Editing Dwarf galaxy

{{short description|Small galaxy composed of up to several billion stars}}
[[File:Large.mc.arp.750pix.jpg|thumb|upright=1.4|The [[Large Magellanic Cloud]], a satellite galaxy of the [[Milky Way]]]]
{{Use dmy dates|date=March 2014}}

A '''dwarf galaxy''' is a small [[galaxy]] composed of about 1000 up to several billion [[star]]s, as compared to the [[Milky Way]]'s 200–400 billion stars.<ref>{{Cite web |title=The Milky Way Galaxy |url=http://www.messier.seds.org/more/mw.html |access-date=2023-06-22 |website=www.messier.seds.org}}</ref> The [[Large Magellanic Cloud]], which closely orbits the Milky Way and contains over 30 billion stars,<ref>{{Cite web |date=2021-12-08 |title=The Magellanic Clouds, our galactic neighbors |url=https://earthsky.org/clusters-nebulae-galaxies/magellanic-clouds-large-small/ |access-date=2023-06-22 |website=earthsky.org |language=en-US}}</ref> is sometimes classified as a dwarf galaxy; others consider it a full-fledged galaxy. Dwarf galaxies' formation and activity are thought to be heavily influenced by interactions with larger galaxies. Astronomers identify numerous types of dwarf galaxies, based on their shape and composition.

== Formation ==
[[File:NGC 5264 HST.jpg|thumb|Dwarf galaxies like [[NGC 5264]] typically possess around a billion stars.<ref>{{cite web|title=An irregular island|url=http://www.spacetelescope.org/images/potw1634a/|website=www.spacetelescope.org|access-date=25 August 2016}}</ref>]]
One theory states that most galaxies, including dwarf galaxies, form in association with [[dark matter]],<ref>{{Cite journal |last=O'Callaghan |first=Jonathan |date=22 May 2024 |title=Astronomers find long-missing dwarf galaxies—too many of them |journal=Science |volume=384 |issue=6698 |page=836 |doi=10.1126/science.z6r95kt}}</ref> or from gas that contains metals. However, [[NASA]]'s [[Galaxy Evolution Explorer]] [[space probe]] identified new dwarf galaxies forming out of gases  with low [[metallicity]]. These galaxies were located in the [[Leo Ring]], a cloud of [[hydrogen]] and [[helium]] around two massive galaxies in the [[constellation]] [[Leo (constellation)|Leo]].<ref>
{{cite web
 |date=19 February 2009
 |title=New Recipe For Dwarf Galaxies: Start With Leftover Gas
 |url=https://www.sciencedaily.com/releases/2009/02/090218132145.htm
 |work=[[Science Daily]]
 |access-date=2015-07-29
}}</ref>

Because of their small size, dwarf galaxies have been observed being pulled toward and [[Interacting galaxy|ripped]] by neighbouring [[Spiral galaxy|spiral galaxies]], resulting in [[List of stellar streams|stellar streams]] and eventually [[galaxy merger]].<ref>
{{cite web
 |last=Jaggard |first=V.
 |date=9 September 2010
 |title=Pictures: New Proof Spiral Galaxies Eat, Digest Dwarfs
 |url=http://news.nationalgeographic.com/news/2010/09/photogalleries/100909-spiral-galaxies-eat-dwarf-space-science-pictures/
 |archive-url=https://web.archive.org/web/20100912161830/http://news.nationalgeographic.com/news/2010/09/photogalleries/100909-spiral-galaxies-eat-dwarf-space-science-pictures/
 |url-status=dead
 |archive-date=12 September 2010
 |publisher=[[National Geographic Society]]
 |access-date=2012-02-11
}}</ref>

