It is believed that the black hole at the center of our own Milky Way Galaxy, Sagittarius A, is 4 million solar masses. This is the the most massive object in our galaxy. Even so, it is dwarfed in comparison with the black hole located at the center of NGC 4889, a galaxy 308 million light-years away at the center of the Coma Cluster. This elliptical galaxy is one of the brightest and largest galaxies in the Coma Cluster, and even though it doesn’t display much activity, it contains a black hole with a mass 21 billion times that of our Sun.
In a galaxy far, far away (that is to say, about 12.8 billion light-years away) a supermassive black hole has been discovered that is estimated to weigh as much as 12 billion suns and is 420 trillion times brighter than the sun. But it isn’t the weight and size that is baffling scientists–it’s how young it is.