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The Local Group
Local Group
is the galaxy group that includes the Milky Way. The Local Group
Local Group
comprises more than 54 galaxies, most of them dwarf galaxies. Its gravitational center is located somewhere between the Milky Way
Milky Way
and the Andromeda Galaxy. The Local Group
Local Group
has a diameter of 10 Mly (3.1 Mpc) (about 1023 meters) and has a binary (dumbbell)[1] distribution. The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster. The three largest members of the group (in decreasing order) are the Andromeda Galaxy, the Milky Way[2] and the Triangulum
Triangulum
Galaxy. The larger two of these spiral galaxies each have their own system of satellite galaxies.

The Andromeda Galaxy's satellite system consists of Messier 32
Messier 32
(M32), Messier 110
Messier 110
(M110), NGC 147, NGC 185, Andromeda I
Andromeda I
(And I), And II, And III, And V, And VI (also known as Pegasus Dwarf Spheroidal Galaxy, or Pegasus DSph), And VII (also known as Cassiopeia Dwarf
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.[citation needed] Milky Way's satellite galaxies system comprises 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
Draco Dwarf
Galaxy, Carina Dwarf
Carina Dwarf
Galaxy, Sextans
Sextans
Dwarf Galaxy, Sculptor
Sculptor
Dwarf Galaxy, Fornax Dwarf
Fornax Dwarf
Galaxy, Leo I (a dwarf galaxy), Leo II (a dwarf galaxy), and Ursa Major I Dwarf Galaxy and Ursa Major II Dwarf Galaxy, plus several additional ultra-faint dwarf spheroidal galaxies.[3] The Triangulum Galaxy
Triangulum Galaxy
may or may not be a companion to the Andromeda Galaxy. Pisces Dwarf
Pisces Dwarf
Galaxy is equidistant from the Andromeda Galaxy and the Triangulum
Triangulum
Galaxy, so it may be a satellite of either.[4] The membership of NGC 3109, with its companions Sextans A
Sextans A
and the Antlia Dwarf
Antlia Dwarf
Galaxy, is uncertain due to extreme distances from the center of the Local Group.[citation needed] The other members of the group are likely gravitationally secluded from these large subgroups: IC 10, IC 1613, Phoenix Dwarf
Phoenix Dwarf
Galaxy, Leo A, Tucana Dwarf
Tucana Dwarf
Galaxy, Cetus Dwarf Galaxy, Pegasus Dwarf Irregular Galaxy, Wolf–Lundmark–Melotte, Aquarius Dwarf
Aquarius Dwarf
Galaxy, and Sagittarius Dwarf Irregular Galaxy.[citation needed]

Contents

1 History 2 Component galaxies

2.1 Map 2.2 List of galactic bodies

3 Other objects 4 See also 5 References 6 External links

History[edit] The term "The Local Group" was introduced by Edwin Hubble
Edwin Hubble
in Chapter VI of his 1936 book The Realm of the Nebulae.[5] 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
IC 1613
and NGC 147. He also identified IC 10
IC 10
as a possible part of Local Group. By 2003, the number of known Local Group
Local Group
members had increased from his initial 12 to 36.[6] Component galaxies[edit] Map[edit]

Local Group
Local Group
(clickable map)

List of galactic bodies[edit]

Spiral galaxies

name type constellation notes

Andromeda Galaxy
Andromeda Galaxy
(M31, NGC 224) SA(s)b Andromeda ~220 kly in diameter, it is the largest and most massive galaxy in the group.

Milky Way SBbc Sagittarius (centre) As large as Andromeda galaxy, between 150 and 180kly, home 500-580 billion stars .[7][8]

Triangulum Galaxy
Triangulum Galaxy
(M33, NGC 598) SA(s)cd Triangulum Third largest, only unbarred spiral galaxy and possible satellite of the Andromeda Galaxy. Triangulum Galaxy
Triangulum Galaxy
has mass of ~50 billion solar masses and is Home to ~60 billion stars.

