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Satellite galaxies of the Milky Way

Galaxies bound to the Milky Way

Galaxies bound to 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.

There are 61 small galaxies confirmed to be within 420 kpc 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. Of the galaxies confirmed to be in orbit, the largest is the Sagittarius Dwarf Spheroidal Galaxy, which has a diameter of 2.6 kpc{{cite journal

Characteristics

Satellite galaxies that orbit from 1000 ly of the edge of the disc of the Milky Way Galaxy to the edge of the dark matter halo 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:

NameDiameter (kpc)Distance
(kpc)Absolute visual magnitudeTypeDiscovered
Large Magellanic Cloud448.5−18.1SBmprehistoric
Antlia 22.9130−8.5Irr?2018
Sagittarius Dwarf2.620−13.5E1994
Crater II2.2117.5−8.2dSphtitle=The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Craterauthor1=Torrealba, G.author2=Koposov, S.E.author3=Belokurov, V.author4=Irwin, M.journal=Monthly Notices of the Royal Astronomical Societydoi=10.1093/mnras/stw733date=13 April 2016bibcode=2016MNRAS.459.2370Tvolume=459issue=3pages=2370–2378doi-access=freearxiv=1601.07178}}
Small Magellanic Cloud261−16.8Irrprehistoric
Canes Venatici I1.1220−8.6dSph2006
Canis Major Dwarf1.58−14.4Irr2003
Boötes III1.046−5.75dSph?2009
Sculptor Dwarf0.890−11.1dE31937
Draco Dwarf0.780−8.8dE01954
Hercules0.7135−6.6dSph2006
Leo II0.7210−9.8dE01950
Fornax Dwarf0.6140−13.4dE21938
title=Deep imaging of Eridanus II and its lone star clusterjournal=The Astrophysical Journalvolume=824issue=1page=L-14first1=D.last1=Crnojevićfirst2=D.J.last2=Sandfirst3=D.last3=Zaritskyauthor4-link=Kristine Spekkensfirst4=K.last4=Spekkensfirst5=B.last5=Willmanfirst6=J.R.last6=Hargisarxiv=1604.08590bibcode=2016ApJ...824L..14Cdoi=10.3847/2041-8205/824/1/L14year=2016s2cid=2202492doi-access=free }}0.55366−7.1dSph2015
Sextans Dwarf Spheroidal0.590−9.3dE31990
Carina Dwarf Spheroidal0.5100−9.1dE31977
Leo I0.5250−12.0dE31950
Ursa Minor Dwarf0.460−8.8dE41954
Leo T0.34420−8.0dSph/dIrr2006
Aquarius II0.32108−4.2dSphtitle=At the survey limits: Discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS datafirst1=G.last1=Torrealbafirst2=S.E.last2=Koposovfirst3=V.last3=Belokurovfirst4=M.last4=Irwinfirst5=M.last5=Collinsfirst6=M.last6=Spencerfirst7=R.last7=Ibatafirst8=M.last8=Matteofirst9=A.last9=Bonacafirst10=P.last10=Jethwaarxiv=1605.05338doi=10.1093/mnras/stw2051volume=463issue=1journal=Monthly Notices of the Royal Astronomical Societypages=712–722bibcode=2016MNRAS.463..712Tyear=2016doi-access=free }}
Boötes I0.3060−6.3dSph2006
Canes Venatici II0.30155−4.9dSph2006
Leo IV0.30160−5.8dSph2006
Tucana IV0.2548−3.5dSph2015
Columba I0.21182−4.5dSph2015
Ursa Major II Dwarf0.2030−4.25dG D2006
Grus II0.1953−3.9dSphtitle=Eight ultra-faint galaxy candidates discovered in Year Two of the Dark Energy Surveyauthor1=Drlica-Wagner, A.display-authors=etaljournal=The Astrophysical Journalvolume=813issue=2page=109doi=10.1088/0004-637X/813/2/109date=4 November 2015arxiv = 1508.03622bibcode=2015ApJ...813..109Ds2cid=55909299 }}