==Local dwarf galaxies==
[[File:An explosive phoenix - Phoenix Dwarf.jpg|thumb|The [[Phoenix Dwarf|Phoenix Dwarf Galaxy]] is a dwarf irregular galaxy, featuring younger stars in its inner regions and older ones at its outskirts.<ref>
{{cite web
 |date=24 October 2011
 |title=Hubble Sizes up a Dwarf Galaxy
 |url=http://spacetelescope.org/images/potw1143a/
 |publisher=[[European Space Agency|ESA]]/[[Hubble Space Telescope|Hubble]]
 |access-date=2011-10-25
}}</ref>]]

There are many dwarf galaxies in the [[Local Group]]; these small galaxies frequently orbit larger galaxies, such as the [[Milky Way]], the [[Andromeda Galaxy]] and the [[Triangulum Galaxy]]. A 2007 paper<ref>
{{cite journal
 |last1=Metz |first1=M.
 |last2=Kroupa |first2=P.
 |date=2007
 |title=Dwarf-spheroidal satellites: are they of tidal origin?
 |journal=[[Monthly Notices of the Royal Astronomical Society]]
 |volume=376 |issue=1 |pages=387–392
 |arxiv=astro-ph/0701289
 |bibcode=2007MNRAS.376..387M
 |doi=10.1111/j.1365-2966.2007.11438.x
|doi-access=free
 |s2cid=16426005
 }}</ref> has suggested that many dwarf galaxies were created by [[galactic tide]]s during the early evolutions of the Milky Way and Andromeda. Tidal dwarf galaxies are produced when galaxies collide and their gravitational [[Interacting galaxy|masses interact]]. Streams of galactic material are pulled away from the parent galaxies and the halos of [[dark matter]] that surround them.<ref>
{{cite web
 |date=18 February 2009
 |title=New Recipe for Dwarf Galaxies: Start with Leftover Gas
 |url=http://newswise.com/articles/view/549307/
 |work=Newswise.com
 |access-date=2009-02-20
}}</ref> A 2018 study suggests that some local dwarf galaxies formed extremely early, during the [[Dark Ages (cosmology)|Dark Ages]] within the first billion years after the [[Big Bang]].<ref>{{cite news |last1=Rincon |first1=Paul |title=Earliest galaxies found 'on our cosmic doorstep' |url=https://www.bbc.com/news/science-environment-45198764 |access-date=17 August 2018 |work=BBC News |date=16 August 2018}}</ref>

More than 20 known dwarf galaxies orbit the Milky Way, and recent observations<ref>
{{cite journal
 |last1=Noyola |first1=E.
 |last2=Gebhardt |first2=K.
 |last3=Bergmann |first3=M.
 |year=2008
 |title=Gemini and Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in ω Centauri
 |journal=[[The Astrophysical Journal]]
 |volume=676 |issue=2 |pages=1008–1015
 |arxiv=0801.2782
 |bibcode=2008ApJ...676.1008N
 |doi=10.1086/529002
|s2cid=208867075
 }}</ref> have also led astronomers to believe the largest [[globular cluster]] in the Milky Way, [[Omega Centauri]], is in fact the core of a dwarf galaxy with a [[black hole]] at its centre, which was at some time absorbed by the Milky Way.

==Common types==
[[File:True blue.jpg|thumb|[[UGC 11411]] is a galaxy known as an irregular blue compact dwarf (BCD) galaxy.<ref>
{{cite web
 |date=15 June 2015
 |title=True blue
 |url=http://www.spacetelescope.org/images/potw1524a/
 |publisher=[[European Space Agency|ESA]]/[[Hubble Space Telescope|Hubble]]
 |access-date=2015-06-15
}}</ref>]]
* [[Elliptical galaxy]]: [[dwarf elliptical galaxy]] (dE)
* [[Dwarf spheroidal galaxy]] (dSph): Once a subtype of dwarf ellipticals, now regarded as a distinct type {{Citation needed|date=December 2021}}
* [[Irregular galaxy]]: [[Irregular galaxy#dwarf irregular anchor|dwarf irregular galaxy]] (dIrr)
* [[Spiral galaxy]]: [[dwarf spiral galaxy]] (dS) <ref name="schombertetal1995">
{{cite journal
 |last1=Schombert |first1=J.M.      |last2=Pildis |first2=R.A.
 |last3=Eder      |first3=J.A.      |last4=Oelmer |first4=A. Jr.
 |date=1995
 |title=Dwarf Spirals
 |journal=[[The Astronomical Journal]]
 |volume=110 |pages=2067–2074
 |bibcode=1995AJ....110.2067S
 |doi=10.1086/117669
|doi-access=free}}</ref>
* [[Magellanic spiral|Magellanic type dwarfs]]
* Blue compact dwarf galaxies (see [[Dwarf galaxy#Blue compact dwarf galaxies|section below]])
* Ultra-compact dwarf galaxies (see [[Dwarf galaxy#Ultra-compact dwarfs|section below]])

