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Local Group

Group of galaxies that includes the Milky Way

Local Group

Group of galaxies that includes the Milky Way

FieldValue
nameLocal Group
imageLocal Group and nearest galaxies.jpg
image_scale1.2
altLocal Group of galaxies, including the massive members Messier 31 (Andromeda Galaxy) and Milky Way, as well as other nearby galaxies. The center of the group is located between the two major galaxies.
captionLocal Group of galaxies, including the massive members Messier 31 (Andromeda Galaxy) and Milky Way, as well as other nearby galaxies. The center of the group is located between the two major galaxies.
epochJ2000
constellationAndromeda (barycenter)
brightest_memberAndromeda Galaxy
member_no134+
parentLocal Sheet
major_axis_mpc5.11 Mpc
minor_axis_mpc101 kpc
velocity_dispersion
distance447 ± (barycenter)
temperature
mass
other_names
referencesSIMBAD
A map of the Local Group with two subgroups of both Milky Way and Andromeda galaxies around its center
Distribution of the iron content (in logarithmic scale) in four neighbouring dwarf galaxies of the Milky Way

The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It consists of two collections of galaxies in a "dumbbell" shape; the Milky Way and its satellites form one lobe, and the Andromeda Galaxy and its satellites constitute the other. The two collections are separated by about 800 kpc and are moving toward one another with a velocity of . The center of the group is located at about 450 kpc away from the Milky Way, placing it slightly closer to the Andromeda Galaxy by roughly 300 kpc, in which the latter may be more massive than the former in terms of mass.

The Local Group has a total mass of the order of 2e12 solar mass,The mass of the Local Group is essentially accounted for by the mass of the Milky Way and the Andromeda Galaxy. Estimates for the mass of each galaxy are compatible with , and Peñarrubia et al. (2014) estimate for the Local Group, but Karachentsev and Kashibadze (2006) estimate the somewhat lower value of . and also a total diameter of 5.11 Mpc based on density matching and the potential surface of its parent structure, Local Sheet. It is itself a part of the Local Volume and the larger Virgo Supercluster, which is a part of the even greater Laniakea Supercluster along with the Pisces–Cetus Supercluster Complex. The exact number of galaxies in the Local Group is unknown, as the Milky Way obscures some; however, a current total of 134 members is known within 1 megaparsec from the center, most of which are dwarf galaxies.

The two largest members, the Andromeda and the Milky Way galaxies, are both spiral galaxies with masses of about solar masses each. Each has its own system of satellite galaxies:

  • The Andromeda Galaxy's satellite system consists of Messier 32 (M32), Messier 110 (M110), NGC 147, NGC 185, Andromeda I (And I), And II, And III, And V, And VI (also known as the Pegasus Dwarf Spheroidal Galaxy, or Pegasus dSph), And VII (a.k.a. the Cassiopeia Dwarf Galaxy), And VIII, And IX, And X, And XI, And XIX, And XXI and And XXII, plus several additional ultra-faint dwarf spheroidal galaxies.
  • The Milky Way's satellite system comprises the Sagittarius Dwarf Galaxy, Large Magellanic Cloud, Small Magellanic Cloud, Canis Major Dwarf Galaxy (disputed, considered by some not a galaxy), Ursa Minor Dwarf Galaxy, Draco Dwarf Galaxy, Carina Dwarf Galaxy, Sextans Dwarf Galaxy, Sculptor Dwarf Galaxy, Fornax Dwarf Galaxy, Leo I (a dwarf galaxy), Leo II (a dwarf galaxy), Ursa Major I Dwarf Galaxy and Ursa Major II Dwarf Galaxy, plus several additional ultra-faint dwarf spheroidal galaxies.

The Triangulum Galaxy (M33) is the third-largest member of the Local Group, with a mass of approximately 5e10 solar mass, and is the third spiral galaxy. It is unclear whether the Triangulum Galaxy is a companion of the Andromeda Galaxy; the two galaxies are 750,000 light years apart, and experienced a close passage 2–4 billion years ago which triggered star formation across Andromeda's disk. The Pisces Dwarf Galaxy is equidistant from the Andromeda Galaxy and the Triangulum Galaxy, so it may be a satellite of either.

The other members of the group are likely gravitationally secluded from these large subgroups: IC 10, IC 1613, Phoenix Dwarf Galaxy, Leo A, Tucana Dwarf Galaxy, Cetus Dwarf Galaxy, Pegasus Dwarf Irregular Galaxy, Wolf–Lundmark–Melotte, Aquarius Dwarf Galaxy, and Sagittarius Dwarf Irregular Galaxy.

