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, which is part of the local galaxy cluster, the Local Group. [1]

Contents

There are 61 small galaxies confirmed to be within 420 kiloparsecs (1.4 million light-years ) of the Milky Way, [2] 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. [3] Of the galaxies confirmed to be in orbit, the largest is the Sagittarius Dwarf Spheroidal Galaxy, which has a diameter of 2.6 kiloparsecs (8,500 ly) [4] or roughly a twentieth 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 980,000 ly (300 kpc) from the center of the galaxy, [a] 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. [5] [6]

List

The Milky Way's satellite galaxies include the following: [7] [2]

NameDiameter (kpc)Distance
(kpc)		 Absolute visual magnitude Type Discovered
Large Magellanic Cloud 448.5−18.1SBmprehistoric
Antlia 2 2.9130−8.5Irr?2018
Sagittarius Dwarf 2.620−13.5E1994
Crater II 2.2117.5−8.2dSph2016 [8]
Small Magellanic Cloud 261−16.8Irrprehistoric
Canes Venatici I 1.1220−8.6dSph2006
Canis Major Dwarf 1.58−14.4Irr2003
Boötes III 1.046−5.75dSph?2009
Sculptor Dwarf 0.890−11.1dE31937
Draco Dwarf 0.780−8.8dE01954
Hercules 0.7135−6.6dSph2006
Leo II 0.7210−9.8dE01950
Fornax Dwarf 0.6140−13.4dE21938
Eridanus II [9] 0.55366−7.1dSph2015 [10] [11]
Sextans Dwarf Spheroidal 0.590−9.3dE31990
Carina Dwarf Spheroidal 0.5100−9.1dE31977
Leo I 0.5250−12.0dE31950
Ursa Minor Dwarf 0.460−8.8dE41954
Leo T 0.34420−8.0dSph/dIrr2006
Aquarius II 0.32108−4.2dSph2016 [12]
Boötes I 0.3060−6.3dSph2006
Canes Venatici II 0.30155−4.9dSph2006
Leo IV 0.30160−5.8dSph2006
Tucana IV 0.2548−3.5dSph2015 [13]
Columba I 0.21182−4.5dSph2015 [13]
Ursa Major II Dwarf 0.2030−4.25dG D2006
Grus II 0.1953−3.9dSph2015 [13]
Cetus III 0.18251−2.4dSph?2017 [14]
Coma Berenices 0.1442−4.1dG D2006
Hydra II 0.14128−4.8dSph2015 [15]
Reticulum III 0.1392−3.3dSph2015 [13]
Pisces II 0.12180−5.0Sph2010
Pegasus III 0.11215−3.4dSph2015 [16] [17]
Hydrus I 0.1028−4.7dSph2018 [18]
Boötes II 0.1042−2.7dSph2007
Tucana III 0.0925−2.4dSph2015 [13]
Virgo I 0.0991−0.3dSph2016 [14]
Horologium II 0.0978−2.6dSph2015 [19]
Sagittarius II 0.0867−5.2dSph2015 [20]
Leo V 0.08180−5.2dSph2007
Triangulum II 0.0730−1.8dSph2015
Segue 2 0.0735−2.5dSph2007
Segue 1 0.0623−1.5dSph2007
Draco II 0.0420−2.9dSph2015 [20]
Tucana V 0.0355−1.6dSph2015 [13]
Cetus II 0.03300.0dSph?2015 [13]
Reticulum II 0.06430−3.6dSph2015 [10] [11]
Tucana II 0.3370−3.9dSph2015 [10] [11]
Pisces Overdensity 1.580−13dSph?2009
DES 1 0.0282−3.05dSph?2016 [21]
Eridanus III 0.02890−2.4dSph? [b] 2015 [10] [11]
Horologium I 0.06100−3.5dSph? [b] 2015 [10] [11]
Kim 2/Indus I 0.074100−3.5GC/dSph2015 [10] [11]
Phoenix II 0.0521100−3.7dSph? [b] 2015 [10] [11]
Ursa Major I Dwarf 0.64100−5.5dG Sph2005
Pictoris I 0.058115−3.7dSph? [b] 2015 [10] [11]
Grus I 0.12120−3.4dSph2015 [10]
Pegasus IV 0.08290−4.25dSph2022 [22]
Carina II 0.18236−4.5dSph2018 [23]
Carina III 0.0628−2.4GC?2018 [23]
Boötes IV 0.28209−4.53dSph2019 [24]
Centaurus I 0.076116−5.55dSph2020 [25]
Pictor II 0.04646−3.2dSph2016 [26]
Boötes V 0.0194102−3.2dSph?2022 [27]
Leo Minor I 0.089659441282−2.4dSph2022 [27]
Virgo II 0.0772−1.6dSph2022 [27]
Willman 1 0.0238−2.53dSph2018 [28]
Ursa Major III 0.00310+2.2dSph2023
Leo K 0.0087434−4.86dSph2024 [29]
Leo M 0.009459−5.77dSph2024 [29]
Sextans II 0.024?--dSph2024 [30]
Virgo III 0.015154 [31] -dSph2024 [30]
Pegasus W0.01227+1dSph2020
Segue 30.076145.6+0.7dSph2003
Eridanus IV0.03459.7+0.2dSph?2021
Laevens 1 (Crater 1)0.0926.8+0.8dG D2014
Leo VI0.28111−3.56dSph2024 [32]
Aquarius III0.10285−2.5dSph2024 [33]