==Blue compact dwarf galaxies==
{{anchor|Blue compact dwarf galaxies}}
[[File:An intriguing young-looking dwarf galaxy.jpg|thumb|Blue compact dwarf [[PGC 51017]].<ref>
{{cite web
 |date=16 March 2015
 |title=An intriguing young-looking dwarf galaxy
 |url=http://www.spacetelescope.org/images/potw1511a/
 |publisher=[[European Space Agency|ESA]]/[[Hubble Space Telescope|Hubble]]
 |access-date=2015-03-21
}}</ref>]]

In [[astronomy]], a '''blue compact dwarf galaxy''' ('''BCD galaxy''') is a small galaxy which contains large [[Star cluster|clusters]] of young, hot, massive [[star]]s. These stars, the brightest of which are blue, cause the galaxy itself to appear [[blue]] in colour.<ref>
{{cite web
 |date=2 September 2011
 |title=WISE Discovers Baby Galaxies in the Nearby Universe
 |url=http://wise.ssl.berkeley.edu/sciupdates_babygalaxy.html
 |publisher=[[Wide-field Infrared Survey Explorer|WISE]]
 |access-date=2011-09-03
}}</ref> Most BCD galaxies are also classified as dwarf [[Irregular galaxy|irregular galaxies]] or as dwarf [[lenticular galaxy|lenticular galaxies]]. Because they are composed of star clusters, BCD galaxies lack a uniform shape. They consume gas intensely, which causes their stars to become very violent when forming.

BCD galaxies cool in the process of [[Star formation|forming new stars]]. The galaxies' stars are all formed at different time periods, so the galaxies have time to cool and to build up matter to form new stars. As time passes, this star formation changes the shape of the galaxies.

Nearby examples include [[NGC 1705]], [[NGC 2915]], [[NGC 3353]] and [[UGCA 281]].<ref>
{{cite journal
 |last1=López-Sánchez |first1=Á. R.
 |last2=Koribalski |first2=B.
 |last3=van Eymeren |first3=J.
 |last4=Esteban |first4=C.
 |last5=Popping |first5=A.
 |last6=Hibbard |first6=J.
 |year=2010
 |title=The environment of nearby Blue Compact Dwarf Galaxies
 |journal=[[ASP Conference Series]]
 |volume=421 |page=65
 |arxiv=0909.5500
 |bibcode=2010ASPC..421...65L
}}</ref><ref>
{{cite web
 |last=Papaderos |first=P.
 |date=7 May 2010
 |title=Blue Compact Dwarf Galaxies
 |url=http://www.observational-cosmology.eu/papaderos/Teaching/Papaderos_UCM_May2010_Lecture2.pdf
 |publisher=Centro de Astrofísica da [[Universidade do Porto]]
}}</ref><ref>
{{cite web
 |last1     = Noeske
 |first1    = K.
 |last2     = Papaderos
 |first2    = P.
 |last3     = Cairos
 |first3    = L. M.
 |date      = 2003
 |title     = New insights to the photometric structure of Blue Compact Dwarf Galaxies from deep Near-Infrared Studies
 |url       = http://estallidos.iac.es/estallidos/workshops/workshopI/charlas/KNoeske.pdf
 |archive-url = https://web.archive.org/web/20110815201613/http://estallidos.iac.es/estallidos/workshops/workshopI/charlas/KNoeske.pdf