Cetus III0.18251−2.4dSph?last1=Hommafirst1=Daisukelast2=Chibafirst2=Masashilast3=Okamotofirst3=Sakurakolast4=Komiyamafirst4=Yutakalast5=Tanakafirst5=Masayukilast6=Tanakafirst6=Mikitolast7=Ishigakifirst7=Miho N.last8=Hayashifirst8=Koheilast9=Arimotofirst9=Nobuodate=2017-04-19title=Searches for New Milky Way Satellites from the First Two Years of Data of the Subaru/Hyper Suprime-Cam Survey: Discovery of Cetus IIIjournal=Publications of the Astronomical Society of Japanvolume=70pages=S18arxiv=1704.05977doi=10.1093/pasj/psx050bibcode=2018PASJ...70S..18H }}
Coma Berenices0.1442−4.1dG D2006
Hydra II0.14128−4.8dSphtitle=Hydra II: A faint and compact Milky Way dwarf galaxy found in the survey of the Magellanic stellar historyfirst=Nicolas F.last=Martincollaboration=Survey of the Magellanic Stellar Historyjournal=The Astrophysical Journal Lettersdate=23 April 2015volume=804issue=1pages=L5doi=10.1088/2041-8205/804/1/L5arxiv = 1503.06216bibcode = 2015ApJ...804L...5Ms2cid=7814048 }}
Reticulum III0.1392−3.3dSph2015
Pisces II0.12180−5.0Sph2010
Pegasus III0.11215−3.4dSphtitle=A hero's dark horse: Discovery of an ultra-faint Milky Way satellite in Pegasusfirst1=Dongwonlast1=Kimfirst2=Helmutlast2=Jerjenfirst3=Dougallast3=Mackeyfirst4=Gary S.last4=Da Costafirst5=Antonino P.last5=Milonejournal=The Astrophysical Journal Lettersdate=12 May 2015volume=804issue=2page=L-44doi=10.1088/2041-8205/804/2/L44arxiv=1503.08268bibcode=2015ApJ...804L..44Ks2cid=119302178 }}
Hydrus I0.1028−4.7dSphlast1=Koposovfirst1=Sergey E.last2=Walkerfirst2=Matthew G.last3=Belokurovfirst3=Vasilylast4=Caseyfirst4=Andrew R.last5=Geringer-Samethfirst5=Alexlast6=Mackeyfirst6=Dougallast7=Da Costafirst7=Garylast8=Erkalfirst8=Denislast9=Jethwafirst9=Prashindate=2018-10-01title=Snake in the Clouds: a new nearby dwarf galaxy in the Magellanic bridge*journal=Monthly Notices of the Royal Astronomical Societylanguage=envolume=479issue=4pages=5343–5361doi=10.1093/mnras/sty1772doi-access=freeissn=0035-8711arxiv=1804.06430bibcode=2018MNRAS.479.5343K }}
Boötes II0.1042−2.7dSph2007
Tucana III0.0925−2.4dSph2015
Virgo I0.0991−0.3dSph2016
Horologium II0.0978−2.6dSphtitle=Horologium II: A second ultra-faint Milky Way satellite in the Horologium constellationdate=28 July 2015author1=Kim, Dongwonauthor2=Jerjen, Helmutname-list-style=ampjournal=The Astrophysical Journal Lettersvolume=808issue=2page=L–39doi=10.1088/2041-8205/808/2/L39arxiv=1505.04948bibcode=2015ApJ...808L..39Ks2cid=117190468 }}
Sagittarius II0.0867−5.2dSph2015
Leo V0.08180−5.2dSph2007
Triangulum II0.0730−1.8dSph2015
Segue 20.0735−2.5dSph2007
Segue 10.0623−1.5dSph2007
Draco II0.0420−2.9dSphtitle=Sagittarius II, Draco II and Laevens 3: Three new Milky Way satellites discovered in the PAN-STARRS 1 3π surveylast1=Laevensfirst1=B.P.Mlast2=Martinfirst2=N.F.last3=Bernardfirst3=E.J.last4=Schlaflyfirst4=E.F.last5=Sesarfirst5=B.journal=The Astrophysical Journaldate=1 November 2015volume=813issue=1page=44doi=10.1088/0004-637X/813/1/44arxiv=1507.07564bibcode=2015ApJ...813...44Ls2cid=54042426 }}
