By Ron Cowen
Jets of high-speed particles riddle the celestial canvas. They are generated by dramatically different objects: nascent stars still in the process of coalescing, massive stars that have collapsed to form the smallest of black holes, and supermassive black holes weighing as much as a billion suns. Astronomers have long dreamed of having one theory that could explain the origin and evolution of all these jets. New observations are bringing that vision one step closer to reality. For the first time, scientists have traced the slowing and dimming of X-ray–emitting jets from a small black hole. Monitoring the jets with the orbiting Chandra X-ray Observatory over the past 2 years, researchers have viewed the jets as they traveled at half the speed of light, slowed down, and faded.
The jets emanate from the region surrounding a small black hole within the Milky Way that is about 10 times as massive as the sun. Compared with supermassive black holes, which can weigh as much as a billion suns and last millions of years, small black holes have a limited fuel supply and their jets have a much shorter lifetime.