 |archive-date = 2011-08-15
 |publisher = [[Göttingen Observatory]]
}}</ref><ref>
{{cite journal
 |last1=Meurer |first1=G. R.
 |last2=Mackie |first2=G.
 |last3=Carignan |first3=C.
 |date=1994
 |title=Optical observations of NGC 2915: A nearby blue compact dwarf galaxy
 |journal=[[The Astronomical Journal]]
 |volume=107 |issue=6 |pages=2021–2035
 |bibcode=1994AJ....107.2021M
 |doi=10.1086/117013
}}</ref>

==Ultra-faint dwarf galaxies==
{{anchor|Ultra-faint dwarf galaxies}}

{{See also|Ultra diffuse galaxy}}

[[File:Dark Matter is a No Show in Ghostly Galaxy (gemini1801b).jpg|thumb|A composite color image by the [[Hubble Space Telescope]] of the [[NGC 1052-DF2]]]]
'''Ultra-faint dwarf''' galaxies (UFDs) are a class of [[Galaxy|galaxies]] that contain from a few hundred to one hundred thousand [[star]]s, making them the faintest galaxies in the [[Universe]].<ref>{{Cite journal|last=Simon|first=Joshua D.|date=2019-08-18|title=The Faintest Dwarf Galaxies|url=https://www.annualreviews.org/doi/10.1146/annurev-astro-091918-104453|journal=Annual Review of Astronomy and Astrophysics|language=en|volume=57|issue=1|pages=375–415|doi=10.1146/annurev-astro-091918-104453|arxiv=1901.05465 |bibcode=2019ARA&A..57..375S |s2cid=119384790 |issn=0066-4146}}</ref> UFDs resemble [[globular cluster]]s (GCs) in appearance but have very different properties. Unlike GCs, UFDs contain a significant amount of [[dark matter]] and are more extended.  UFDs were first discovered with the advent of digital sky surveys in 2005, in particular with the [[Sloan Digital Sky Survey]] (SDSS).<ref>{{Cite journal|last1=Willman|first1=Beth|last2=Dalcanton|first2=Julianne J.|last3=Martinez-Delgado|first3=David|last4=West|first4=Andrew A.|last5=Blanton|first5=Michael R.|last6=Hogg|first6=David W.|last7=Barentine|first7=J. C.|last8=Brewington|first8=Howard J.|last9=Harvanek|first9=Michael|last10=Kleinman|first10=S. J.|last11=Krzesinski|first11=Jurek|date=2005-06-20|title=A New Milky Way Dwarf Galaxy in Ursa Major|url=https://iopscience.iop.org/article/10.1086/431760|journal=The Astrophysical Journal|language=en|volume=626|issue=2|pages=L85–L88|doi=10.1086/431760 |arxiv=astro-ph/0503552|bibcode=2005ApJ...626L..85W |s2cid=14851943 |issn=0004-637X}}</ref><ref>{{Cite journal|last1=Willman|first1=Beth|last2=Blanton|first2=Michael R.|last3=West|first3=Andrew A.|last4=Dalcanton|first4=Julianne J.|last5=Hogg|first5=David W.|last6=Schneider|first6=Donald P.|last7=Wherry|first7=Nicholas|last8=Yanny|first8=Brian|last9=Brinkmann|first9=Jon|date=June 2005|title=A New Milky Way Companion: Unusual Globular Cluster or Extreme Dwarf Satellite?|url=https://iopscience.iop.org/article/10.1086/430214|journal=The Astronomical Journal|language=en|volume=129|issue=6|pages=2692–2700|doi=10.1086/430214 |arxiv=astro-ph/0410416|bibcode=2005AJ....129.2692W |s2cid=826898 |issn=0004-6256}}</ref>

