Monster black holes discovered
Five monster black holes that were previously hidden by dust and gas have been uncovered by astronomers.
The British-led discovery suggests there may be millions more "supermassive" black holes in the universe than were previously thought.
Supermassive black holes are powerful cosmic "drains" sucking material into a point of infinite density formed from the compressed mass of hundreds of thousands to billions of suns.
High energy X-rays emitted from around the newly identified black holes revealed their presence at the centre of five galaxies.
They were detected by the American space agency Nasa's Nuclear Spectroscopic Telescope Array (NuSTAR) orbiting observatory which was launched in 2012.
The space telescope is designed to pick up extremely high energy X-rays from distant objects.
Lead scientist George Lansbury, from the Centre for Extragalactic Astronomy at the University of Durham, said: "For a long time we have known about supermassive black holes that are not obscured by dust and gas, but we suspected that many more were hidden from our view.
"Thanks to NuSTAR for the first time we have been able to clearly see these hidden monsters that are predicted to be there, but have previously been elusive because of their 'buried' state.
"Although we have only detected five of these hidden supermassive black holes, when we extrapolate our results across the whole universe then the predicted numbers are huge and in agreement with what we would expect to see."
The scientists presented their findings at the Royal Astronomical Society's National Astronomy Meeting, in Llandudno, Wales.
Dr Daniel Stern, NuSTAR project scientist at the American space agency Nasa's Jet Propulsion Laboratory in Pasadena, US, said: "High-energy X-rays are more penetrating than low-energy X-rays, so we can see deeper into the gas burying the black holes. NuSTAR allows us to see how big the hidden monsters are and is helping us learn why only some black holes appear obscured."
The research, funded by the Science and Technology Facilities Council (STFC), has been accepted for publication in The Astrophysical Journal.