NASA has recently discovered a series of black holes that are hardly seen as they are covered by gas or dust. They sometimes remain unnoticed by telescopes. The only way they are detected is if they emit X-rays packed with great energy.

NASA’s Nuclear Spectroscopic Telescope Array discovered such black holes. Recently, it discovered 2 that are placed at the centers of the next galaxies.

Ady Annuar, who presented the two discoveries, said that they are pretty close to the Milky Way. “They’re like monsters hiding under your bed,” added the graduate student.

Astronomers identify this black holes as bright items that contain quasars and blazars. When they are examined with a telescope, they can appear different based on their position and the material that surround them.

The reason why they appear so bright is because they have particles surrounding them that emit radiations and turn them really hot. If some of the black holes appear really bright, some are hidden by dust and gas.

The recently discovered black holes were pretty tough seen by the astronomers. All they actually see is the material surrounding them that is shaped like a donut.

Peter Boorman, a graduate student from University of Southampton, studied a galaxy that is 170 years away. “Just as we can’t see the sun on a cloudy day, we can’t directly see how bright these active galactic nuclei really are because of all of the gas and dust surrounding the central engine,” explained Boorman the black hole phenomenon.

NUSTAR makes it easier to detect black holes as sometimes they are covered by stars.