Elliptical galaxies

name type constellation notes

M32 (NGC 221) E2 Andromeda satellite of the Andromeda Galaxy

Irregular galaxies

name type constellation notes

Wolf–Lundmark–Melotte
Wolf–Lundmark–Melotte
(WLM, DDO 221) Ir+ Cetus

IC 10 KBm or Ir+ Cassiopeia

Small Magellanic Cloud
Small Magellanic Cloud
(SMC, NGC 292) SB(s)m pec Tucana satellite of Milky Way, 6th largest galaxy in the local group with mass of between 7.5 and 8 billion solar mass.

Canis Major
Canis Major
Dwarf Irr Canis Major satellite of Milky Way

Pisces Dwarf
Pisces Dwarf
(LGS3) Irr Pisces satellite of the Triangulum
Triangulum
Galaxy?

IC 1613
IC 1613
(UGC 668) IAB(s)m V Cetus

Phoenix Dwarf Irr Phoenix

Large Magellanic Cloud
Large Magellanic Cloud
(LMC) Irr/SB(s)m Dorado Fourth largest member of the group, satellite of Milky Way, mass between 10 and 85 billion solar masses. Recent finding puts it at 10% mass of Milky Way
Milky Way
Galaxy. [9]

Leo A
Leo A
(Leo III) IBm V Leo

Sextans B
Sextans B
(UGC 5373) Ir+IV-V Sextans

NGC 3109 Ir+IV-V Hydra

Sextans A
Sextans A
(UGCA 205) Ir+V Sextans

Aquarius Dwarf
Aquarius Dwarf
(DDO 210) IB(s)m Aquarius Distance 3.2 million light years. Quite isolated in space, membership to Local Group
Local Group
established in 1999[10]

Dwarf elliptical galaxies

name type constellation notes

M110 (NGC 205) dE6p Andromeda satellite of the Andromeda Galaxy
Andromeda Galaxy
and 5th largest galaxy with the mass of 9.3 solar masses.

NGC 147
NGC 147
(DDO 3) dE5 pec Cassiopeia satellite of the Andromeda Galaxy

SagDIG
SagDIG
(Sagittarius Dwarf Irregular Galaxy) IB(s)m V Sagittarius Most remote from barycenter member thought to be in the Local Group.[10]

NGC 6822
NGC 6822
(Barnard's Galaxy) IB(s)m IV-V Sagittarius

Pegasus Dwarf (Pegasus Dwarf Irregular, DDO 216) Irr Pegasus

Dwarf spheroidal galaxies

name type constellation notes

Boötes
Boötes
I dSph Boötes

Cetus
Cetus
Dwarf dSph/E4 Cetus

Canes Venatici
Canes Venatici
I Dwarf and Canes Venatici
Canes Venatici
II Dwarf dSph Canes Venatici

KKs 3 dSph

Andromeda III dE2 Andromeda satellite of the Andromeda Galaxy

NGC 185 dE3 pec Cassiopeia satellite of the Andromeda Galaxy

Andromeda I dE3 pec Andromeda satellite of the Andromeda Galaxy

Sculptor
Sculptor
Dwarf (E351-G30) dE3 Sculptor satellite of Milky Way

Andromeda V dSph Andromeda satellite of the Andromeda Galaxy

Andromeda II dE0 Andromeda satellite of the Andromeda Galaxy

Fornax Dwarf
Fornax Dwarf
(E356-G04) dSph/E2 Fornax satellite of Milky Way

Carina Dwarf
Carina Dwarf
(E206-G220) dE3 Carina satellite of Milky Way

Antlia
Antlia
Dwarf dE3/dSph/Irr? Antlia

Leo I (DDO 74) dE3 Leo satellite of Milky Way

Sextans
Sextans
Dwarf dE3 Sextans satellite of Milky Way

Leo II (Leo B) dE0 pec Leo satellite of Milky Way

Ursa Minor
Ursa Minor
Dwarf dE4 Ursa Minor satellite of Milky Way

Draco Dwarf
Draco Dwarf
(DDO 208) dE0 pec Draco satellite of Milky Way

SagDSG (Sagittarius Dwarf Spheroidal Galaxy) dSph/E7 Sagittarius satellite of Milky Way

Tucana
Tucana
Dwarf dE5 Tucana

Cassiopeia Dwarf
Cassiopeia Dwarf
(Andromeda VII) dSph Cassiopeia satellite of the Andromeda Galaxy

