Astronomers from the UK and the US have observed clumps of gas complete an orbit around a black hole for the first time. The team calculated that the gas is travelling at a speed of 33 000 kilometres per second -- about one-tenth of the speed of light -- and that the black hole must be at least 300 000 times the mass of our Sun. The work was presented at the American Astronomical Society (AAS) meeting in San Diego yesterday.
Supermassive black holes contain billions of solar masses compressed into a volume the size of our solar system. Their gravity of a black hole is so strong that nothing, not even light, can escape. Black holes attract large amounts of gas and dust, which form an accretion disk around the hole before succumbing to the force of gravity. The friction encountered by the material in the accretion disk heats it up and makes it emit X-rays.
Jane Turner and Ian George from NASA and the University of Maryland Baltimore County (UMBC), James Reeves from NASA and Lance Miller from Oxford University studied the Markarian 766 galaxy, which contains a black hole that is several million times as massive as the Sun, using the EPIC cameras onboard the European Space Agency’s XMM-Newton satellite.
Turner and colleagues observed the flares that erupt on the black hole’s accretion disk for periods as long as 27 hours. They calculated the speed of the flares and the length of time they took to orbit the black hole by measuring their Doppler shift. “With a measured velocity and orbital period [of the flares], we could determine the black hole mass using relatively simple Newtonian physics,” said Miller.
“If the black hole in question were placed in our solar system, it would be as wide as Mercury’s orbit, with the three clumps of matter detected orbiting as far out as Jupiter,” he added. “They orbit the black hole in a lightning-quick 27 hours, compared to the 12 years it takes Jupiter to orbit the Sun.”
