Around 300 million super-massive black holes are swallowing up the universe, astronomers have revealed.
The amazing figure was disclosed by US scientists who have been observing with an orbiting Nasa space telescope.
They had believed there was a background “fog” of X-rays from across the universe.
But close-up studies have revealed that the radiation all comes from separate galaxies – each with a huge black hole devouring stars at its centre like a cosmic plughole.
Professor Niel Brandt used Nasa’s Chandra Observatory to study a part of the sky just two-thirds the size of the full moon.
In that tiny region, he matched individual X-ray sources – black holes – with 600 distant galaxies photographed by the Hubble space telescope.
That means that across the sky there must be 300 million of them. They are so dense that light cannnot escape but the radiation gives away their existence as matter swirls into them.
Our own Milky Way home galaxy has a black hole at its centre, equal to the mass of 2.6 million suns but it is considered to be inactive.
The European Southern Observatory image, above right, shows the central 5,500 light-years wide region of the spiral galaxy NGC 1097 which it thought to contain a super-massive black hole.
Professor Brandt, of Pennsylvania State University, told the annual meeting of the American Association for the Advancement of Science in St Louis: “We wanted a census of all the black holes and to measure how black holes have grown over the history of the universe.”

© Paul Sutherland. Unauthorised reproduction forbidden.