Pegasus Dwarf Spheroidal Galaxy (Andromeda VI) dSph Pegasus satellite of the Andromeda Galaxy

Ursa Major I Dwarf and Ursa Major
Ursa Major
II Dwarf dSph Ursa Major satellite of Milky Way

Leo IV dSph Leo satellite of the Milky Way

Leo V dSph Leo satellite of the Milky Way

Leo T dSph/Irr Leo satellite of the Milky Way

Boötes
Boötes
II dSph Boötes satellite of the Milky Way

Boötes
Boötes
III dSph Boötes satellite of the Milky Way

Coma Berenices dSph Coma Berenices satellite of the Milky Way

Segue 2 dSph Aries satellite of the Milky Way

Hercules dSph Hercules satellite of the Milky Way

Pisces II dSph Pisces satellite of the Milky Way

Reticulum
Reticulum
II dSph Reticulum satellite of the Milky Way

Eridanus II dSph Eridanus probable satellite of the Milky Way

Grus dSph Grus satellite of the Milky Way

Tucana
Tucana
II dSph Tucana satellite of the Milky Way

Identification unclear

name type constellation notes

Virgo Stellar Stream dSph (remnant)? Virgo In the process of merging with the Milky Way

Willman 1 dSph or Globular Cluster Ursa Major 147,000 light-years away

UGCA 86 (0355+66) Irr, dE or S0 Camelopardalis

UGCA 92 (EGB0427+63) Irr or S0 Camelopardalis

Horologium dSph or Globular Cluster Horologium satellite of the Milky Way. Not to be confused with the Horologium Supercluster.

Pictoris dSph or Globular Cluster Pictor satellite of the Milky Way

Phoenix II dSph or Globular Cluster Phoenix satellite of the Milky Way

Indus dSph or Globular Cluster Indus satellite of the Milky Way

Eridanus III dSph or Globular Cluster Eridanus satellite of the Milky Way

Probable non-members

name type constellation notes

GR 8 (DDO 155) Im V Virgo Distance 7.9 million light years[11]

IC 5152 IAB(s)m IV Indus Distance 5.8 million light years, possibly an outlying member of the local group[12]

NGC 55 SB(s)m Sculptor Distance 7.2 million light years[13]

NGC 404 E0 or SA(s)0− Andromeda Distance 10 million light years[14]

Andromeda IV Irr Andromeda Once 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).[15]

NGC 1569 Irp+ III-IV Camelopardalis In IC 342
IC 342
group of galaxies. Distance 11 million light years[16]

NGC 1560 (IC 2062) Sd Camelopardalis Distance 8-12 million light years

Camelopardalis
Camelopardalis
A Irr Camelopardalis

Argo Dwarf Irr Carina

ESO 347-8 (2318–42) Irr Grus

UKS 2323-326 Irr Sculptor

UGC 9128 (DDO 187) Irp+ Boötes

Objects in the Local Group
Local Group
no longer recognised as galaxies

name type constellation notes

Palomar 12
Palomar 12
( Capricornus
Capricornus
Dwarf)

Capricornus a globular cluster formerly classified as a dwarf spheroidal galaxy

Palomar 4
Palomar 4
( Ursa Major
Ursa Major
Dwarf)

Ursa Major a globular cluster formerly classified as a dwarf spheroidal galaxy

Palomar 3 ( Sextans
Sextans
C)

Sculptor a globular cluster formerly classified as a dwarf spheroidal galaxy[17]

Other objects[edit]

Smith's Cloud, a high-velocity cloud, between 32,000 and 49,000 light years from Earth[18] and 8,000 light years from the disk of the Milky Way galaxy[19] HVC 127-41-330, a high-velocity cloud, 2.3 million light-years from Earth Monoceros Ring, a ring of stars around the Milky Way
Milky Way
that is proposed to consist of a stellar stream torn from the Canis Major
Canis Major
Dwarf Galaxy

A diagram of our location in the observable universe. (Click here for larger image.)

