Dense Dwarfs

Ultra-compact dwarf galaxies are a class of very compact galaxies with very high stellar densities. An extreme example of a UCD is M60-UCD1 which contains approximately 200 million solar masses within a 160 light-year radius. The stars in its cental region are about 25 times closer together than the stars in our part of the Milky Way. M59-UCD3 is approximately the same size as M60-UCD1 with a half-light radius, but it’s 40% more luminous. This makes M59-UCD3 the densest known galaxy.

Image Credit: NASA

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