Dwarf galaxy

Dwarf galaxy
UGC 9128 is a dwarf irregular galaxy, it probably contains only around one hundred million stars.

A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars. The Large Magellanic Cloud, containing over 30 billion stars, is sometimes classified as a dwarf galaxy while others consider it a full-fledged galaxy orbiting the Milky Way galaxy.


Formation of dwarf galaxies

Current theory states that most galaxies, including dwarf galaxies, form in association with dark matter or out of gas containing metals. However, NASA's Galaxy Evolution Explorer space probe identified new dwarf galaxies forming out of gases lacking metals. These galaxies were located in the Leo Ring, a cloud of hydrogen and helium around two massive galaxies in the constellation Leo.[1]

Local dwarfs

Phoenix dwarf galaxy is a dwarf irregular galaxy, features younger stars in its inner regions and older ones at its outskirts[2].

There are many dwarf galaxies in the Local Group: these small galaxies frequently orbit around larger galaxies, such as the Milky Way, the Andromeda Galaxy and the Triangulum Galaxy. A 2007 paper[3] has suggested that many dwarf galaxies were created by tidal forces during the early evolution of the Milky Way and Andromeda. Tidal dwarf galaxies are produced when galaxies collide and their gravitational masses interact. Streams of galactic material are pulled out away from the parent galaxies and the halos of dark matter that surround them.[4]

The Milky Way has 14 known dwarf galaxies orbiting it, and recent observations[5] 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 in its center, which was at some time absorbed by the Milky Way.

Dwarf galaxies

Dwarf galaxies come in many different morphologies:

Hobbit galaxies

The recently coined term, hobbit galaxy has been used to describe galaxies smaller and dimmer than dwarf galaxies.[6][7]

Ultra Compact Dwarfs

Ultra Compact Dwarf galaxies (UCD) are a recently discovered class of very compact galaxies with very high stellar population counts. They are thought to be on the order of 200 light years across, with a hundred million stars.[8] It is theorized that these are the cores of nucleated dwarf elliptical galaxies, that have been stripped of gas and outlying stars by tidal interactions, travelling through the hearts of rich clusters.[9] UCDs have been found in the Virgo Cluster, Fornax Cluster, Abell 1689, Coma Cluster, amongst other clusters.[10]

Partial list of dwarf galaxies

See also


  1. ^ UPI, "New Recipe For Dwarf Galaxies: Start With Leftover Gas", Science Daily, 19 Feb 2009 [1]
  2. ^ "Hubble Sizes up a Dwarf Galaxy". Picture of the Week. ESA/Hubble. http://spacetelescope.org/images/potw1143a/. Retrieved 25 October 2011. 
  3. ^ Metz, M.; Kroupa (2007). "Dwarf-spheroidal satellites: are they of tidal origin?". Monthly Notices of the Royal Astronomical Society 376: 387–392. arXiv:astro-ph/0701289. Bibcode 2007MNRAS.376..387M. doi:10.1111/j.1365-2966.2007.11438.x. 
  4. ^ New Recipe for Dwarf Galaxies: Start with Leftover Gas Newswise, Retrieved on February 20, 2009.
  5. ^ Noyola, E. and Gebhardt, K. and Bergmann, M. (apr 2008). "Gemini and Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in ω Centauri". The Astrophysical Journal 676 (2): 1008–1015. arXiv:0801.2782. Bibcode 2008ApJ...676.1008N. doi:10.1086/529002. 
  6. ^ SPACE.com - New 'Hobbit' Galaxies Discovered Around Milky Way
  7. ^ http://sciencenow.sciencemag.org/cgi/content/full/2007/109/1
  8. ^ Anglo-Australian Observatory Astronomers discover dozens of mini-galaxies 0100 AEST Friday 2 April 2004
  9. ^ Stelios Kazantzidis; Ben Moore; Lucio Mayer (2003). "Galaxies and Overmerging: What Does it Take to Destroy a Satellite Galaxy?". arXiv:astro-ph/0307362 [astro-ph]. 
  10. ^ Mieske; Infante; Benitez; Coe; Blakeslee; Zekser; Ford; Broadhurst et al. (2004). "Ultra Compact Dwarf galaxies in Abell 1689: a photometric study with the ACS". The Astronomical Journal 128 (4): 1529–1540. arXiv:astro-ph/0406613. Bibcode 2004AJ....128.1529M. doi:10.1086/423701. 

External links

Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Dwarf galaxy problem — The dwarf galaxy problem is one that arises from numerical cosmological simulations that predict the evolution of the distribution of matter in the universe. Dark matter seems to cluster hierarchically and in ever increasing number counts for… …   Wikipedia

  • dwarf galaxy — noun Any galaxy, considerably smaller than the Milky Way, that has only several billions of stars. See Also: giant galaxy …   Wiktionary

  • Canis Major Dwarf Galaxy — Infobox Galaxy name = Canis Major Dwarf epoch = J2000 type = Irr ra = RA|07|12|35.0cite web title=NASA/IPAC Extragalactic Database work=Results for Canis Major Dwarf url=http://nedwww.ipac.caltech.edu/cgi bin/nph… …   Wikipedia

  • Coma Berenices (dwarf galaxy) — Coma Berenices Dwarf Galaxy[1] Observation data (J2000 epoch) Constellation Coma Berenices Right ascension 12h 26m 59s …   Wikipedia

  • Leo I (dwarf galaxy) — Leo I Observation data (J2000 epoch) Constellation Leo Right ascension 10h 08m 27.4s[1] …   Wikipedia

  • Sculptor Dwarf Galaxy — Infobox Galaxy name =Sculptor Dwarf Elliptical Galaxy epoch = J2000 ra = RA|01|00|09.3cite web title=NASA/IPAC Extragalactic Database work=Results for PGC 3589 url=http://nedwww.ipac.caltech.edu/ accessdate=2006 12 03] dec = DEC| 33|42|33… …   Wikipedia

  • Boötes Dwarf Galaxy — Infobox Galaxy name = Boötes Dwarf Galaxy epoch = J2000 type = dSphcite journal author=Belokurov, V.; Zucker, D. B.; Evans, N. W.; Wilkinson, M. I.; Irwin, M. J.; Hodgkin, S.; Bramich, D. M.; Irwin, J. M.; Gilmore, G.; Willman, B.; Vidrih, S.;… …   Wikipedia

  • Leo II (dwarf galaxy) — Leo II Observation data (J2000 epoch) Constellation Leo Right ascension 11h 13m 29.2s [1] …   Wikipedia

  • Blue compact dwarf galaxy — In astronomy, a blue compact dwarf galaxy (BCD galaxy) is a small galaxy which contains large clusters of young, hot, massive stars. These stars cause the galaxy to appear blue in color. [http://www.daviddarling.info/encyclopedia/B/blue compact… …   Wikipedia

  • Sculptor (dwarf galaxy) — There is more than one dwarf galaxy in Sculptor* Sculptor Dwarf Galaxy * Sculptor Dwarf Irregular Galaxy (SDIG) …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”