On the edge of a hungry black hole

Gas and dust equal to the mass of two Earths are being gobbled up every hour by a hungry black hole in a distant galaxy, according to a space telescope probing the Universe in X-rays that has peered closer to a black hole than ever before.

The European Space Agency’s orbiting XMM-Newton observatory studied the black hole in the core of an active galaxy known only as 1H0707-495. This particular galaxy is described as Seyfert 1 galaxy, which typically have bright centres emitting a broad range of hydrogen emission but narrow emission lines of heavier elements such as iron. Four out of five Seyfert galaxies are barred spirals. The bars funnel large amounts of gas into the core, which then feeds into a spiralling disc around the supermassive black hole located in the centre of the galaxy.

As the gas spins around the black hole, it heats up, producing X-rays that then illuminate clumps of matter in the disc. To get a better grasp of the size and distribution of material in this disc, astronomers used XMM-Newton to search for X-rays emitted by iron atoms. They chose iron because it has a distinctive signature that is affected by the spin of the black hole, the velocity at which the iron atoms are orbiting around the black hole, and the energy required to escape the black hole’s gravity. As such, they can tell us a lot about the characteristics of the black hole.