies), with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy. The galaxies of the Local Group cover a 10 million light-year diameter (see 1 E+22 m for distance comparisons) and have a binary (dumbbell) shape.

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Encyclopedia
The Local Group is the group of galaxies that includes our galaxy, the Milky Way. The group comprises over 50 galaxies (including dwarf galaxies), with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy. The galaxies of the Local Group cover a 10 million light-year diameter (see 1 E+22 m for distance comparisons) and have a binary (dumbbell) shape. The group is estimated to have a total mass of (1.29 ± 0.14)M?.
The group itself is one of many within the Virgo Supercluster (i.e. the Local Supercluster).
The two most massive members of the group are the Milky Way and the Andromeda Galaxy. These two Spiral Galaxies each have a system of satellite galaxies.
- The Milky Way's satellite system consists of Sagittarius Dwarf Galaxy, Large Magellanic Cloud, Small Magellanic Cloud, Canis Major Dwarf, Ursa Minor Dwarf, Draco Dwarf, Carina Dwarf, Sextans Dwarf, Sculptor Dwarf, Fornax Dwarf, Leo I, Leo II, and Ursa Major Dwarf.
- Andromeda's satellite system comprises M32, M110, NGC 147, NGC 185, And I, And II, And III, And IV, And V, Pegasus dSph, Cassiopeia Dwarf, And VIII, And IX, and And X.
- The Triangulum Galaxy, the third largest and only ordinary spiral galaxy in the Local Group, may or may not be a companion to the Andromeda galaxy but probably has Pisces Dwarf as a satellite.
The other members of the group are gravitationally secluded from these large subgroups: IC10, IC1613, Phoenix Dwarf, Leo A, Tucana Dwarf, Cetus Dwarf, Pegasus Dwarf Irregular, Wolf-Lundmark-Melotte, Aquarius Dwarf, and Sagittarius Dwarf Irregular.
History
Edwin Hubble was the first to identify the Local Group in Chapter VI of his book The Realm of Nebulae (Hubble 1936, pp. 124–151). There he describes it as "a typical small group of nebulae which is isolated in the general field." In that book, he delineated by decreasing luminosity its members to be M31, the Milky Way, M33, the Large Magellanic Cloud, the Small Magellanic Cloud, M32, NGC 205, NGC 6822, NGC 185, IC 1613 and NGC 147. He also identified IC 10 as a possible Local Group member. In the ~70 years since his work, the number of known Local Group members has increased from his initial twelve to thirty-six as of 2003, by way of the discovery of almost two dozen low-luminosity galaxies.
Component galaxies
Clickable maps
Image:Local_Group.JPG|frame|center|Local group (clickable map)
circle 167 27 20 Sextans B
circle 120 36 23 Sextans A
circle 318 239 20 Milky Way
circle 289 197 16 Leo I (dwarf galaxy)
circle 334 201 15 Canes Dwarf
rect 303 185 318 215 Leo II (dwarf galaxy)
circle 357 289 28 NGC 6822
circle 288 323 24 Phoenix Dwarf
circle 248 391 35 Tucana Dwarf
circle 363 416 20 Wolf-Lundmark-Melotte
circle 363 383 17 Cetus Dwarf
circle 369 346 11 IC 1613
rect 381 335 393 357 SagDIG
rect 393 335 406 356 Aquarius Dwarf
circle 417 304 17 Triangulum Galaxy
circle 417 254 15 NGC 185
rect 432 237 447 260 NGC 147
circle 461 229 17 IC 10
poly 440 282 455 260 511 259 493 285 Andromeda Galaxy
poly 450 264 434 265 431 280 442 280 Messier 110
circle 295 110 20 Leo A
circle 84 128 20 NGC 3109
circle 109 149 14 Antlia Dwarf
circle 412 332 12 LGS 3
circle 460 361 21 Pegasus Dwarf
circle 394 272 14 Andromeda II
rect 427 279 438 294 Andromeda III
rect 438 282 450 294 Andromeda I
desc bottom-left
Image:Satellite_Galaxies.JPG|frame|center|Milky Way's satellite galaxies (clickable map)
rect 289 219 352 251 Milky Way
rect 319 252 380 281 Sagittarius Dwarf Elliptical Galaxy
rect 187 81 229 113 Sextans Dwarf
rect 168 273 249 318 Large Magellanic Cloud
rect 229 326 288 368 Small Magellanic Cloud
rect 297 376 352 407 Sculptor Dwarf
rect 183 446 234 476 Fornax Dwarf
rect 107 297 150 332 Carina Dwarf
rect 296 107 339 144 Bootes Dwarf
rect 336 180 408 196 Ursa Major II
rect 357 40 423 59 Ursa Major I
rect 370 110 428 142 Ursa Minor Dwarf
rect 430 119 470 154 Draco Dwarf
desc bottom-left
Galactic bodies
Other notable objects
- Smith's Cloud - High velocity cloud, between 32,000 and 49,000 light years from Earth, and 8000 light years from the disk of the Milky Way Galaxy.
- HVC 127-41-330 - High velocity cloud, 2.3 million light-years from Earth
See also
External links
- , SEDS Messier pages
- , Lowell Observatory
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