Tucana V0.0355−1.6dSph2015
Cetus II0.03300.0dSph?2015
Reticulum II0.06430−3.6dSphtitle=Beasts of the Southern Wild. Discovery of a large number of ultra faint satellites in the vicinity of the Magellanic Cloudsauthor1=Koposov, Sergey E.author2=Belokurov, Vasilyauthor3=Torrealba, Gabrielauthor4=Evans, N. Wyndate=10 March 2015arxiv=1503.02079journal=The Astrophysical Journalbibcode=2015ApJ...805..130Kdoi=10.1088/0004-637X/805/2/130volume=805issue=2pages=130s2cid=118267222 }}
Tucana II0.3370−3.9dSph2015
Pisces Overdensity1.580−13dSph?2009
DES 10.0282−3.05dSph?title=Digging deeper into Southern skies: A compact Milky Way companion discovered in first-year Dark Energy Survey dataauthor1=Luque, E.display-authors=etaljournal=Monthly Notices of the Royal Astronomical Societyvolume=458issue=1pages=603–612doi=10.1093/mnras/stw302date=9 February 2016doi-access=freearxiv=1508.02381bibcode=2016MNRAS.458..603L}}
Eridanus III0.02890−2.4dSph?2015
Horologium I0.06100−3.5dSph?2015
Kim 2/Indus I0.074100−3.5GC/dSph2015
Phoenix II0.0521100−3.7dSph?2015
Ursa Major I Dwarf0.64100−5.5dG Sph2005
Pictoris I0.058115−3.7dSph?2015
Grus I0.12120−3.4dSph2015
Pegasus IV0.08290−4.25dSpharxiv=2203.11788doi=10.3847/1538-4357/aca1c3title=Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasusyear=2023last1=Cernyfirst1=W.last2=Simonfirst2=J. D.last3=Lifirst3=T. S.last4=Drlica-Wagnerfirst4=A.last5=Pacefirst5=A. B.last6=Martínez-Vázquezfirst6=C. E.last7=Rileyfirst7=A. H.last8=Mutlu-Pakdilfirst8=B.last9=Maufirst9=S.last10=Fergusonfirst10=P. S.last11=Erkalfirst11=D.last12=Munozfirst12=R. R.last13=Bomfirst13=C. R.last14=Carlinfirst14=J. L.last15=Carollofirst15=D.last16=Choifirst16=Y.last17=Jifirst17=A. P.last18=Manwadkarfirst18=V.last19=Martínez-Delgadofirst19=D.last20=Millerfirst20=A. E.last21=Noëlfirst21=N. E. D.last22=Sakowskafirst22=J. D.last23=Sandfirst23=D. J.last24=Stringfellowfirst24=G. S.last25=Tollerudfirst25=E. J.last26=Vivasfirst26=A. K.last27=Carballo-Bellofirst27=J. A.last28=Hernandez-Langfirst28=D.last29=Jamesfirst29=D. J.last30=Nideverfirst30=D. L.journal=The Astrophysical Journalvolume=942issue=2page=111bibcode=2023ApJ...942..111Cs2cid=247597301display-authors=1doi-access=free }}
Carina II0.18236−4.5dSphlast1=Torrealbafirst1=G.last2=Belokurovfirst2=V.last3=Koposovfirst3=S. E.last4=Bechtolfirst4=K.last5=Drlica-Wagnerfirst5=A.last6=Olsenfirst6=K. A. G.last7=Vivasfirst7=A. K.last8=Yannyfirst8=B.last9=Jethwafirst9=P.date=2018-01-22title=Discovery of two neighbouring satellites in the Carina constellation with MagLiteSjournal=Monthly Notices of the Royal Astronomical Societyvolume=475issue=4pages=5085–5097doi=10.1093/mnras/sty170doi-access=freearxiv=1801.07279df=dmy-all}}
Carina III0.0628−2.4GC?2018
Boötes IV0.28209−4.53dSphtitle=Boötes. IV. A new Milky Way satellite discovered in the Subaru Hyper Suprime-Cam Survey and implications for the missing satellite problemlast=Hommayear=2019journal=Publications of the Astronomical Society of Japanvolume=71issue=5page=94doi=10.1093/pasj/psz076url=https://academic.oup.com/pasj/article-abstract/71/5/94/5539816arxiv=1906.07332bibcode=2019PASJ...71...94H }}