UFDs are the most [[dark matter]]-dominated systems known. [[Astronomer]]s believe that UFDs encode valuable information about the early [[Universe]], as all UFDs discovered so far are ancient systems that have likely formed very early on, only a few million years after the [[Big Bang]] and before the epoch of [[reionization]].<ref>{{Cite journal|last1=Bovill|first1=Mia S.|last2=Ricotti|first2=Massimo|title=Pre-Reionization Fossils, Ultra-Faint Dwarfs, and the Missing Galactic Satellite Problem |date=2009-03-10|url=https://iopscience.iop.org/article/10.1088/0004-637X/693/2/1859|journal=The Astrophysical Journal|volume=693|issue=2|pages=1859–1870|doi=10.1088/0004-637X/693/2/1859|arxiv=0806.2340 |bibcode=2009ApJ...693.1859B |s2cid=14543154 |issn=0004-637X}}</ref> Recent theoretical work has hypothesised the existence of a population of young UFDs that form at a much later time than the ancient UFDs.<ref>{{Cite journal|last1=Benitez-Llambay|first1=Alejandro|last2=Fumagalli|first2=Michele|date=2021-11-01|title=The Tail of Late-forming Dwarf Galaxies in ΛCDM|journal=The Astrophysical Journal Letters|volume=921|issue=1|pages=L9|doi=10.3847/2041-8213/ac3006| arxiv=2110.08279|bibcode=2021ApJ...921L...9B |s2cid=239016084 |issn=2041-8205 |doi-access=free }}</ref>  These galaxies have not been observed in our [[Universe]] so far.