Map with clickable regions

Milky Way's satellite galaxies (clickable map) Satellite Galaxies.svg
Milky Way's satellite galaxies (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

Notes

  1. ↑ The distance to edge of the dark matter halo of the galaxy from its center is the virial radius of a galaxy, Rvir
  2. 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. 92 (9) (published September 2013): 959–963. arXiv: 1310.0014 . Bibcode:2014CaJPh..92..959T. doi:10.1139/cjp-2013-0429. S2CID   118390693.
    2. 1 2 A. Drlica-Wagner (2020). "The Astrophysical Journal | Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1". The Astrophysical Journal. 893 (1): 47. doi: 10.3847/1538-4357/ab7eb9 . hdl: 10150/642363 . S2CID   208857848.
    3. ↑ "Press release: Magellanic Clouds May Be Just Passing Through". Harvard University. January 9, 2007.
    4. ↑ 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 .
    5. ↑ "Milky Way Ransacks Nearby Dwarf Galaxies". SpaceDaily. 17 October 2014.
    6. ↑ "Milky Way ransacks nearby dwarf galaxies". ScienceDaily. 15 October 2014.
    7. ↑ Sjölander, Nils. "Milky Way satellite galaxies". Archived from the original on 2014-02-19.
    8. ↑ Torrealba, G.; Koposov, S.E.; Belokurov, V.; Irwin, M. (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. 459 (3): 2370–2378. arXiv: 1601.07178 . Bibcode:2016MNRAS.459.2370T. doi: 10.1093/mnras/stw733 .
    9. ↑ Crnojević, D.; Sand, D.J.; Zaritsky, D.; Spekkens, K.; Willman, B.; Hargis, J.R. (2016). "Deep imaging of Eridanus II and its lone star cluster". The Astrophysical Journal. 824 (1): L-14. arXiv: 1604.08590 . Bibcode:2016ApJ...824L..14C. doi: 10.3847/2041-8205/824/1/L14 . S2CID   2202492.
    10. 1 2 3 4 5 6 7 8 9 Koposov, Sergey E.; Belokurov, Vasily; Torrealba, Gabriel; Evans, N. Wyn (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 (2): 130. arXiv: 1503.02079 . Bibcode:2015ApJ...805..130K. doi:10.1088/0004-637X/805/2/130. S2CID   118267222.
    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 (1): 50. arXiv: 1503.02584 . Bibcode:2015ApJ...807...50B. doi:10.1088/0004-637X/807/1/50. S2CID   12011753.
    12. ↑ Torrealba, G.; Koposov, S.E.; Belokurov, V.; Irwin, M.; Collins, M.; Spencer, M.; Ibata, R.; Matteo, M.; Bonaca, A.; Jethwa, P. (2016). "At the survey limits: Discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data". Monthly Notices of the Royal Astronomical Society. 463 (1): 712–722. arXiv: 1605.05338 . Bibcode:2016MNRAS.463..712T. doi: 10.1093/mnras/stw2051 .
    13. 1 2 3 4 5 6 7 Drlica-Wagner, A.; 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: 1508.03622 . Bibcode:2015ApJ...813..109D. doi:10.1088/0004-637X/813/2/109. S2CID   55909299.
