三角座星系
Unlike the Milky Way and Andromeda galaxies, the Triangulum Galaxy does not appear to have a supermassive black hole at its center. This may be because the mass of a galaxy's central supermassive black hole correlates with the size of the galaxy's central bulge, and unlike the Milky Way and Andromeda, the Triangulum Galaxy is a pure disk galaxy with no bulge.