See also[edit]

Cosmology portal

Galaxy cluster List of nearest galaxies List of galaxy clusters IC 342/Maffei Group, the group of galaxies nearest to the Local Group. Local Supercluster List of Andromeda's satellite galaxies List of Milky Way's satellite galaxies

References[edit]

^ Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6.  ^ "The Local Group". NASA's High Energy Astrophysics Science Archive Research Center (HEASARC). NASA. Retrieved 2015-05-05.  ^ 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:1503.02079 . Bibcode:2015ApJ...805..130K. doi:10.1088/0004-637X/805/2/130.  ^ Miller, Bryan W.; et al. (December 2001), "The Star Formation History of LGS 3", The Astrophysical Journal, 562 (2): 713–726, arXiv:astro-ph/0108408 , Bibcode:2001ApJ...562..713M, doi:10.1086/323853  ^ Hubble, E.P. (1936). The realm of the nebulae. Mrs. Hepsa Ely Silliman memorial lectures, 25. New Haven: Yale University Press. ISBN 9780300025002. OCLC 611263346. Archived from the original on 2012-09-29. (pp. 124–151) ^ van den Bergh, Sidney (May 2003). "History of the Local Group". To be published in: "The Local Group
Local Group
as an Astrophysical Laboratory". Cambridge University Press: 5042. arXiv:astro-ph/0305042 . Bibcode:2003astro.ph..5042V.  ^ http://www.atlasoftheuniverse.com/galaxies.html ^ https://arxiv.org/abs/1503.00257 ^ http://www.cam.ac.uk/research/news/a-bridge-of-stars-connects-two-dwarf-galaxies ^ a b van den Bergh, Sidney (April 2000). "Updated Information on the Local Group". The Publications of the Astronomical Society of the Pacific. 112 (770): 529–536. arXiv:astro-ph/0001040 . Bibcode:2000PASP..112..529V. doi:10.1086/316548.  ^ Tolstoy, Eline (1999). "Detailed Star-Formation Histories of Nearby Dwarf Irregular Galaxies using HST". In Patricia Whitelock and Russell Cannon. The stellar content of Local Group
Local Group
galaxies, Proceedings of the 192nd symposium of the International Astronomical Union. Astronomical Society of the Pacific. p. 218. Bibcode:1999IAUS..192..218T. ISBN 1886733821. CS1 maint: Uses editors parameter (link) ^ Ziljstra, A. A.; Minniti, Dante (April 1999). "A Dwarf Irregular Galaxy at the Edge of the Local Group: Stellar Populations and Distance of IC 5152". Astronomical Journal. 117 (4): 1743–1757. arXiv:astro-ph/9812330 . Bibcode:1999AJ....117.1743Z. doi:10.1086/300802. Retrieved 2011-03-11.  ^ van de Steene, G. C.; et al. (2006). "Distance determination to NGC 55 from the planetary nebula luminosity function". Astronomy and Astrophysics. 455 (3): 891–896. Bibcode:2006A&A...455..891V. doi:10.1051/0004-6361:20053475.  ^ Jensen, Joseph B.; Tonry, John L.; Barris, Brian J.; Thompson, Rodger I.; et al. (February 2003). "Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations". Astrophysical Journal. 583 (2): 712–726. arXiv:astro-ph/0210129 . Bibcode:2003ApJ...583..712J. doi:10.1086/345430.  ^ Nowakowski, Tomasz (22 December 2015). " Andromeda IV
Andromeda IV
turns out to be a solitary gas-rich dwarf galaxy". physorg. Retrieved 25 December 2015.  ^ Grocholski, Aaron J.; Aloisi, Alessandra; van der Marel, Roeland P.; Mack, Jennifer; et al. (October 20, 2008). "A New Hubble Space Telescope Distance to NGC 1569: Starburst Properties and IC 342
IC 342
Group Membership". Astrophysical Journal Letters. 686 (2): L79–L82. arXiv:0808.0153 . Bibcode:2008ApJ...686L..79G. doi:10.1086/592949.  ^ "Pal3". simbad.u-strasbg.fr. Retrieved 26 August 2017.  ^ Wakker, B. P.; York, D. G.; Wilhelm, R.; Barentine, J. C.; Richter, P.; Beers, T. C.; Ivezić, Ž.; Howk, J. C. (2008). "Distances to Galactic High‐Velocity Clouds. I. Cohen Stream, Complex GCP, Cloud g1". The Astrophysical Journal. 672 (1): 298–319. arXiv:0709.1926 . Bibcode:2008ApJ...672..298W. doi:10.1086/523845.  ^ "Massive Gas Cloud Speeding Toward Collision With Milky Way". Retrieved 2008-06-06. 