==Ultra-compact dwarfs==
[[File:M59-UCD3 M85-HCCI.png|thumb|[[M59-UCD3]] and [[M85-HCC1|M85-HCCI]] are the densest galaxies discovered.]]
'''Ultra-compact dwarf''' galaxies (UCD) are a class of very compact galaxies with very high stellar densities,
discovered<ref name="hilker1999">{{cite journal
   |author1=Hilker, M.
   |author2=Infante, L.
   |author3=Vieira, G.
   |author4=Kissler-Patig, M.
   |author5=Richtler, T.
   |title=The central region of the Fornax cluster. II. Spectroscopy and radial velocities of member and background galaxies
   |journal=[[Astronomy and Astrophysics Supplement]]
   |volume=134
   |date=1999
   |pages=75–86
   |doi=10.1051/aas:1999434
   |bibcode=1999A&AS..134...75H
   |arxiv=astro-ph/9807144
|s2cid=17710039
 }}</ref><ref name="drinkwater2000">{{cite journal
   |author1=Drinkwater, M. J.
   |author2=Jones, J. B.
   |author3=Gregg, M. D.
   |author4=Phillipps, S.
   |title=Compact Stellar Systems in the Fornax Cluster: Super-massive Star Clusters or Extremely Compact Dwarf Galaxies?
   |journal=[[Publications of the Astronomical Society of Australia]]
   |volume=17
   |issue=3
 |date=2000
   |pages=227–233
   |doi=10.1071/AS00034
   |bibcode=2000PASA...17..227D
   |arxiv=astro-ph/0002003
|s2cid=13161406
 }}</ref><ref name="smh2003">
{{cite news|last1=Smith|first1=Deborah|title=Star search finds millions masquerading as one|work=[[Sydney Morning Herald]]|date=29 May 2003|issn=0312-6315|page=5}}
</ref> in the 2000s.
They are thought to be on the order of 200 light years across, containing about 100 million stars.<ref>Anglo-Australian Observatory [https://www.aao.gov.au/public/mediarelease/astronomers-discover-dozen-of-mini-galaxies Astronomers discover dozens of mini-galaxies] {{Webarchive|url=https://web.archive.org/web/20180427015808/https://www.aao.gov.au/public/mediarelease/astronomers-discover-dozen-of-mini-galaxies |date=27 April 2018 }} 0100 AEST Friday 2 April 2004.</ref> It is theorised that these are the cores of nucleated dwarf elliptical galaxies that have been stripped of gas and outlying stars by [[Galactic tide|tidal interactions]], travelling through the hearts of rich clusters.<ref name="kazantzidis2003">
{{cite journal
   |arxiv=astro-ph/0307362
   |author1=Stelios Kazantzidis
   |author2=Ben Moore
   |author3=Lucio Mayer
   |title=Galaxies and Overmerging: What Does it Take to Destroy a Satellite Galaxy?
   |date=2004
   |journal=[[ASP Conference Series]]
   |volume=327
   |page=155
   |url=http://aspbooks.org/custom/publications/paper/327-0155.html
   |bibcode=2004ASPC..327..155K
}}
</ref> UCDs have been found in the [[Virgo Cluster]], [[Fornax Cluster]], [[Abell 1689]], and the [[Coma Cluster]], amongst others.<ref>
{{cite journal
   |author1=Mieske
   |author2=Infante
   |author3=Benitez
   |author4=Coe
   |author5=Blakeslee
   |author6=Zekser
   |author7=Ford
   |author8=Broadhurst
   |author9=Illingworth
   |title=Ultra Compact Dwarf galaxies in Abell 1689: a photometric study with the ACS
   |doi=10.1086/423701
   |date=2004
   |journal=[[The Astronomical Journal]]
   |volume=128
   |issue=4
   |pages=1529–1540
   |arxiv=astro-ph/0406613
   |bibcode=2004AJ....128.1529M
   |display-authors=8
   |last10=Hartig|first10=G. F.
   |last11=Clampin|first11=M.
   |last12=Ardila|first12=D. R.
   |last13=Bartko|first13=F.
   |last14=Bouwens|first14=R. J.
   |last15=Brown|first15=R. A.
   |last16=Burrows|first16=C. J.
   |last17=Cheng|first17=E. S.
   |last18=Cross|first18=N. J. G.
   |last19=Feldman|first19=P. D.
   |last20=Franx|first20=M.
   |last21=Golimowski|first21=D. A.
   |last22=Goto|first22=T.
   |last23=Gronwall|first23=C.
   |last24=Holden|first24=B.
   |last25=Homeier|first25=N.
   |last26=Kimble|first26=R. A.
   |last27=Krist|first27=J. E.
   |last28=Lesser|first28=M. P.
   |last29=Martel|first29=A. R.
   |last30=Menanteau|first30=F.
|s2cid=15575071
 }}</ref>
In particular, an unprecedentedly large sample of ~ 100 UCDs has been found in the core region of the Virgo cluster by the Next Generation Virgo Cluster Survey team.<ref>{{cite web|url=https://www.eso.org/sci/meetings/2012/surveys2012/Presentations/Day3-Wednesday/Ferrarese.pdf|access-date=2023-08-20|title=The Next Generation Virgo Cluster Survey}}</ref> The first ever relatively robust studies of the global properties of Virgo UCDs suggest that
UCDs have distinct dynamical<ref name="zhang2015">{{cite journal
   |title= The Next Generation Virgo Cluster Survey. VI: The Kinematics of Ultracompact Dwarfs and Globular Clusters in M87
   |journal=[[Astrophysical Journal]]
   |date=March 2015
   |last1=Zhang|first1=Hong-Xin|display-authors=etal|doi=10.1088/0004-637X/802/1/30
   |arxiv=1501.03167
   |bibcode=2015ApJ...802...30Z
   |volume=802
   |issue=1
 |page=30
|s2cid=73517961
 }}</ref>
and structural<ref name="liu2015">
{{cite journal
   |title=The Next Generation Virgo Cluster Survey. X: Properties of Ultracompact Dwarfs in The M87, M49 and M60 Regions
   |journal=[[Astrophysical Journal]]
   |date=November 2015
   |last1=Liu|first1=Chengze|display-authors=etal|doi=10.1088/0004-637X/812/1/34
   |arxiv=1508.07334
   |bibcode=2015ApJ...812...34L
   |volume=812
   |issue=1
 |page=34
|s2cid=35610312
 }}</ref> properties from normal globular clusters. An extreme  example of UCD is [[M60-UCD1]], about 54 million light years away, which contains approximately 200 million solar masses within a 160 light year radius; the stars in its central region are packed 25 times more densely than stars in Earth's region in the Milky Way.<ref>
{{cite journal
   |title=The Densest Galaxy
   |journal=[[Astrophysical Journal Letters]]
   |date=August 2013
   |volume=775
   |issue=1
   |pages=L6
   |doi=10.1088/2041-8205/775/1/L6
   |last1=Strader|first1=Jay
   |display-authors=4
   |last2=Seth|first2=Anil C.
   |last3=Forbes|first3=Duncan A.
   |last4=Fabbiano |first4=Giuseppina
   |last5=Romanowsky|first5=Aaron J.
   |last6=Brodie|first6=Jean P.
   |last7=Conroy |first7=Charlie
   |last8=Caldwell|first8=Nelson
   |last9=Pota |first9=Vincenzo
   |last10=Usher|first10=Christopher
   |last11=Arnold|first11=Jacob A.
   |arxiv = 1307.7707
   |bibcode = 2013ApJ...775L...6S
|s2cid=52207639
 }}
</ref><ref>
{{cite web|title=Evidence for densest galaxy in nearby universe|url=http://phys.org/news/2013-09-evidence-densest-galaxy-nearby-universe.html|publisher=Phys.org (Omicron Technology Ltd)|access-date=25 September 2013|date=24 September 2013|quote=What makes M60-UCD1 so remarkable is that about half of this mass is found within a radius of only about 80 light years. The density of stars is about 15,000 times greater—meaning the stars are about 25 times closer to each other—than in Earth's region of the [[Milky Way]] galaxy.
}}
</ref>
[[M59-UCD3]] is approximately the same size as M60-UCD1 with a [[Effective radius|half-light radius]], r<sub>h</sub>, of approximately 20 [[parsecs]] but is 40% more luminous with an [[absolute visual magnitude]] of approximately −14.6.  This makes M59-UCD3 the second densest known galaxy.<ref name=m59-ucd3>{{cite journal
   |last1=Sandoval|first1=Michael A.
   |last2=Vo|first2=Richard P.
   |last3=Romanowsky|first3=Aaron J.
   |last4=Strader|first4=Jay
   |last5=Choi|first5=Jieun
   |last6=Jennings|first6=Zachary G.
   |last7=Conroy|first7=Charlie
   |last8=Brodie|first8=Jean P.
   |last9=Foster|first9=Caroline
   |last10=Villaume|first10=Alexa
   |last11=Norris|first11=Mark A.
   |last12=Janz|first12=Joachim
   |last13=Forbes|first13=Duncan A.
   |title=Hiding in Plain Sight: Record-breaking Compact Stellar Systems in the Sloan Digital Sky Survey
   |journal=[[The Astrophysical Journal]]
   |date=23 July 2015
   |volume=808
   |issue=1
   |pages=L32
   |doi=10.1088/2041-8205/808/1/L32
   |arxiv=1506.08828
   |bibcode=2015ApJ...808L..32S
|s2cid=55254708
 }}</ref>
Based on stellar orbital velocities, two UCD in the Virgo Cluster are claimed to have [[supermassive black holes]] weighing 13% and 18% of the galaxies' masses.<ref name="ahn2017">{{cite journal
   |author1=Ahn, C. P.
   |author2=Seth, A. C.
   |author3=den Brok, M.
   |author4=Strader, J.
   |author5=Baumgardt, H.
   |author6=van den Bosch, R.
   |author7=Chilingarian, I.
   |author8=Frank, M.
   |author9=Hilker, M.
   |author10=McDermid, R.
   |author11=Mieske, S.
   |author12=Romanowsky, A. J.
   |author13=Spitler, L.
   |author14=Brodie, J.
   |author15=Neumayer, N.
   |author16=Walsh, J. L.
   |title=Detection of Supermassive Black Holes in Two Virgo Ultracompact Dwarf Galaxies
   |journal=[[Astrophysical Journal]]
   |volume=839
   |issue=2
 |date=2017
   |page=72
   |doi=10.3847/1538-4357/aa6972
   |bibcode=2017ApJ...839...72A
   |arxiv=1703.09221
|s2cid=55131811
 |doi-access=free
 }}</ref>

