List of satellite galaxies of the Milky Way
|This article needs additional citations for verification. (February 2013)|
There are about 30 small galaxies confirmed to be within 420 kiloparsecs (1.4 million light-years) of the Milky Way, though not all of them are necessarily in orbit. Of those, the only ones visible to the naked eye are the Large and Small 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 those galaxies confirmed to be in orbit, the largest is the Sagittarius Dwarf Elliptical Galaxy, which has a diameter of 20,000 light-years (6,100 pc) or roughly a fifth that of the Milky Way.
Satellite galaxies that orbit, from 1,000 ly (310 pc) of the edge of the disc of the Milky Way Galaxy, to the edge of the dark matter halo of the Milky Way at 980×103 ly (300 kpc) from the center of the Galaxy,[note 1] are generally depleted in hydrogen gas compared to those that orbit more distantly. This region is the dense hot gas halo of the Milky Way, which strips cold gas from the satellites. Satellites beyond this region still retain copious quantities of gas.
The Milky Way's satellite galaxies include the following:
|Canis Major Dwarf||1.5||8||Irr||2003|
|Large Magellanic Cloud||4||48.5||SBm||prehistoric|
|Small Magellanic Cloud||2||61||Irr||prehistoric|
|Ursa Major II Dwarf||0.2||30||dG D||2006|
|Ursa Minor Dwarf||0.4||60||dE4||1954|
|Sextans Dwarf Spheroidal||0.5||90||dE3||1990|
|Carina Dwarf Spheroidal||0.5||100||dE3||1977|
|Ursa Major I Dwarf||-||100||dG D||2005|
|Canes Venatici I||2||220||dSph||2006|
|Canes Venatici II||0.3||155||dSph||2006|
|Reticulum II||-||30||dSph||2015 |
|Eridanus II||-||380||dSph||2015  |
|Horologium||-||100||dSph?||2015   [a]|
|Pictoris||-||115||dSph?||2015   [a]|
|Phoenix II||-||100||dSph?||2015   [a]|
|Indus||-||100||dSph?||2015   [a]|
|Eridanus III||-||90||dSph?||2015   [a]|
|Tucana II||-||70||dSph||2015  |
The Sagittarius Dwarf is 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 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.
- The distance to edge of the dark matter halo of the galaxy from its center is the virial radius of a galaxy, Rvir
- May be a globular cluster instead
- David G. Turner (15 August 2013). "An Eclectic View of our Milky Way Galaxy". Canadian Journal of Physics (September 2013) 92 (9): 959–963. arXiv:1310.0014. Bibcode:2014CaJPh..92..959T. doi:10.1139/cjp-2013-0429.
- "Magellanic Clouds May Be Just Passing Through". phys.org. 9 January 2007.
- "Milky Way Ransacks Nearby Dwarf Galaxies". SpaceDaily. 17 October 2014.
- "Milky Way ransacks nearby dwarf galaxies". ScienceDaily. 15 October 2014.
- Nils Sjölander. "Milky Way Satellite Galaxies". Archived from the original on 2014-02-19.
- 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. arXiv:1503.02079.
- DES Collaboration (10 March 2015). "Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data". The Astrophysical Journal. arXiv:1503.02584.
- K. Spekkens, N. Urbancic, B. S. Mason, B. Willman, J. E. Aguirre (30 September 2014). "The Dearth of Neutral Hydrogen in Galactic Dwarf Spheroidal Galaxies". The Astrophysical Journal Letters (13 October 2014) 795 (1). arXiv:1410.0028. Bibcode:2014arXiv1410.0028S. doi:10.1088/2041-8205/795/1/L5.
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