Centaurus I0.076116−5.55dSphtitle=Two Ultra-faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Surveylast=Mauyear=2020journal=The Astrophysical Journalvolume=890issue=2page=136doi=10.3847/1538-4357/ab6c67arxiv=1912.03301bibcode=2020ApJ...890..136Ms2cid=208857609doi-access=free }}
Pictor II0.04646−3.2dSphauthor=Drlica-Wagnertitle=An Ultra-Faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Surveyyear=2016journal=The Astrophysical Journalvolume=833issue=1pages=L5doi=10.3847/2041-8205/833/1/L5arxiv=1609.02148bibcode=2016ApJ...833L...5Dhdl=1885/153579s2cid=56071154doi-access=free }}
Boötes V0.0194102−3.2dSph?doi=10.3847/1538-4357/acdd78doi-access=freetitle=Six More Ultra-faint Milky Way Companions Discovered in the DECam Local Volume Exploration Surveydate=2023last1=Cernyfirst1=W.last2=Martínez-Vázquezfirst2=C. E.last3=Drlica-Wagnerfirst3=A.last4=Pacefirst4=A. B.last5=Mutlu-Pakdilfirst5=B.last6=Lifirst6=T. S.last7=Rileyfirst7=A. H.last8=Crnojevićfirst8=D.last9=Bomfirst9=C. R.last10=Carballo-Bellofirst10=J. A.last11=Carlinfirst11=J. L.last12=Chitifirst12=A.last13=Choifirst13=Y.last14=Collinsfirst14=M. L. M.last15=Darragh-Fordfirst15=E.last16=Fergusonfirst16=P. S.last17=Gehafirst17=M.last18=Martínez-Delgadofirst18=D.last19=Massanafirst19=P.last20=Maufirst20=S.last21=Medinafirst21=G. E.last22=Muñozfirst22=R. R.last23=Nadlerfirst23=E. O.last24=Noëlfirst24=N. E. D.last25=Olsenfirst25=K. A. G.last26=Pieresfirst26=A.last27=Sakowskafirst27=J. D.last28=Simonfirst28=J. D.last29=Stringfellowfirst29=G. S.last30=Tollerudfirst30=E. J.journal=The Astrophysical Journalvolume=953issue=1page=1arxiv=2209.12422bibcode=2023ApJ...953....1Cdisplay-authors=1 }}
Leo Minor I0.089782−2.4dSph2022
Virgo II0.0772−1.6dSph2022
Willman 10.0238−2.53dSphtitle=A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameterslast=Muñozyear=2018journal=The Astrophysical Journalvolume=860issue=1page=66doi=10.3847/1538-4357/aac16barxiv=1806.06891bibcode=2018ApJ...860...66Ms2cid=118978019doi-access=free }}
Ursa Major III0.00310+2.2dSph2023
Leo K0.0087434−4.86dSphdoi=10.3847/1538-4357/ad429bdoi-access=freetitle=Discovery and Characterization of Two Ultrafaint Dwarfs outside the Halo of the Milky Way: Leo M and Leo Kdate=2024last1=McQuinnfirst1=Kristen. B. W.last2=Maofirst2=Yao-Yuanlast3=Tollerudfirst3=Erik J.last4=Cohenfirst4=Roger E.last5=Shihfirst5=Davidlast6=Buckleyfirst6=Matthew R.last7=Dolphinfirst7=Andrew E.journal=The Astrophysical Journalvolume=967issue=2page=161arxiv=2307.08738bibcode=2024ApJ...967..161M }}
Leo M0.009459−5.77dSph2024
Sextans II0.024?––dSphauthor1=Robert Leadate=2024-07-02title=Scientists finally found 2 of the Milky Way's missing satellite galaxies. What could this mean for astronomy?url=https://www.space.com/milky-way-satellite-dwarf-galaxies-foundaccess-date=2024-07-04website=Space.comlanguage=en}}
Virgo III0.015154–dSph2024
Pegasus W0.01227+1dSph2020
Eridanus IV0.03459.7+0.2dSph?2021
Laevens 1 (Crater 1)0.0926.8+0.8dG D2014
Leo VI0.28111−3.56dSph2024
Aquarius III0.10285−2.5dSph2024