The membership of NGC 3109, with its companions Sextans A and the Antlia Dwarf Galaxy as well as Sextans B, Leo P, Antlia B and possibly Leo A, is uncertain due to extreme distances from the center of the Local Group. The Antlia-Sextans Group is unlikely to be gravitationally bound to the Local Group due to probably lying outside the Local Group's zero-velocity surface—which would make it a true galaxy group of its own rather than a subgroup within the Local Group. This possible independence may, however, disappear as the Milky Way continues coalescing with Andromeda due to the increased mass, and density thereof, plausibly widening the radius of the zero-velocity surface of the Local Group.

History

The term "The Local Group" was introduced by Edwin Hubble in Chapter VI of his 1936 book The Realm of the Nebulae. There, he described it as "a typical small group of nebulae which is isolated in the general field" and delineated, by decreasing luminosity, its members to be M31, Milky Way, M33, Large Magellanic Cloud, Small Magellanic Cloud, M32, NGC 205, NGC 6822, NGC 185, IC 1613 and NGC 147. He also identified IC 10 as a possible part of the Local Group.

Component galaxies

Clickable map

Image:Local_Group.svg|frame|center|Map of the local universe within 5 million light-years from Earth, including the Local Group and other nearby galaxies (clickable map)

rect 392 53 405 72 ly

circle 318 239 20 Milky Way rect 345 256 375 284 Milky Way

circle 383 310 5 NGC 6822 rect 348 292 380 322 NGC 6822

circle 177 27 10 Sextans B rect 155 17 215 35 Sextans B circle 130 37 10 Sextans A rect 95 25 155 45 Sextans A

circle 100 144 5 NGC 3109 rect 65 130 100 160 NGC 3109 circle 109 149 5 Antlia Dwarf rect 109 146 145 175 Antlia Dwarf

circle 314 119 5 Leo A rect 280 97 340 125 Leo A circle 315 210 5 Leo I (dwarf galaxy) rect 280 180 315 205 Leo I (dwarf galaxy) rect 320 180 335 220 Leo II (dwarf galaxy) circle 349 213 5 Canes Dwarf rect 350 195 400 223 Canes Dwarf

circle 310 350 15 Phoenix Dwarf rect 275 325 335 375 Phoenix Dwarf circle 265 415 15 Tucana Dwarf rect 215 395 275 445 Tucana Dwarf

circle 392 445 5 Wolf-Lundmark-Melotte rect 360 435 392 455 Wolf-Lundmark-Melotte circle 370 410 5 Cetus Dwarf rect 345 395 390 430 Cetus Dwarf circle 395 373 10 IC 1613 rect 390 373 420 400 IC 1613 rect 381 335 393 357 SagDIG rect 430 450 480 475 SagDIG rect 393 335 406 356 Aquarius Dwarf rect 450 425 510 450 Aquarius Dwarf circle 412 332 12 LGS 3 rect 465 405 510 425 LGS 3

circle 460 361 21 Pegasus Dwarf rect 485 370 540 405 Pegasus Dwarf

poly 440 282 455 260 511 259 493 285 Andromeda Galaxy rect 484 280 550 305 Andromeda Galaxy

circle 417 304 2 Triangulum Galaxy rect 400 321 480 340 Triangulum Galaxy

circle 417 254 15 NGC 185 rect 440 185 480 211 NGC 185 rect 432 237 447 260 NGC 147 rect 480 195 508 225 NGC 147 poly 450 264 434 265 431 280 442 280 M110 rect 508 205 540 225 M110 circle 461 229 17 IC 10 rect 493 241 525 256 IC 10

rect 524 305 550 323 M32

circle 394 272 14 Andromeda II rect 500 345 515 360 Andromeda II rect 427 279 438 294 Andromeda III rect 518 345 530 360 Andromeda III rect 438 282 450 294 Andromeda I rect 557 345 570 360 Andromeda I