External links[edit]

Wikimedia Commons has media related to Local Group.

The Local Group
Local Group
of Galaxies, SEDS Messier pages A Survey of the Resolved Stellar Content of Nearby Galaxies Currently Forming Stars, Lowell Observatory van den Bergh, Sidney (2000). "Updated Information on the Local Group". The Publications of the Astronomical Society of the Pacific. 112 (770): 529–536. arXiv:astro-ph/0001040 . Bibcode:2000PASP..112..529V. doi:10.1086/316548. 

v t e

The Milky Way

Location

Milky Way → Milky Way
Milky Way
subgroup → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe Each arrow (→) may be read as "within" or "part of".

Galactic core

Center of the Milky Way Sagittarius A Sagittarius A* Supermassive black hole

Spiral arms

Carina–Sagittarius Norma–Cygnus Orion–Cygnus Perseus Scutum–Centaurus

Satellite galaxies

Magellanic Clouds

Large Magellanic Cloud Small Magellanic Cloud Magellanic Stream Magellanic Bridge

Sagittarius Spheroidal

Sagittarius Stream Boötes
Boötes
II Coma Berenices Messier 54 Palomar 12 Segue 1 Segue 2 Terzan 7

Dwarfs

Boötes
Boötes
I Boötes
Boötes
III Canes Venatici
Canes Venatici
I Canes Venatici
Canes Venatici
II Canis Major Carina Crater 2 Draco Fornax Hercules Leo I Leo II Leo IV Leo V Leo T Phoenix Pisces I Pisces II Sculptor Sextans Triangulum
Triangulum
II Ursa Major
Ursa Major
I Ursa Major
Ursa Major
II Ursa Minor Virgo I

Other

Monoceros Ring Virgo Stream Koposov I Koposov II Segue 3 Willman 1

Related

Andromeda– Milky Way
Milky Way
collision

Astronomy portal

v t e

Andromeda Galaxy

Location

Andromeda Galaxy→Andromeda subgroup → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe Each  → may be read as "within" or "part of".

Satellite galaxies

M32 M110 NGC 185 NGC 147 Andromeda I Andromeda II Andromeda III Andromeda IV* Andromeda V Andromeda VI Andromeda VII Andromeda VIII Andromeda IX Andromeda X Andromeda XI Andromeda XII Andromeda XIII Andromeda XIV Andromeda XV Andromeda XVI Andromeda XVII Andromeda XVIII Andromeda XIX Andromeda XX Andromeda XXI Andromeda XXII Andromeda XXIII Andromeda XXIV Andromeda XXV Andromeda XXVI Andromeda XXVII Andromeda XXVIII Andromeda XXIX Triangulum
Triangulum
Galaxy*

*It is uncertain whether it is a companion galaxy of the Andromeda Galaxy

Catalogued stars

AE Andromedae M31-RV

Other

Andromeda– Milky Way
Milky Way
collision S Andromedae Mayall II NGC 206

v t e

Triangulum
Triangulum
Galaxy

Location

Triangulum
Triangulum
Galaxy→ Triangulum
Triangulum
subgroup→ Local Group→ Virgo Supercluster→ Laniakea Supercluster→ Observable universe→ Universe Each → may be read as "within" or "part of".

H II regions

NGC 588 NGC 595 NGC 604

Suspected satellite galaxies

Pisces Dwarf Andromeda II

Other

Triangulum Galaxy
Triangulum Galaxy
in fiction

v t e

Earth's location in the Universe

Included

Earth → Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way
Milky Way
subgroup → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe Each arrow (→) may be read as "within" or "part of".

Related

"Cosmic View" (1957 essay) To the Moon and Beyond (1964 film) Cosmic Zoom (1968 film) Powers of Ten (1968 and 1977 films) Cosmic Voyage
Cosmic Voyage
(1996 documentary) Cosmic Eye (2012)

Astronomy portal - Cosmology portal

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WorldCat Identities VIAF: 234195301 GND: 4168105-8 SUDOC: 050418076 BNF: cb1351