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Satellite galaxies of the Milky Way

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The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup. This subgroup is part of the local galaxy cluster, the Local Group.[1]

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.[2] 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.

Characteristics

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 980×10^3 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.[3][4]

List

The Milky Way's satellite galaxies include the following:[5]

Name Diameter (kpc) Distance
(kpc) 		Type Discovered
Canis Major Dwarf 1.5 8 Irr 2003
Sagittarius Dwarf 2 20 E 1994
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
Draco Dwarf 0.7 80 dE0 1954
Sculptor Dwarf 0.8 90 dE3 1937
Sextans Dwarf Spheroidal 0.5 90 dE3 1990
Carina Dwarf Spheroidal 0.5 100 dE3 1977
Ursa Major I Dwarf - 100 dG D 2005
Fornax Dwarf 0.6 140 dE2 1938
Leo II 0.7 210 dE0 1950
Leo I 0.5 250 dE3 1950
Leo IV 0.3 160 dSph 2006
Leo V 0.08 180 dSph 2007
Leo T 0.34 420 dSph/dIrr 2006
Boötes I 0.3 60 dSph 2006
Boötes II 0.1 42 dSph 2007
Boötes III 1 46 dSph? 2009
Coma Berenices 0.14 42 dSph 2006
Segue 2 0.07 35 dSph 2007
Canes Venatici I 2 220 dSph 2006
Canes Venatici II 0.3 155 dSph 2006
Hercules 0.7 135 dSph 2006
Pisces II 0.12 180 dSph 2010
Reticulum II - 30 dSph 2015 [6][7]
Eridanus II - 380 dSph 2015 [6] [7]
Horologium - 100 dSph? 2015 [6] [7] [a]
Pictoris - 115 dSph? 2015 [6] [7] [a]
Phoenix II - 100 dSph? 2015 [6] [7] [a]
Kim 2/Indus I - 100 dSph? 2015 [6] [7] [a]
Grus - 120 dSph 2015 [6]
Eridanus III - 90 dSph? 2015 [6] [7] [a]
Tucana II - 70 dSph 2015 [6] [7]

Clickable map

Milky WaySagittarius Dwarf Elliptical GalaxySextans DwarfLarge Magellanic CloudSmall Magellanic CloudSculptor DwarfFornax DwarfCarina DwarfBootes DwarfUrsa Major IIUrsa Major IUrsa Minor DwarfDraco Dwarf
Milky Way's satellite galaxies (clickable map)

Streams

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.

See also

Footnotes

  1. ^ The distance to edge of the dark matter halo of the galaxy from its center is the virial radius of a galaxy, Rvir
  1. ^ a b c d e May be a globular cluster instead

References

  1. ^ David G. Turner (15 August 2013). "An Eclectic View of our Milky Way Galaxy". Canadian Journal of Physics. 92 (9) (published September 2013): 959–963. arXiv:1310.0014. Bibcode:2014CaJPh..92..959T. doi:10.1139/cjp-2013-0429. {{cite journal}}: Unknown parameter |publicationdate= ignored (|publication-date= suggested) (help)
  2. ^ "Magellanic Clouds May Be Just Passing Through". phys.org. 9 January 2007.
  3. ^ "Milky Way Ransacks Nearby Dwarf Galaxies". SpaceDaily. 17 October 2014.
  4. ^ "Milky Way ransacks nearby dwarf galaxies". ScienceDaily. 15 October 2014.
  5. ^ Nils Sjölander. "Milky Way Satellite Galaxies". Archived from the original on 2014-02-19.
  6. ^ a b c d e f g h i 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. Bibcode:2015arXiv150302079K.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ^ a b c d e f g h DES Collaboration (10 March 2015). "Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data". The Astrophysical Journal. arXiv:1503.02584. Bibcode:2015arXiv150302584T.

Further reading

  • 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. 795 (1) (published 13 October 2014). arXiv:1410.0028. Bibcode:2014arXiv1410.0028S. doi:10.1088/2041-8205/795/1/L5. {{cite journal}}: Unknown parameter |publicationdate= ignored (|publication-date= suggested) (help)CS1 maint: multiple names: authors list (link)



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