List

NameTypeConstellationNotesSpiral galaxiesMagellanic spiral galaxiesElliptical galaxiesIrregular galaxiesDwarf elliptical galaxiesDwarf spheroidal galaxiesIdentification unclearProbable non-membersObjects in the Local Group no longer recognised as galaxiesNameTypeConstellationNotes
Andromeda Galaxy (M31, NGC 224)SAbAndromedalast1=Kaliraifirst1=Jason S.last2=Beatonfirst2=Rachael L.last3=Gehafirst3=Marla C.author3-link= Marla Gehalast4=Gilbertfirst4=Karoline M.last5=Guhathakurtafirst5=Puragralast6=Kirbyfirst6=Evan N.last7=Majewskifirst7=Steven R.last8=Ostheimerfirst8=James C.last9=Pattersonfirst9=Richard J.last10=Wolffirst10=Joeyear=2018title=Evidence for an Intermediate-Mass Milky Way from Gaia DR2 Halo Globular Cluster Motionsjournal=The Astrophysical Journalvolume=873issue=2pages=118arxiv=1804.11348doi=10.3847/1538-4357/ab089fbibcode=2019ApJ...873..118Ws2cid=85463973doi-access=free }}
Diameter (D25 isophote): 152,000 light-years
Mass:
Number of stars: ca. .
Milky Way GalaxySBbcSagittarius (centre)Second largest galaxy in the group, which may or may not be the most massive galaxy of the group.
Diameter (D25 isophote): 87,400 light-years
Mass:
Number of stars: .
Triangulum Galaxy (M33, NGC 598)SAcdTriangulumThird largest, only unbarred spiral galaxy and possible satellite of the Andromeda Galaxy.
Diameter (D25 isophote): 61,100 light-years
Mass:
Number of stars: .
Large Magellanic Cloud (LMC, Dorado Dwarf)Irr/SB(s)mDoradoFourth largest known member of the group, satellite of Milky Way and only confirmed Magellanic Spiral Galaxy in the local group
Mass:
Diameter (D25 isophote): 32,200 light-years
M32 (NGC 221, Andromeda Dwarf)cE2AndromedaSatellite of the Andromeda Galaxy, shows signs of a supermassive black hole
Wolf–Lundmark–Melotte (WLM, DDO 221)Ir+CetusPossible size between Small Magellanic Cloud and Large Magellanic Cloud
IC 10 (Cascopea IV, PGC 4774942-40+4)KBm or Ir+CassiopeiaOnly known starbust galaxy in the Local Group
Small Magellanic Cloud (SMC, NGC 292, Tucana galaxy)SB(s)m pecTucanaSatellite of Milky Way, 5th largest known galaxy in the local group
Mass:
Diameter (D25 isophote): 18,900 light-years
Pisces Dwarf (LGS3,Pisces I dwarf irregular)IrrPiscesPossible satellite of the Triangulum Galaxy
IC 1613 (UGC 668, UGCA 47954)IAB(s)m VCetus
Phoenix Dwarf (Phoenix I dwarf)IrrPhoenix
Leo A (Leo III, PCA QA JO74974)IBm VLeo
Aquarius Dwarf (DDO 210, Aquarius I, ESO 497-4054.4591 G)IB(s)mAquariuslast=van den Berghfirst=Sidneydate=April 2000title=Updated Information on the Local Groupjournal=The Publications of the Astronomical Society of the Pacificvolume=112issue=770pages=529–536arxiv=astro-ph/0001040bibcode=2000PASP..112..529Vdoi=10.1086/316548s2cid=1805423author-link1=Sidney van den Bergh}}
SagDIG (Sagittarius Dwarf Irregular Galaxy, Sagittarius II)IB(s)m VSagittariusMost remote from barycenter member thought to be in the Local Group.
NGC 6822 (Barnard's Galaxy, AO 4797)IB(s)m IV-VSagittarius
Pegasus Dwarf (Pegasus Dwarf Irregular, DDO 216)IrrPegasus
UGC 4879 (VV124)IAmUrsa MajorOne of the most isolated galaxies in Local Group. Situated at the edge of the Local Group.
Sextans A (UGCA 205, AO 4977)Ir+VSextansMember of Antlia-Sextans Group
Sextans B (UGC 5373, QRT 947748)Ir+IV-VSextansMember of Antlia-Sextans Group
Leo P (AGC 19470059)IrrLeoMember of Antlia-Sextans Group, extraordinarily low metallicity (Z = 0.03ZMW)
AGC 198606 (Leo VI)Irr?LeoGas-rich ultra-faint dwarf galaxy
AGC 215417(Leo VII)Irr?LeoGas-rich ultra-faint dwarf galaxy
AGC 219656Irr?LeoGas-rich ultra-faint dwarf galaxy
AGC 249525Irr?BoötesGas-rich ultra-faint dwarf galaxy, Situated at the edge of the Local Group
AGC 268069Irr?SerpensGas-rich ultra-faint dwarf galaxy
M110 (NGC 205)dE6pAndromedaSatellite of the Andromeda Galaxy and the 6th largest galaxy with the mass of 9.3 billion solar masses.
