The
Milky Way has several smaller
galaxies gravitationally bound to it, as part of the Milky Way
subgroup, which is part of the local galaxy cluster, the
Local Group.
There are 59 small galaxies confirmed to be within of the Milky Way, but not all of them are necessarily in orbit, and some may themselves be in orbit of other satellite galaxies. The only ones visible to the naked eye are the
Large and
Small
Small may refer to:
Science and technology
* SMALL, an ALGOL-like programming language
* Small (anatomy), the lumbar region of the back
* ''Small'' (journal), a nano-science publication
* <small>, an HTML element that defines smaller text ...
Magellanic Clouds, which have been observed since prehistory. Measurements with the Hubble Space Telescope in 2006 suggest the Magellanic Clouds may be moving too fast to be orbiting the Milky Way. Of the galaxies confirmed to be in orbit, the largest is the
Sagittarius Dwarf Elliptical Galaxy, which has a diameter of
or roughly a twentieth that of the Milky Way.
Characteristics
Satellite galaxies that orbit from of the edge of the
disc of the Milky Way Galaxy to the edge of the
dark matter halo
According to modern models of physical cosmology, a dark matter halo is a basic unit of cosmological structure. It is a hypothetical region that has decoupled from cosmic expansion and contains gravitationally bound matter.
A single dark matte ...
of the Milky Way at from the center of the galaxy, are generally depleted in hydrogen gas compared to those that orbit more distantly. This is because of their interactions with the dense hot gas halo of the Milky Way that strip cold gas from the satellites. Satellites beyond that region still retain copious quantities of gas.
List
The Milky Way's satellite galaxies include the following:
Map with clickable regions
Image:Satellite_Galaxies.svg, 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
The Sextans Dwarf Spheroidal is a dwarf spheroidal galaxy that was discovered in 1990 by Mike Irwin as the 8th satellite of the Milky Way, located in the constellation of Sextans. It is also an elliptical galaxy, and displays a redshift because ...
rect 168 273 249 318 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 ...
rect 229 326 288 368 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 ...
rect 297 376 352 407 Sculptor Dwarf
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 ...
rect 183 446 234 476 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 ...
rect 107 297 150 332 Carina Dwarf
rect 296 107 339 144 Bootes Dwarf
rect 336 180 408 196 Ursa Major II
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 ...
rect 357 40 423 59 Ursa Major I
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 ...
rect 370 110 428 142 Ursa Minor Dwarf
rect 430 119 470 154 Draco Dwarf
The Draco Dwarf is a spheroidal galaxy which was discovered by Albert George Wilson of Lowell Observatory in 1954 on photographic plates of the National Geographic Society's Palomar Observatory Sky Survey (POSS). It is part of the Local Group a ...
desc bottom-left
Streams
The Sagittarius Dwarf Spheroidal Galaxy is currently in the process of being
consumed by the Milky Way and is expected to pass through it within the next 100 million years. The
Sagittarius Stream
In astronomy, the Sagittarius Stream is a long, complex structure made of stars that wrap around the Milky Way galaxy in an orbit that nearly crosses the galactic poles. It consists of Tidal stripping, tidally stripped stars from the Sagittarius Dw ...
is a stream of stars in polar orbit around the Milky Way leeched from the Sagittarius Dwarf. The
Virgo Stellar Stream is a stream of stars that is believed to have once been an orbiting dwarf galaxy that has been completely distended by the Milky Way's gravity.
See also
*
List of Andromeda's satellite galaxies
The Andromeda Galaxy (M31) has satellite galaxies just like the Milky Way. Orbiting M31 are at least 13 dwarf galaxies: the brightest and largest is M110, which can be seen with a basic telescope. The second-brightest and closest one to M31 is ...
*
List of nearest galaxies
*
Local Group
Notes
References
Further reading
*
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*
Local Group