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| The '''Tucana Dwarf Galaxy''' is a [[dwarf galaxy]] in the [[constellation]] [[Tucana]]. It was discovered in 1990 by R.J. Lavery of [[Mount Stromlo Observatory]]. It is composed of very old stars and is very isolated from other galaxies. Its location on the opposite side of the Milky Way from other [[Local Group]] galaxies makes it an important object for study. | | The '''Tucana Dwarf Galaxy''' is a [[dwarf galaxy]] in the [[constellation]] [[Tucana]]. It was discovered in 1990 by R.J. Lavery of [[Mount Stromlo Observatory]]. It is composed of very old stars and is very isolated from other galaxies. Its location on the opposite side of the Milky Way from other [[Local Group]] galaxies makes it an important object for study. |
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| ==Properties==
| | [[Merajul Islam]] |
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| The Tucana Dwarf is a [[dwarf spheroidal galaxy]] of [[Galaxy morphological classification|type dE5]].<ref name="LaveryMighell1992"/> It contains only old stars, formed in a single [[star formation]] era around the time the Milky Way's [[globular cluster]]s formed.<ref name="SavianeEtAl1996"/> It is not experiencing any current star formation, unlike other isolated dwarf galaxies.<ref name="vandenbergh1994"/>
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| The Tucana Dwarf does not contain very much neutral [[hydrogen]] gas.<ref name="OosterlooEtAl1996"/> It has a [[metallicity]] of -1.8, a significantly low number. There is no significant spread in metallicity throughout the galaxy.<ref name="SavianeEtAl1996"/> There does not seem to be any substructure to the stellar distribution in the galaxy.<ref name="SavianeEtAl1996"/>
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| ==Location==
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| The Tucana Dwarf is located in the constellation Tucana. It is about {{convert|870|kpc|kly}} away,<ref name="vandenbergh2000"/> on the opposite side of the [[Milky Way]] galaxy to most of the other [[Local Group]] galaxies and is therefore important for understanding the kinematics and formation history of the Local Group,<ref name="LaveryMighell1992"/> as well as the role of environment in determining how dwarf galaxies evolve. It is isolated from other galaxies,<ref name="LaveryMighell1992"/> and located near the edge of the Local Group,<ref name="SavianeEtAl1996"/> around {{convert|1100|kpc|kly}} from the barycentre of the Local Group—the second most remote of all member galaxies after the [[Sagittarius Dwarf Irregular Galaxy]].<ref name="vandenbergh2000"/>
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| The Tucana Dwarf galaxy is one of only two dwarf spheroidal galaxies in the Local Group not located near the Milky Way or the [[Andromeda Galaxy]].<ref name="FraternaliEtAl2009"/> It is therefore likely to have evolved in isolation for most of its history.<ref name="vandenbergh2000"/>
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| ==References==
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| {{reflist|refs=
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| <ref name="LaveryMighell1992">{{Cite journal
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| | doi = 10.1086/116042
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| | last = Lavery
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| | first = Russell J.
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| |author2=Mighell, Kenneth J.
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| | title = A new member of the Local Group - The Tucana dwarf galaxy
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| | journal = [[The Astronomical Journal]]
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| | volume = 103
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| | issue = 1
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| | pages = 81–84
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| | date = January 1992
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| | bibcode = 1992AJ....103...81L}}</ref>
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| <ref name="FraternaliEtAl2009">{{Cite journal
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| | last1 = Fraternali | first1 = F.
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| | last2 = Tolstoy | first2 = E.
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| | last3 = Irwin | first3 = M. J.
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| | last4 = Cole | first4 = A. A.
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| | title = Life at the periphery of the Local Group: the kinematics of the Tucana dwarf galaxy
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| | journal = [[Astronomy and Astrophysics]]
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| | date = May 2009
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| | volume = 499
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| | issue = 1
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| | pages = 121–128
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| | bibcode = 2009A&A...499..121F|doi = 10.1051/0004-6361/200810830 |arxiv = 0903.4635 | s2cid = 18698184
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| }}</ref>
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| <ref name="OosterlooEtAl1996">{{Cite journal
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| | doi = 10.1086/118155
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| | last1 = Oosterloo | first1 = T.
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| | last2 = Da Costa | first2 = G. S.
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| | last3 = Staveley-Smith | first3 = L.
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| | title = HI Observations of the Tucana Dwarf Elliptical Galaxy
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| | journal = [[The Astronomical Journal]]
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| | volume = 112
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| | issue = 5
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| | pages = 1969–1974
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| | date = November 1996
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| | bibcode = 1996AJ....112.1969O}}</ref>
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| <ref name="SavianeEtAl1996">{{Cite journal
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| | last1 = Saviane | first1 = I.
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| | last2 = Held | first2 = E. V.
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| | last3 = Piotto | first3 = G.
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| | title = CCD photometry of the Tucana dwarf galaxy.
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| | journal = Astronomy and Astrophysics
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| | volume = 315
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| | pages = 40–51
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| | date = November 1996
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| | bibcode = 1996A&A...315...40S|arxiv = astro-ph/9601165 }}</ref>
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| <ref name="vandenbergh1994">{{Cite journal
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| | doi = 10.1086/174270
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| | last = van den Bergh
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| | first = Sidney
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| | title = The evolutionary history of low-luminosity local group dwarf galaxies
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| | journal = [[The Astrophysical Journal]]
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| | volume = 428
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| | pages = 617–619
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| | date = June 1994
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| | bibcode = 1994ApJ...428..617V}}</ref>
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| <ref name="vandenbergh2000">{{Cite journal
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| | last1 = van den Bergh
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| | first1 = Sidney
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| | authorlink1 = Sidney van den Bergh
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| | title = Updated Information on the Local Group
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| | date = April 2000
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| | journal = [[The Publications of the Astronomical Society of the Pacific]]
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| | volume = 112
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| | issue = 770
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| | pages = 529–536
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| | bibcode = 2000PASP..112..529V
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| | doi = 10.1086/316548
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| |arxiv = astro-ph/0001040 | s2cid = 1805423
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| }}</ref>
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| }}
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| ==External links==
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| * [https://web.archive.org/web/20051116070034/http://www.aas.org/publications/baas/v28n2/aas188/abs/S009003.html The Tucana Dwarf Galaxy: HST/WFPC2 Imaging of this Isolated Local Group Dwarf Spheroidal] (AAS)
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| *{{WikiSky|name=The Tucana Dwarf}}
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| {{Sky|22|41|49.0|-|64|25|12|3200000}}
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| {{Tucana}}
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| {{Authority control}}
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| {{DEFAULTSORT:Tucana Dwarf}}
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| [[Category:Dwarf galaxies]]
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| [[Category:Dwarf elliptical galaxies]]
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| [[Category:Local Group]]
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| [[Category:Tucana (constellation)]]
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| [[Category:Principal Galaxies Catalogue objects|69519]]
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| [[Category:Astronomical objects discovered in 1990]]
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