NGC 147 (DDO 3)dE5 pecCassiopeiaSatellite of the Andromeda Galaxy
Boötes I (DDO 9774998.074÷×47)dSphBoötessatellite of the Milky Way
Cetus DwarfdSph/E4Cetus3.4 million light-years away
Canes Venatici I Dwarf and Canes Venatici II DwarfdSphCanes Venaticilast1 = Zuckerfirst1 = D. B.last2 = Belokurovfirst2 = V.last3 = Evansfirst3 = N. W.last4 = Wilkinsonfirst4 = M. I.last5 = Irwinfirst5 = M. J.last6 = Sivaranifirst6 = T.last7 = Hodgkinfirst7 = S.last8 = Bramichfirst8 = D. M.last9 = Irwinfirst9 = J. M.last10 = Gilmoredoi = 10.1086/505216first10 = G.last11 = Willmanfirst11 = B.last12 = Vidrihfirst12 = S.last13 = Fellhauerfirst13 = M.last14 = Hewettfirst14 = P. C.last15 = Beersfirst15 = T. C.last16 = Bellfirst16 = E. F.last17 = Grebelfirst17 = E. K.last18 = Schneiderfirst18 = D. P.last19 = Newbergfirst19 = H. J.last20 = Wysefirst20 = R. F. G.last21 = Rockosifirst21 = C. M.author-link21=Constance M. Rockosilast22 = Yannyfirst22 = B.last23 = Luptonfirst23 = R.last24 = Smithfirst24 = J. A.last25 = Barentinefirst25 = J. C.last26 = Brewingtonfirst26 = H.last27 = Brinkmannfirst27 = J.last28 = Harvanekfirst28 = M.last29 = Kleinmanfirst29 = S. J.last30 = Krzesinskifirst30 = J.title = A New Milky Way Dwarf Satellite in Canes Venaticijournal = The Astrophysical Journalvolume = 643issue = 2pages = L103year = 2006arxiv = astro-ph/0604354bibcode = 2006ApJ...643L.103Zs2cid = 119421888 }}
Andromeda IIIdE2AndromedaSatellite of the Andromeda Galaxy
NGC 185dE3 pecCassiopeiaSatellite of the Andromeda Galaxy
Andromeda IdE3 pecAndromedaSatellite of the Andromeda Galaxy
Sculptor Dwarf (E351-G30)dE3SculptorSatellite of Milky Way
Andromeda V (UKS 4977-94)dSphAndromedaSatellite of the Andromeda Galaxy
Andromeda II (NCA 14)dE0AndromedaSatellite of the Andromeda Galaxy
Fornax Dwarf (E356-G04)dSph/E2FornaxSatellite of Milky Way
Carina Dwarf (E206-G220)dE3CarinaSatellite of Milky Way
Leo I (DDO 74)dE3LeoSatellite of Milky Way
Sextans Dwarf (Sextans 1)dE3SextansSatellite of Milky Way
Leo II (Leo B)dE0 pecLeoSatellite of Milky Way
Ursa Minor Dwarf (NCA 47-49)dE4Ursa MinorSatellite of Milky Way
Draco Dwarf (DDO 208)dE0 pecDracoSatellite of Milky Way
SagDSG (Sagittarius Dwarf Spheroidal Galaxy)dSph/E7SagittariusSatellite of Milky Way
Tucana DwarfdE5Tucana3.2 million ly away
Cassiopeia Dwarf (Andromeda VII, NCA 4)dSphCassiopeiaSatellite of the Andromeda Galaxy
Pegasus Dwarf Spheroidal Galaxy (Andromeda VI)dSphPegasusSatellite of the Andromeda Galaxy
Ursa Major I DwarfdSphUrsa MajorSatellite of the Milky Way
Ursa Major II DwarfdSphUrsa MajorSatellite of the Milky Way
Ursa Major IIIdSphUrsa MajorSatellite of the Milky Way
Leo IVdSphLeoSatellite of the Milky Way
Leo VdSphLeoSatellite of the Milky Way
Leo TdSph/IrrLeoSatellite of the Milky Way
Boötes IIdSphBoötesSatellite of the Milky Way
Boötes III (NCA 4.9)dSphBoötesSatellite of the Milky Way, Bootes lll likely formed both the Bootes Ill Stream & the Monosoros Stellar stream
Boötes IVdSphBoötesSatellite of the Milky Way
Coma BerenicesdSphComa BerenicesSatellite of the Milky Way
Segue 2 (Aries Dwarf, NCA 429)dSphAriesSatellite of the Milky Way
Hercules (NCA 4977429)dSphHerculesSatellite of the Milky Way
Pisces IIdSphPiscesSatellite of the Milky Way
Reticulum IIdSphReticulumSatellite of the Milky Way
Reticulum IIIdSphReticulumSatellite of the Milky Way
Eridanus IIdSphEridanusProbable satellite of the Milky Way
Grus IdSphGrusSatellite of the Milky Way
Grus IIdSphGrusSatellite of the Milky Way
Tucana IIdSphTucanaSatellite of the Milky Way
Hydrus I (Hydrus Dwarf spheroidal galaxy)dSphHydrusSatellite of the Milky Way
Draco IIdSphDracoSatellite of the Milky Way
Carina IIIdSphCarinaSatellite of the Milky Way
Triangulum II (Laevens 2)dSphTriangulumSatellite of the Milky Way
Carina IIdSphCarinaSatellite of the Milky Way
