Tucana Dwarf

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Tucana Dwarf
Tucana Dwarf Hubble WikiSky.jpg
Tucana Dwarf by HST
Observation data (J2000 epoch)
Right ascension22h 41m 49.0s[1]
Declination−64° 25′ 12″[1]
Redshift130 ± ? km/s[1]
Distance3.2 Mly
Apparent magnitude (V)15.7[1]
Apparent size (V)2′.9 × 1′.2[1]
Other designations
PGC 69519[1]
See also: Galaxy, List of galaxies

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 is a dwarf spheroidal galaxy of type dE5.[2] It contains only old stars, formed in a single star formation era around the time the Milky Way's globular clusters formed.[3] It is not experiencing any current star formation, unlike other isolated dwarf galaxies.[4]

The Tucana Dwarf does not contain very much neutral hydrogen gas.[5] It has a metallicity of -1.8, a significantly low number. There is no significant spread in metallicity throughout the galaxy.[3] There does not seem to be any substructure to the stellar distribution in the galaxy.[3]


The Tucana Dwarf is located in the constellation Tucana. It is about 870 kiloparsecs (2,800 kly) away,[6] 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,[2] as well as the role of environment in determining how dwarf galaxies evolve. It is isolated from other galaxies,[2] and located near the edge of the Local Group,[3] around 1,100 kiloparsecs (3,600 kly) from the barycentre of the Local Group—the second most remote of all member galaxies after the Sagittarius Dwarf Irregular Galaxy.[6]

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.[7] It is therefore likely to have evolved in isolation for most of its history.[6]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  2. 2.0 2.1 2.2 Lavery, Russell J.; Mighell, Kenneth J. (January 1992). "A new member of the Local Group - The Tucana dwarf galaxy". The Astronomical Journal 103 (1): 81–84. Bibcode 1992AJ....103...81L. doi:10.1086/116042.
  3. 3.0 3.1 3.2 3.3 Saviane, I.; Held, E. V.; Piotto, G. (November 1996). "CCD photometry of the Tucana dwarf galaxy.". Astronomy and Astrophysics 315: 40–51. arXiv:astro-ph/9601165. Bibcode 1996A&A...315...40S.
  4. van den Bergh, Sidney (June 1994). "The evolutionary history of low-luminosity local group dwarf galaxies". The Astrophysical Journal 428: 617–619. Bibcode 1994ApJ...428..617V. doi:10.1086/174270.
  5. Oosterloo, T.; Da Costa, G. S.; Staveley-Smith, L. (November 1996). "HI Observations of the Tucana Dwarf Elliptical Galaxy". The Astronomical Journal 112 (5): 1969–1974. Bibcode 1996AJ....112.1969O. doi:10.1086/118155.
  6. 6.0 6.1 6.2 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
  7. Fraternali, F.; Tolstoy, E.; Irwin, M. J.; Cole, A. A. (May 2009). "Life at the periphery of the Local Group: the kinematics of the Tucana dwarf galaxy". Astronomy and Astrophysics. arXiv:0903.4635. Bibcode 2009A&A...499..121F. doi:10.1051/0004-6361/200810830.

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