Tags: Galaxy.
M60-UCD1 is an ultracompact dwarf galaxy and possibly the densest known galaxy. It is 54 million light years from Earth close to Messier 60 (NGC 4649). Half of its mass is in the central sphere 160 light years in diameter. Its mass is 200 million solar masses. Metallicity is similar to the sun. There is a bright X-ray source in the centre possibly a black hole.
