English: The galaxy known as M60-UCD1 (bright white circle near bottom edge, just to the left of center) is located near a massive elliptical galaxy NGC 4649, also called M60, about 54 million light-years from Earth. This image shows M60 and the region around it. Packed with an extraordinary number of stars, M60-UCD1 is an "ultra-compact dwarf galaxy." It is one of the most massive galaxies of its kind, weighing 200 million times more than our Sun, based on observations with the Keck 10-meter telescope in Hawaii. Remarkably, about half of this mass is found within a radius of only about 80 light-years. This would make the density of stars about 15,000 times greater than found in Earth's neighborhood in the Milky Way, meaning that the stars are about 25 times closer.