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 rect 168 273 249 318 Large Magellanic Cloud rect 229 326 288 368 Small Magellanic Cloud rect 297 376 352 407 Sculptor Dwarf rect 183 446 234 476 Fornax Dwarf rect 107 297 150 332 Carina Dwarf rect 296 107 339 144 Bootes Dwarf rect 336 180 408 196 Ursa Major II rect 357 40 423 59 Ursa Major I rect 370 110 428 142 Ursa Minor Dwarf rect 430 119 470 154 Draco Dwarf

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.

Notes

References

References

  1. David G. Turner. (15 August 2013). "An Eclectic View of our Milky Way Galaxy". Canadian Journal of Physics.
  2. (January 9, 2007). "Press release: Magellanic Clouds May Be Just Passing Through". Harvard University.
  3. (17 October 2014). "Milky Way Ransacks Nearby Dwarf Galaxies". SpaceDaily.
  4. (15 October 2014). "Milky Way ransacks nearby dwarf galaxies". ScienceDaily.
  5. Sjölander, Nils. "Milky Way satellite galaxies".
  6. 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.
  7. (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.
  8. (2016). "Deep imaging of Eridanus II and its lone star cluster". The Astrophysical Journal.
  9. (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.
  10. (4 November 2015). "Eight ultra-faint galaxy candidates discovered in Year Two of the Dark Energy Survey". The Astrophysical Journal.
  11. (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.
  12. Martin, Nicolas F.. (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.
  13. (12 May 2015). "A hero's dark horse: Discovery of an ultra-faint Milky Way satellite in Pegasus". The Astrophysical Journal Letters.
  14. (2016). "Portrait of a dark horse: Photometric properties and kinematics of the ultra-faint Milky Way satellite Pegasus III". The Astrophysical Journal.
  15. (2018-10-01). "Snake in the Clouds: a new nearby dwarf galaxy in the Magellanic bridge*". Monthly Notices of the Royal Astronomical Society.
  16. (28 July 2015). "Horologium II: A second ultra-faint Milky Way satellite in the Horologium constellation". The Astrophysical Journal Letters.
  17. (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.
  18. (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.
  19. DES Collaboration. (10 March 2015). "Eight New Milky Way companions discovered in first-year Dark Energy Survey data". The Astrophysical Journal.
  20. (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.
  21. (2023). "Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus". The Astrophysical Journal.
  22. (2018-01-22). "Discovery of two neighbouring satellites in the Carina constellation with MagLiteS". Monthly Notices of the Royal Astronomical Society.
  23. 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.
  24. Mau. (2020). "Two Ultra-faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Survey". The Astrophysical Journal.
  25. Drlica-Wagner. (2016). "An Ultra-Faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey". The Astrophysical Journal.
  26. (2023). "Six More Ultra-faint Milky Way Companions Discovered in the DECam Local Volume Exploration Survey". The Astrophysical Journal.
  27. Muñoz. (2018). "A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters". The Astrophysical Journal.
  28. (2024). "Discovery and Characterization of Two Ultrafaint Dwarfs outside the Halo of the Milky Way: Leo M and Leo K". The Astrophysical Journal.
  29. (2024-07-02). "Scientists finally found 2 of the Milky Way's missing satellite galaxies. What could this mean for astronomy?".
  30. (2024). "Discovery of RR Lyrae in the Ultra-faint-dwarf Galaxy Virgo III". The Astronomical Journal.
  31. (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.
  32. (2025). "Discovery and Spectroscopic Confirmation of Aquarius III: A Low-mass Milky Way Satellite Galaxy". The Astrophysical Journal.
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