Pictor IIdSphPictorSatellite of the Milky Way
Horologium IIdSphHorologiumSatellite of the Milky Way
Virgo IdSphVirgoSatellite of the Milky Way
Virgo IIIdSph?Virgolast1=Hommafirst1=Daisukelast2=Chibafirst2=Masashilast3=Komiyamafirst3=Yutakalast4=Tanakafirst4=Masayukilast5=Okamotofirst5=Sakurakolast6=Tanakafirst6=Mikitolast7=Ishigakifirst7=Miho Nlast8=Hayashifirst8=Koheilast9=Arimotofirst9=Nobuolast10=Luptonfirst10=Robert Hlast11=Straussfirst11=Michael Alast12=Miyazakifirst12=Satoshilast13=Wangfirst13=Shiang-Yulast14=Murayamafirst14=Hitoshititle=Final results of the search for new Milky Way satellites in the Hyper Suprime-Cam Subaru Strategic Program survey: Discovery of two more candidatesjournal=Publications of the Astronomical Society of Japandate=2024-06-08volume=76issue=4pages=733–752issn=0004-6264doi=10.1093/pasj/psae044arxiv=2311.05439 }}
Sextans IIdSph?SextansSatellite of the Milky Way
Aquarius IIdSphAquariusSatellite of the Milky Way
Aquarius IIIdSph?AquariusSatellite of the Milky Way
Crater IIdSphCraterSatellite of the Milky Way
Hydra IIdSphHydraSatellite of the Milky Way
Antlia IIdSphAntliaSatellite of the Milky Way
Pegasus IIIdSphPegasusSatellite of the Milky Way
Pegasus IVdSphPegasusarxiv=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 }}
Pegasus WdSphPegasusRecent star formation, could still be starforming
Cetus IIIdSphCetusSatellite of the Milky Way
Leo KdSph?LeoSatellite of the Milky Way
Leo MdSph?Leodoi=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 VIdSphLeoSatellite of the Milky Way
Leo Minor IdSph?Leo Minordoi=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 }}
Boötes VdSph?BoötesSatellite of the Milky Way
Virgo IIdSph?VirgoSatellite of the Milky Way
Tucana BdSphTucana
DES 1dEPerseusSatellite of Milky Way
Antlia DwarfdE3/dSph/Irr?AntliaMember of Antlia-Sextans Group
Andromeda IXdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XIdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XIIdSphAndromedaPossible satellite of the Andromeda Galaxy
Andromeda XIII (Pisces III)dSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XIV (Pisces IV)dSphPiscesPossible satellite of the Andromeda Galaxy
Andromeda XVdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XVIIdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XIXdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XXdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XXIdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XXIIdSphPiscesPossible satellite of the Triangulum Galaxy
Andromeda XXIIIdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XXIVdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XXVdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XXVIdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XXVIIdSphAndromedaSatellite of the Andromeda Galaxy, tidally disrupted
Andromeda XXIXdSphPegasusSatellite of the Andromeda Galaxy
Andromeda XXX (Cassiopeia II)dSph?CassiopeiaSatellite of the Andromeda Galaxy
Andromeda XXXI (Lacerta I)dSph?LacertaSatellite of the Andromeda Galaxy
Andromeda XXXII (Cassiopeia III)dSph?CassiopeiaSatellite of the Andromeda Galaxy
Andromeda XXXIV (Pegasus V)dSphPegasusarxiv=2204.09068last1=Collinsfirst1=Michelle L. M.last2=Charlesfirst2=Emily J. E.last3=Martínez-Delgadofirst3=Davidlast4=Monellifirst4=Matteolast5=Karimfirst5=Noushinlast6=Donatiellofirst6=Giuseppelast7=Tollerudfirst7=Erik J.last8=Boschinfirst8=Waltertitle=Pegasus V/Andromeda XXXIV–a newly discovered ultrafaint dwarf galaxy on the outskirts of Andromedajournal=Monthly Notices of the Royal Astronomical Society: Lettersyear=2022volume=515issue=1pages=L72–L77doi=10.1093/mnrasl/slac063doi-access=freebibcode=2022MNRAS.515L..72C }}
Andromeda XXXVdSphAndromedaSatellite of the Andromeda Galaxy
Andromeda XVI (Pisces V)dSphPiscesPossible satellite of the Andromeda Galaxy
