Ten monster black holes hanging around in the distant galaxies have been discovered by NASA’s powerful space telescope.

This discovery is the first major for the X-ray space observatory, said scientists. The “serendipitously” discovery, as scientists call it, happened when astronomers looked into photos from NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), s space-based X-ray telescope specially designed to look for black holes that are billion times bigger than the sun.

Professor David Alexander, of the University of Durham’s physics department told Space.com, "We were looking at known targets and spotted the black holes in the background of the images."

The astronomers then affirmed what they saw with NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton Satellite’s observations. The XMM-Newton Satellite is also capable of looking at low-energy light.

The newly found 10 black holes are just the start of more anticipated discoveries. The scientists are hoping to understand more of the populations as every monster black holes are recorded.

According to NASA, the discovery of monster black holes were important pieces of a puzzle first unveiled in 1962. Astronomers discovered a glow in the background of the universe but were clueless as to where it came from.

Scientists now know that the glow or the “cosmic X-ray background” comes from very distant monster black holes, which are as big as the sun’s size multiplied by 17 billion. However, where these monster black holes originated from are still unknown.

Daniel Stern, project scientist for NuSTAR and co-author of the study wrote in the Aug.20 issue of the Astrophysical Journal, "Our early results show that the more distant supermassive black holes are encased in bigger galaxies. This is to be expected. Back when the universe was younger, there was a lot more action with bigger galaxies colliding, merging and growing."

Though, NuSTAR can detect monster black holes, measurements are from Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE).