Satellite galaxies of the Milky Way

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.[1]

There are about 50 small galaxies confirmed to be within 420 kiloparsecs (1.4 million light-years) 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 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 the galaxies confirmed to be in orbit, the largest is the Sagittarius Dwarf Elliptical Galaxy, which has a diameter of 2.6 kiloparsecs (8,500 ly)[3] 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. The reason is the dense hot gas halo of the Milky Way, which strips cold gas from the satellites. Satellites beyond that region still retain copious quantities of gas.[4][5]

List

The Milky Way's satellite galaxies include the following:[6]

Name Diameter (kpc) Distance
(kpc)		 Absolute magnitude Type Discovered
Canis Major Dwarf 1.5 8 Irr 2003
Sagittarius Dwarf 2.6 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 1 0.06 23 -3.0 dSph 2007
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 I 80 dSph? 2009
Pisces II 0.12 180 dSph 2010
Crater/Laevens I 0.06 145 GC[7] 2014 [8][9]
Reticulum II - 30 dSph 2015 [10][11]
Eridanus II [12] 0.55 366 -7.1 dSph 2015 [10][11]
Horologium I - 100 dSph? 2015 [10][11] [lower-alpha 1]
Pictoris - 115 dSph? 2015 [10][11] [lower-alpha 1]
Phoenix II - 100 dSph? 2015 [10][11] [lower-alpha 1]
Kim 2/Indus I - 100 GC 2015 [10][11]
Grus I - 120 dSph 2015 [10]
Eridanus III - 90 dSph? 2015 [10][11] [lower-alpha 1]
Tucana II - 70 dSph 2015 [10][11]
Triangulum II 0.07 30 -1.8 dSph 2015
Hydra II 0.14 128 dSph 2015 [13]
Pegasus III 0.11 215 -3.4 dSph 2015 [14][15]
Grus II 0.19 53 dSph 2015 [16]
Tucana III 0.09 25 dSph 2015 [16]
Columba I 0.21 182 dSph 2015 [16]
Tucana IV 0.25 48 dSph 2015 [16]
Reticulum III 0.13 92 dSph 2015 [16]
Tucana V 0.03 55 dSph 2015 [16]
Indus II 0.36 214 dSph? 2015 [16]
Cetus II 0.03 30 dSph? 2015 [16]
Horologium II 0.09 78 dSph 2015 [17]
Draco II 0.04 20 -2.9 dSph 2015 [18]
Sagittarius II 0.08 67 -5.2 dSph 2015 [18]
DES - 82 GC 2016 [19]
Crater II 2.2 117.5 dSph 2016 [20]
Aquarius II 0.32 108 -4.2 dSph 2016 [21]

Clickable map

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 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. 1 2 3 4 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 (published September 2013). 92 (9): 959–963. arXiv:1310.0014Freely accessible. Bibcode:2014CaJPh..92..959T. doi:10.1139/cjp-2013-0429.
  2. ↑ "Magellanic Clouds May Be Just Passing Through". phys.org. 9 January 2007.
  3. ↑ Karachentsev, I. D.; Karachentseva, V. E.; Hutchmeier, W. K.; Makarov, D. I. (2004). "A Catalog of Neighboring Galaxies". The Astronomical Journal. 127 (4): 2031–2068. Bibcode:2004AJ....127.2031K. doi:10.1086/382905.
  4. ↑ "Milky Way Ransacks Nearby Dwarf Galaxies". SpaceDaily. 17 October 2014.
  5. ↑ "Milky Way ransacks nearby dwarf galaxies". ScienceDaily. 15 October 2014.
  6. ↑ Nils Sjölander. "Milky Way Satellite Galaxies". Archived from the original on 2014-02-19.
  7. ↑ Voggel, Karina; Hilker, Michael; Baumgardt, Holger; Collins, Michelle L.M.; Grebel, Eva K.; Husemann, Bernd; Richtler, Tom; Frank, Matthias J. "Probing the boundary between star clusters and dwarf galaxies: A MUSE view on the dynamics of Crater/Laevens I". arXiv:1604.06806Freely accessible [astro-ph].
  8. ↑ Benjamin P. M. Laevens; et al. (8 April 2014). "A NEW DISTANT MILKY WAY GLOBULAR CLUSTER IN THE PAN-STARRS1 3π SURVEY". The Astrophysical Journal Letters. 786 (1): L3. arXiv:1403.6593Freely accessible. Bibcode:2014ApJ...786L...3L. doi:10.1088/2041-8205/786/1/L3.
  9. ↑ V. Belokurov, M. J. Irwin, S. E. Koposov, N. W. Evans, E. Gonzalez-Solares, N. Metcalfe and T. Shanks (1 July 2014). "ATLAS lifts the Cup: discovery of a new Milky Way satellite in Crater". Monthly Notices of the Royal Astronomical Society. 441 (3): 2124–2133. arXiv:1403.3406Freely accessible. Bibcode:2014MNRAS.441.2124B. doi:10.1093/mnras/stu626.
  10. 1 2 3 4 5 6 7 8 9 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. 805: 130. arXiv:1503.02079Freely accessible. Bibcode:2015ApJ...805..130K. doi:10.1088/0004-637X/805/2/130.
  11. 1 2 3 4 5 6 7 8 DES Collaboration (10 March 2015). "Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data". The Astrophysical Journal. 807: 50. arXiv:1503.02584Freely accessible. Bibcode:2015ApJ...807...50B. doi:10.1088/0004-637X/807/1/50.
  12. ↑ Crnojević, D.; Sand, D. J.; Zaritsky, D.; Spekkens, K.; Willman, B.; Hargis, J. R. "DEEP IMAGING OF ERIDANUS II AND ITS LONE STAR CLUSTER". arXiv:1604.08590Freely accessible [astro-ph].
  13. ↑ Martin, Nicolas F.; et al. (Survey of the Magellanic Stellar History) (23 April 2015). "HYDRA II: A FAINT AND COMPACT MILKY WAY DWARF GALAXY FOUND IN THE SURVEY OF THE MAGELLANIC STELLAR HISTORY". The Astrophysical Journal Letters. 804 (1): L5. arXiv:1503.06216Freely accessible. Bibcode:2015ApJ...804L...5M. doi:10.1088/2041-8205/804/1/L5.
  14. ↑ Kim, Dongwon; Jerjen, Helmut; Mackey, Dougal; Da Costa, Gary S.; Milone, Antonino P. (12 May 2015). "A HERO'S DARK HORSE: DISCOVERY OF AN ULTRA-FAINT MILKY WAY SATELLITE IN PEGASUS". The Astrophysical Journal Letters. 804 (2): L44. arXiv:1503.08268Freely accessible. doi:10.1088/2041-8205/804/2/L44.
  15. ↑ Kim, Dongwon; Jerjen, Helmut; Geha, Marla; Chiti, Anirudh; Milone, Antonino P.; Mackey, Dougal; da Costa, Gary; Frebel, Anna; Conn, Blair. "PORTRAIT OF A DARK HORSE: PHOTOMETRIC PROPERTIES AND KINEMATICS OF THE ULTRA-FAINT MILKY WAY SATELLITE PEGASUS III". arXiv:1608.04934Freely accessible [astro-ph.GA].
  16. 1 2 3 4 5 6 7 8 A. Drlica-Wagner; et al. (4 November 2015). "Eight ultra-faint galaxy candidates discovered in Year Two of the Dark Energy Survey". The Astrophysical Journal. 813 (2): 109. arXiv:1508.03622Freely accessible. Bibcode:2015ApJ...813..109D. doi:10.1088/0004-637X/813/2/109.
  17. ↑ Dongwon Kim & Helmut Jerjen (28 July 2015). "Horologium II: A second ultra-faint Milky Way satellite in the Horologium constellation". The Astrophysical Journal Letters. 808 (2): L39. arXiv:1505.04948Freely accessible. Bibcode:2015ApJ...808L..39K. doi:10.1088/2041-8205/808/2/L39.
  18. 1 2 Laevens, B.P.M; Martin, N.F.; Bernard, E.J.; Schlafly, E.F.; Sesar, B. (1 November 2015). "SAGITTARIUS II, DRACO II AND LAEVENS 3: THREE NEW MILKY WAY SATELLITES DISCOVERED IN THE PAN-STARRS 1 3π SURVEY". The Astrophysical Journal. 813 (1). arXiv:1507.07564Freely accessible. doi:10.1088/0004-637X/813/1/44.
  19. ↑ E. Luque; et al. (9 February 2016). "Digging deeper into Southern skies: a compact Milky Way companion discovered in first-year Dark Energy Survey data". Monthly Notices of the Royal Astronomical Society. 458 (1): 603–612. arXiv:1508.02381Freely accessible. Bibcode:2016MNRAS.458..603L. doi:10.1093/mnras/stw302.
  20. ↑ G. Torrealba, S.E. Koposov, V. Belokurov & M. Irwin (13 April 2016). "The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater". Monthly Notices of the Royal Astronomical Society. Bibcode:2016MNRAS.tmp..635T. doi:10.1093/mnras/stw733.
  21. ↑ Torrealba, G.; Koposov, S.E.; Belokurov, V.; Irwin, M.; Collins, M.; Spencer, M.; Ibata, R.; Matteo, M.; Bonaca, A.; Jethwa, P. "At the survey limits: discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data". arXiv:1605.05338Freely accessible [astro-ph.GA].

Further reading


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