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Discovery of a Large and Diffuse Dwarf Galaxy

28 Jan 2016, 10:00 UTC
Discovery of a Large and Diffuse Dwarf Galaxy
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Torrealba et al. (2016) present the discovery of a dwarf galaxy identified as Crater 2. It is a satellite galaxy of the Milky Way that is estimated to lie ~380,000 light years from the Sun. The half-light radius of Crater 2 is ~3500 light years in size. A dwarf galaxy does not have a clear boundary since the density of stars gradually decreases towards the outer regions. For this reason, the size of a dwarf galaxy is measured by its half-light radius, which is basically the distance from the center of the dwarf galaxy, whereby within this radius, half the total brightness of the galaxy is emitted. In fact, the sizes of other types of stellar systems such as globular clusters are also denoted by the half-light radius.Crater 2 has an extremely low surface brightness of only ~31 mag/arcsecĀ². The discovery of Crater 2 indicates that a substantial number of extremely low surface brightness dwarf galaxies have yet to be detected. Crater 2 is a remarkable dwarf galaxy because it is the largest known ultra-faint satellite galaxy of the Milky Way and the fourth largest satellite galaxy, surpassed only by the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC) ...

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