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What is a Dwarf Galaxy?
As the name suggests, a dwarf galaxy is a small galaxy made up of a billion stars. It is formed out of gas containing metals or in association with dark matter. But, new theories based on NASA’s Galaxy Evolution Explorer space probe suggest that some dwarf galaxies are also formed out of gases containing no metals. The Large Magellenic Cloud is one of the best examples of a dwarf galaxy
The Canis Major Dwarf Galaxy can be called as a satellite of the Milky Way since it is the closest one to the center of our own galaxy. It is an irregular galaxy, i.e. a galaxy that has no elliptical or spiral shape, and hence it does not come under the Hubble Sequence of regular galaxy classes. Let’s check out some more interesting facts about this dwarf galaxy.
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Facts about the Canis Major Dwarf Galaxy
Type: Irr (Irregular Galaxy)
Constellation: Canis Major
Distance: 25,000 light-years from the Sun, 42,000 ly from the center of the Milky Way
Apparent dimensions: 12° x 12°
Right ascension: 07 hours, 12 minutes and 35.0 seconds
Declination: -27 degrees
History: The Canis Major Dwarf Galaxy was discovered by a team of British, Australian, French, Italian astronomers in November 2003. Using the Two-Micron All Sky Survey (2MASS) technique, the International team of scientists was easily able to detect class M giant stars and galaxies in constellation Canis Major.
Initiated in the late 1990s, the 2MASS survey technique uses automated telescopes that scan the entire sky using infrared wavelengths. Because gas and dust cannot block infrared, it becomes easier for astronomers to detect galaxies hidden in dense concentration of stars, dust and gases.
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Some More Interesting Facts
- The galaxy contains a very high percentage of red giant stars—giant stars with low mass and very low surface temperature. There are roughly one billion stars in this dwarf galaxy.
- It is the closest known galaxy to the Milky Way; the second most closest is the Sagittarius Dwarf Elliptical galaxy.
- Most astronomers are of the opinion that this dwarf galaxy is being pulled apart by Milky Way’s strong gravitational field progressively. The gravitational pull of our galaxy is so high that both Sagittarius Elliptical and Canis Major dwarfs are being absorbed into the Milk Way—a process, however, will complete within a billion years or so.
- Astronomers are of the opinion that the Canis Major dwarf galaxy may have been brought together with different globular clusters, including NGC 2298 and NGC 1851. Astronomers also believe that the galaxy may have been connected with AM2, Dol 25 and other open clusters.
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Image Credit: Observatoire de Strasbourg (France). Credit: N. Martin, R. Ibata, M. Bellazzini, M.J. Irwin, G.F. Lewis, W. Dennen. (http://www.nasaimages.org/luna/servlet/detail/NVA2~4~4~5151~105677:Canis-Major-Dwarf--A-New-Closest-Ga)