The Triangulum Galaxy is also called M33 for being the 33rd object in Charles Messier’s sky catalog. It is located about 2.9 million light-years from Earth in the constellation Triangulum. It is a member of our Local Group, the small cluster of galaxies that includes our Milky Way Galaxy and the Andromeda Galaxy (M31). Despite sharing our Milky Way’s spiral shape, M33 has only about one-tenth the mass. M33’s visible disk is about 50,000 light-years across, half the diameter of our galaxy.
Swift’s Ultraviolet/Optical Telescope (UVOT) took the images through three separate ultraviolet filters from December 23, 2007 to January 4, 2008. The mosaic showcases UVOT’s high spatial resolution. Individual star clusters and star-forming gas clouds are clearly resolved, even in the crowded nucleus of the galaxy. The image also includes Milky Way foreground stars and much more distant galaxies shining through M33.
M33 – click for 1440× 900 image
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