    14. 1 2 Homma, Daisuke; Chiba, Masashi; Okamoto, Sakurako; Komiyama, Yutaka; Tanaka, Masayuki; Tanaka, Mikito; Ishigaki, Miho N.; Hayashi, Kohei; Arimoto, Nobuo (2017-04-19). "Searches for New Milky Way Satellites from the First Two Years of Data of the Subaru/Hyper Suprime-Cam Survey: Discovery of Cetus III". Publications of the Astronomical Society of Japan. 70: S18. arXiv: 1704.05977 . Bibcode:2018PASJ...70S..18H. doi:10.1093/pasj/psx050.
    15. ↑ 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: 1503.06216 . Bibcode:2015ApJ...804L...5M. doi:10.1088/2041-8205/804/1/L5. S2CID   7814048.
    16. ↑ 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): L-44. arXiv: 1503.08268 . Bibcode:2015ApJ...804L..44K. doi:10.1088/2041-8205/804/2/L44. S2CID   119302178.
    17. ↑ Kim, Dongwon; Jerjen, Helmut; Geha, Marla; Chiti, Anirudh; Milone, Antonino P.; Mackey, Dougal; da Costa, Gary; Frebel, Anna; Conn, Blair (2016). "Portrait of a dark horse: Photometric properties and kinematics of the ultra-faint Milky Way satellite Pegasus III". The Astrophysical Journal. 833 (1): 16. arXiv: 1608.04934 . Bibcode:2016ApJ...833...16K. doi: 10.3847/0004-637X/833/1/16 . S2CID   73677994.
    18. ↑ Koposov, Sergey E.; Walker, Matthew G.; Belokurov, Vasily; Casey, Andrew R.; Geringer-Sameth, Alex; Mackey, Dougal; Da Costa, Gary; Erkal, Denis; Jethwa, Prashin (2018-10-01). "Snake in the Clouds: a new nearby dwarf galaxy in the Magellanic bridge*". Monthly Notices of the Royal Astronomical Society. 479 (4): 5343–5361. arXiv: 1804.06430 . Bibcode:2018MNRAS.479.5343K. doi: 10.1093/mnras/sty1772 . ISSN   0035-8711.
    19. ↑ Kim, Dongwon & Jerjen, Helmut (28 July 2015). "Horologium II: A second ultra-faint Milky Way satellite in the Horologium constellation". The Astrophysical Journal Letters. 808 (2): L-39. arXiv: 1505.04948 . Bibcode:2015ApJ...808L..39K. doi:10.1088/2041-8205/808/2/L39. S2CID   117190468.
    20. 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): 44. arXiv: 1507.07564 . Bibcode:2015ApJ...813...44L. doi:10.1088/0004-637X/813/1/44. S2CID   54042426.
    21. ↑ Luque, E.; 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: 1508.02381 . Bibcode:2016MNRAS.458..603L. doi: 10.1093/mnras/stw302 .
    22. ↑ Cerny, W.; et al. (2023). "Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus". The Astrophysical Journal. 942 (2): 111. arXiv: 2203.11788 . Bibcode:2023ApJ...942..111C. doi: 10.3847/1538-4357/aca1c3 . S2CID   247597301.
    23. 1 2 Torrealba, G.; Belokurov, V.; Koposov, S. E.; Bechtol, K.; Drlica-Wagner, A.; Olsen, K. A. G.; Vivas, A. K.; Yanny, B.; Jethwa, P. (22 January 2018). "Discovery of two neighbouring satellites in the Carina constellation with MagLiteS". Monthly Notices of the Royal Astronomical Society. 475 (4): 5085–5097. arXiv: 1801.07279 . doi: 10.1093/mnras/sty170 .