Andromeda XXVIIIdSph?PegasusPossible satellite of the Andromeda Galaxy
Andromeda XXXIII (Perseus I)dSph?PerseusPossible satellite of the Andromeda Galaxy
Andromeda XVIIIdSphAndromeda
Centaurus IdSphCentaurustitle=Two Ultra-faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Surveylast1=Maufirst1=S.display-authors=etalyear=2020journal=The Astrophysical Journalvolume=890issue=2page=136doi=10.3847/1538-4357/ab6c67arxiv=1912.03301bibcode=2020ApJ...890..136Ms2cid=208857609doi-access=free }}
Pisces VII (Triangulum III)dSph?Piscesdoi=10.1093/mnras/stab2797bibcode=2022MNRAS.509...16Marxiv=2104.03859title=Pisces VII: Discovery of a possible satellite of Messier 33 in the DESI legacy imaging surveysyear=2022last1=Martínez-Delgadofirst1=Davidlast2=Karimfirst2=Noushinlast3=Charlesfirst3=Emily J E.last4=Boschinfirst4=Walterlast5=Monellifirst5=Matteolast6=Collinsfirst6=Michelle L M.last7=Donatiellofirst7=Giuseppelast8=Alfarofirst8=Emilio J.journal=Monthly Notices of the Royal Astronomical Societyvolume=509issue=1pages=16–24doi-access=free }}
Virgo Stellar StreamdSph (remnant)?VirgoIn the process of merging with the Milky Way
Canis Major DwarfIrr?Canis MajorPossibly a dwarf galaxy in the process of merging with the Milky Way
Hydra 1HydraPossibly a dwarf galaxy in the process of merging with the Milky Way
Tucana IIIdSph or cluster?TucanaSatellite of the Milky Way, tidally disrupting
Tucana IVdSph or cluster?TucanaSatellite of the Milky Way
Tucana VdSph or cluster?TucanaPossibly non-existent
Columba IdSph or cluster?ColumbaSatellite of the Milky Way
Segue 1dSph or Globular ClusterLeoSatellite of the Milky Way
Cetus IICetusLikely part of Sagittarius tidal stream
Willman 1dSph or Globular ClusterUrsa Major147,000 light-years away
Horologium IdSph or Globular ClusterHorologiumSatellite of the Milky Way. Not to be confused with the Horologium Supercluster.
PictorisdSph or Globular ClusterPictorSatellite of the Milky Way
Phoenix IIdSph or Globular ClusterPhoenixSatellite of the Milky Way
Indus I (Kim 2, Indus Dwarf)dSph or Globular ClusterIndusSatellite of the Milky Way
Eridanus IIIdSph or Globular ClusterEridanusdoi=10.3847/1538-4357/aa9edatitle=On the Nature of Ultra-faint Dwarf Galaxy Candidates. I. DES1, Eridanus III, and Tucana Vyear=2018last1=Connfirst1=Blair C.last2=Jerjenfirst2=Helmutlast3=Kimfirst3=Dongwonlast4=Schirmerfirst4=Mischajournal=The Astrophysical Journalvolume=852issue=2page=68arxiv=1712.01439bibcode=2018ApJ...852...68Cs2cid=119457824doi-access=free }}
Sagittarius IIdSph or Globular ClusterSagittariusSatellite of the Milky Way
Andromeda VIII (Adsant-40-7 quote serp galaxy)dSph?AndromedaSatellite of the Andromeda Galaxy, tidally disrupting
Antlia BAntliaMember of Antlia-Sextans Group
NGC 3109 (Antlia Sextans galaxy l)SB(s)mHydraMember of Antlia-Sextans Group, it would be the 4th largest member if part of the Local Group
Mass:
Diameter (D25.5 isophote): 41,700 light-years
Andromeda IVIrrAndromedaOnce considered to be associated with M31. Its distance is now known to be 22 to 24 million light years (not close to the Andromeda Galaxy at all).
GR 8 (DDO 155)Im VVirgolast=Tolstoy, Elinetitle=The stellar content of Local Group galaxies, Proceedings of the 192nd symposium of the International Astronomical Unionpublisher=Astronomical Society of the Pacificyear=1999isbn=978-1886733824editor=Patricia Whitelockeditor2=Russell Cannonvolume=192pages=218chapter=Detailed Star-Formation Histories of Nearby Dwarf Irregular Galaxies using HSTbibcode=1999IAUS..192..218T}}
IC 5152 (Indus III)IAB(s)m IVInduslast1=Ziljstra, A. A.last2=Minniti, Dantedate=April 1999title=A Dwarf Irregular Galaxy at the Edge of the Local Group: Stellar Populations and Distance of IC 5152journal=Astronomical Journalvolume=117issue=4pages=1743–1757arxiv=astro-ph/9812330bibcode=1999AJ....117.1743Zdoi=10.1086/300802s2cid=14737502 }}
