British astronomers discovered five “supermassive” massive black holes, which have previously been hidden under layers of dust and gas. Scientists aren’t ruling out the existence of millions of giant black holes in the universe still hidden from view.

The findings by British astronomers from Durham University have been presented at the Royal Astronomical Society’s National Astronomy Meeting, at Venue Cymru, in Llandudno, Wales.

The five black holes were noticed by NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) orbiting observatory, which can pick up extremely high-energy X-rays from faraway distances and identify black holes that are light years away. Such detailed observations were not possible before the launch of the new observatory in 2012. It is capable of detecting much higher energy X-rays, scientists say.