==Partial list==
{{div col|colwidth=40 em}}
* [[Aquarius Dwarf]]
* [[Canis Major Dwarf Galaxy]]
* [[Carina Dwarf]]
* [[Crater 2 dwarf]]
* [[Draco Dwarf]]
* [[Eridanus II]]
* [[Fornax Dwarf]]
* [[Henize 2-10]]
* [[I Zwicky 18]]
* [[IC 10]]
* [[Large Magellanic Cloud]]
* [[Leo I (dwarf galaxy)|Leo I]]
* [[Leo II (dwarf galaxy)|Leo II]]
* [[NGC 1569]]
* [[NGC 1705]]
* [[NGC 2915]]
* [[NGC 3353]]
* [[Pegasus Dwarf Irregular Galaxy]]
* [[PHL 293B]]
* [[Phoenix Dwarf]]
* [[Sagittarius Dwarf Spheroidal Galaxy]]
* [[Sagittarius Dwarf Irregular Galaxy]]
* [[Sculptor Dwarf Galaxy]]
* [[Sculptor Dwarf Irregular Galaxy]]
* [[Sextans A]]
* [[Sextans Dwarf Spheroidal]]
* [[Small Magellanic Cloud]]
* [[Tucana Dwarf]]
* [[Ursa Major I Dwarf]]
* [[Ursa Major II Dwarf]]
* [[Ursa Minor Dwarf]]
* [[Willman 1]]
{{div col end}}
[[File:A stubborn dwarf galaxy.jpg|thumb|[[LEDA 677373]] is located about 14 million light-years away.<ref>{{cite web|title=A stubborn dwarf galaxy|url=http://www.spacetelescope.org/images/potw1627a/|access-date=6 July 2016}}</ref>]]
[[File:Dwarf galaxy DDO 68.jpg|thumb|Dwarf galaxy [[DDO 68]].<ref>{{cite web|title=A galaxy of deception|url=http://www.spacetelescope.org/news/heic1421/|access-date=29 September 2014}}</ref>]]