KK 153Ursa Majordoi=10.3847/2041-8213/adbe7edoi-access=freetitle=FAST Discovery of a Gas-rich and Ultrafaint Dwarf Galaxy: KK153date=2025last1=Xufirst1=Jin-Longlast2=Zhufirst2=Minglast3=Yufirst3=Nai-Pinglast4=Zhangfirst4=Chuan-Penglast5=Liufirst5=Xiao-Lanlast6=Aifirst6=Meilast7=Jiangfirst7=Pengjournal=The Astrophysical Journal Lettersvolume=982issue=2pages=L36arxiv=2503.08999bibcode=2025ApJ...982L..36X }}
NGC 300SA(s)dSculptorDistance 6.07 million light years
NGC 55SB(s)mSculptorDistance 6.5 million light years
NGC 404E0 or SA(s)0−Andromedalast1=Jensen, Joseph B.last2=Tonry, John L.last3=Barris, Brian J.last4=Thompson, Rodger I.last5=Liu, Michael C.last6=Rieke, Marcia J.last7=Ajhar, Edward A.last8=Blakeslee, John P.display-authors=4date=February 2003title=Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuationsjournal=Astrophysical Journalvolume=583issue=2pages=712–726arxiv=astro-ph/0210129bibcode=2003ApJ...583..712Jdoi=10.1086/345430s2cid=551714 }}
NGC 1569 (IC 49447)Irp+ III-IVCamelopardalislast1=Grocholski, Aaron J.last2=Aloisi, Alessandralast3=van der Marel, Roeland P.last4=Mack, Jenniferlast5=Annibali, Francescalast6=Angeretti, Lucalast7=Greggio, Lauralast8=Held, Enrico V.last9=Romano, Donatellalast10=Sirianni, Marcolast11=Tosi, Monicadisplay-authors=4name-list-style=ampdate=20 October 2008title=A New Hubble Space Telescope Distance to NGC 1569: Starburst Properties and IC 342 Group Membershipjournal=Astrophysical Journal Lettersvolume=686issue=2pages=L79–L82arxiv=0808.0153bibcode=2008ApJ...686L..79Gdoi=10.1086/592949s2cid=9877496 }}
NGC 1560 (IC 2062)SdCamelopardalisDistance 8-12 million light years
Camelopardalis AIrrCamelopardalistitle=Cosmicflows-2: The Dataauthor1=Tully, R. Brentdisplay-authors=etaljournal=The Astronomical Journalvolume=146issue=4date=2013bibcode=2013AJ....146...86Tdoi=10.1088/0004-6256/146/4/86arxiv=1307.7213page=86s2cid=118494842}}
Argo DwarfIrrCarina7.1 million light-years away
ESO 347-8 (2318–42, PGC 475744)IrrGrus9 million light-years away fairly isolated until million light years. away from the galaxy
UKS 2323-326 (ESO 407-18)IrrSculptorDistance 7.2 million light-years
UGC 9128 (DDO 187)Irp+Boötes7 million light-years away
KKs 3 (Hydrus II)dSphHydrusDistance 5.2 million light-years
Palomar 12 (Capricornus Dwarf)dSphrCapricornusGlobular cluster formerly classified as a dwarf spheroidal galaxy
Palomar 4 (Ursa Major Dwarf)d SphrUrsa MajorGlobular cluster formerly classified as a dwarf spheroidal galaxy
Palomar 5 (Serpens Dwarf)SerpensGlobular cluster formerly classified as a dwarf spheroidal galaxy
Palomar 3 (Sextans C)SculptorGlobular cluster formerly classified as a dwarf spheroidal galaxy
Segue 3Pegasuslast1 = Fadelyfirst1 = R.last2 = Willmanfirst2 = B.last3 = Gehafirst3 = M.author3-link= Marla Gehalast4 = Walshfirst4 = S.last5 = Muñozfirst5 = R. R.last6 = Jerjenfirst6 = H.last7 = Vargasfirst7 = L. C.last8 = Da Costafirst8 = G. S.doi = 10.1088/0004-6256/142/3/88title = Segue 3: An old, extremely low luminosity star cluster in the Milky Way's halojournal = The Astronomical Journalvolume = 142issue = 3pages = 88year = 2011arxiv = 1107.3151bibcode = 2011AJ....142...88Fs2cid = 118509282 }}
Laevens 1 (Crater Dwarf)Cratertitle=Probing the boundary between star clusters and dwarf galaxies: A MUSE view on the dynamics of Crater/Laevens Ifirst1=Karinalast1=Voggelfirst2=Michaellast2=Hilkerfirst3=Holgerlast3=Baumgardtfirst4=Michelle L.M.last4=Collinsfirst5=Eva K.last5=Grebelfirst6=Berndlast6=Husemannfirst7=Tomlast7=Richtlerfirst8=Matthias J.last8=Frankarxiv=1604.06806doi=10.1093/mnras/stw1132volume=460journal=Monthly Notices of the Royal Astronomical Societyyear=2016issue=3pages=3384–3397doi-access=freebibcode = 2016MNRAS.460.3384V }}
DES J2038-4609 (Indus II)IndusLikely a chance alignment of stars

