One of the most exotic binary systems we know of is GRO J1655-40. It's some 11,000 light years away, and is made up of a sunlike star and a black hole. The black hole's strong gravity pulls matter away from the other star. But matter doesn't just topple into the black hole. It's pulled into what's called an accretion disk
which orbits the black hole at high velocity. Here is an artist's impression of the system
. At seven solar masses, the black hole would have formed when a massive star used up its fuel, exploded as a supernova and the remnant collapsed into a black hole.