==Gallery==
<gallery>
Hubble’s Legacy - Flickr - europeanspaceagency.jpg|Dwarf galaxy [[UGC 685]] taken by Hubble.<ref>{{cite web |title=Hubble's Legacy |url=https://www.spacetelescope.org/images/potw1935a/ |website=www.spacetelescope.org |access-date=2 September 2019 |language=en}}</ref>
</gallery>

==See also==
* [[Blueberry galaxy]] -  Small and very active galaxies.
* {{annotated link|Galaxy morphological classification}}
* {{annotated link|List of nearest galaxies}}
* {{annotated link|Pea galaxy}}

==References==
{{Reflist|2}}

==External links==
{{Commons category|Dwarf galaxies}}
* [http://www.astro.uu.se/~ns/mwsat.html Milky Way Satellite Galaxies] {{Webarchive|url=https://web.archive.org/web/20140219170336/http://www.astro.uu.se/~ns/mwsat.html |date=19 February 2014 }}
* [http://sciencenow.sciencemag.org/cgi/content/full/2007/109/1 ''Science'' article on "hobbit galaxies"] {{Webarchive|url=https://web.archive.org/web/20090328130213/http://sciencenow.sciencemag.org/cgi/content/full/2007/109/1 |date=28 March 2009 }}
* [http://www.space.com/scienceastronomy/070115_mm_hobbit_galaxies.html SPACE.com article on "hobbit galaxies"]

{{Galaxy}}
{{stellar system}}
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[[Category:Dwarf galaxies| ]]
[[Category:Galaxy morphological types]]