Structure

Overview of the structure and trajectory of the Local Group

Streams

  • Magellanic Stream, a stream of gas being stripped off the Magellanic Clouds due to their interaction with the Milky Way
  • Monoceros Ring, a ring of stars around the Milky Way that is proposed to consist of a stellar stream torn from the Canis Major Dwarf Galaxy
  • Virgo Stream, a stream formed from a dwarf galaxy.
  • Helmi Stream

Future

The galaxies of the Local Group are likely to merge together under their own mutual gravitational attractions over a timescale of tens of billions of years into a single elliptical galaxy, with the coalescence of Andromeda and the Milky Way being the predominant event in this process.{{cite journal There is debate over whether ellipticity might be the immediate structure of the combined galaxy right after the collision or whether ellipticity might only emerge after a theoretical intermediate period of retaining a spiraling structure directly following the collision. Some even theorize a permanent superspiral or a transition toward a more lenticular galaxy, rather than a more elliptical or spiraled distribution, as the future of the Local Group's galactic merger.

Location

Main article: Laniakea Supercluster

References

References

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  11. (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.
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  21. (2006). "A New Milky Way Dwarf Satellite in Canes Venatici". The Astrophysical Journal.
  22. (2008). "A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites". The Astrophysical Journal.
  23. (2024-06-08). "Final results of the search for new Milky Way satellites in the Hyper Suprime-Cam Subaru Strategic Program survey: Discovery of two more candidates". Publications of the Astronomical Society of Japan.
  24. (2025). "Discovery and Spectroscopic Confirmation of Aquarius III: A Low-mass Milky Way Satellite Galaxy". The Astrophysical Journal.
  25. (2023). "Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus". The Astrophysical Journal.
  26. (2024). "Discovery and Characterization of Two Ultrafaint Dwarfs outside the Halo of the Milky Way: Leo M and Leo K". The Astrophysical Journal.
  27. (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.
  28. (2023). "Six More Ultra-faint Milky Way Companions Discovered in the DECam Local Volume Exploration Survey". The Astrophysical Journal.
  29. (2022). "Tucana B: A Potentially Isolated and Quenched Ultra-faint Dwarf Galaxy at D ≈ 1.4 MPC". The Astrophysical Journal Letters.
  30. (2019). "A dwarf disrupting - Andromeda XXVII and the North West Stream". Monthly Notices of the Royal Astronomical Society.
  31. (2022). "Pegasus V/Andromeda XXXIV–a newly discovered ultrafaint dwarf galaxy on the outskirts of Andromeda". Monthly Notices of the Royal Astronomical Society: Letters.
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  39. (2025). "FAST Discovery of a Gas-rich and Ultrafaint Dwarf Galaxy: KK153". The Astrophysical Journal Letters.
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  41. (20 October 2008). "A New Hubble Space Telescope Distance to NGC 1569: Starburst Properties and IC 342 Group Membership". Astrophysical Journal Letters.
  42. (2013). "Cosmicflows-2: The Data". The Astronomical Journal.
  43. "Pal3".
  44. (2011). "Segue 3: An old, extremely low luminosity star cluster in the Milky Way's halo". The Astronomical Journal.
  45. (2016). "Probing the boundary between star clusters and dwarf galaxies: A MUSE view on the dynamics of Crater/Laevens I". Monthly Notices of the Royal Astronomical Society.
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