According to the scientists, the two supermassive black holes have enormous gravity and are located at the center of a galaxy about 5 billion light years away from Earth (one light year is equivalent to 10 trillion kilometers, the distance light travels in one year). Data from the Apache Mountain Observatory in New Mexico gives us the best evidence yet of how long the two black holes have been orbiting each other, says astronomer Todd Polson of the National Optical Observatory in Tucson, Arizona.