Microquasar GRO J1655-40

GRO J1655-40 (in blue) is the second so-called 'microquasar' discovered in our Galaxy. Microquasars are black holes of about the same mass as a star. They behave as scaled-down versions of much more massive black holes that are at the cores of extremely active galaxies, called quasars. Their masses can range from 3.5 to approximately 15 times the mass of our Sun.