    24. ↑ Homma (2019). "Boötes. IV. A new Milky Way satellite discovered in the Subaru Hyper Suprime-Cam Survey and implications for the missing satellite problem". Publications of the Astronomical Society of Japan. 71 (5): 94. arXiv: 1906.07332 . Bibcode:2019PASJ...71...94H. doi:10.1093/pasj/psz076.
    25. ↑ Mau (2020). "Two Ultra-faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Survey". The Astrophysical Journal. 890 (2): 136. arXiv: 1912.03301 . Bibcode:2020ApJ...890..136M. doi: 10.3847/1538-4357/ab6c67 . S2CID   208857609.
    26. ↑ Drlica-Wagner (2016). "An Ultra-Faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey". The Astrophysical Journal. 833 (1): L5. arXiv: 1609.02148 . Bibcode:2016ApJ...833L...5D. doi: 10.3847/2041-8205/833/1/L5 . hdl:1885/153579. S2CID   56071154.
    27. 1 2 3 Cerny, W.; et al. (2023). "Six More Ultra-faint Milky Way Companions Discovered in the DECam Local Volume Exploration Survey". The Astrophysical Journal. 953 (1): 1. arXiv: 2209.12422 . Bibcode:2023ApJ...953....1C. doi: 10.3847/1538-4357/acdd78 .
    28. ↑ Muñoz (2018). "A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters". The Astrophysical Journal. 860 (1): 66. arXiv: 1806.06891 . Bibcode:2018ApJ...860...66M. doi: 10.3847/1538-4357/aac16b . S2CID   118978019.
    29. 1 2 McQuinn, Kristen. B. W.; Mao, Yao-Yuan; Tollerud, Erik J.; Cohen, Roger E.; Shih, David; Buckley, Matthew R.; Dolphin, Andrew E. (2024). "Discovery and Characterization of Two Ultrafaint Dwarfs outside the Halo of the Milky Way: Leo M and Leo K". The Astrophysical Journal. 967 (2): 161. arXiv: 2307.08738 . Bibcode:2024ApJ...967..161M. doi: 10.3847/1538-4357/ad429b .
    30. 1 2 Robert Lea (2024-07-02). "Scientists finally found 2 of the Milky Way's missing satellite galaxies. What could this mean for astronomy?". Space.com. Retrieved 2024-07-04.
    31. ↑ Ngeow, Chow-Choong; Bhardwaj, Anupam (2024). "Discovery of RR Lyrae in the Ultra-faint-dwarf Galaxy Virgo III". The Astronomical Journal. 168 (1): 8. arXiv: 2405.05482 . Bibcode:2024AJ....168....8N. doi: 10.3847/1538-3881/ad49a9 .
    32. ↑ Tan, C. Y.; et al. (2025). "A Pride of Satellites in the Constellation Leo? Discovery of the Leo VI Milky Way Satellite Ultra-faint Dwarf Galaxy with DELVE Early Data Release 3". The Astrophysical Journal. 979 (2): 176. arXiv: 2408.00865 . Bibcode:2025ApJ...979..176T. doi: 10.3847/1538-4357/ad9b0c .
    33. ↑ Cerny, W.; et al. (2025). "Discovery and Spectroscopic Confirmation of Aquarius III: A Low-mass Milky Way Satellite Galaxy". The Astrophysical Journal. 979 (2): 164. arXiv: 2410.00981 . Bibcode:2025ApJ...979..164C. doi: 10.3847/1538-4357/ad8eba .

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