NASA has begun to find hidden supermassive black holes more often, but this is not enough for scientists

It is believed that at the center of almost all galaxies there are supermassive black holes (SMBs), which seriously influence their evolution. This could be confirmed by direct observation; fortunately, SSDs with masses ranging from hundreds of millions to billions of solar masses are like a bull in a china shop: they are difficult to miss. However, the problem is that black holes are clearly visible only if they are facing us. If they are located edge-on, dust and gas reliably hide even the brightest of them.

A cloud of dust around a black hole in infrared, visible and x-ray light (bottom), with a range of strong energies on the right. Image source: NASA

Previous research suggests that dust and gas hide about 15% of all supermassive black holes. The theory suggests that there should be about 50% of such objects. The new work, based on archival data from the IRAS telescope from the 1980s and the NuSTAR (Nuclear Spectroscopic Telescope Array) X-ray telescope launched in 2012, allowed NASA scientists to conclude that 35% of supermassive black holes are hidden behind clouds of dust and gas. This result is better than previous studies, but still falls short of theoretical expectations.

More accurate knowledge of the number of supermassive black holes and their location in the centers of galaxies is necessary to understand the evolution of the latter. Black holes take material from galaxies that could be used to form new stars (without black holes, galaxies would be much larger than we observe). In addition, SMBHs can stop star formation by absorbing large volumes of matter. This results in powerful bursts of energy and particles that push matter out of the galaxies.

Nuclear Spectroscopic Telescope Array Observatory

Since it is impossible to cover the Universe, scientists draw conclusions about the processes in it based on a relatively small sample of objects. Therefore, it is important to know how much of the NSD may be hidden behind the dust clouds in order to make the sampling as accurate as possible. Fortunately, observations in the infrared and high-energy X-rays make it possible to detect black holes even when they face us edge-on, rather than with bright poles with an accretion disk, jets, and light effects. High-energy X-rays and infrared light cause secondary glows in clouds of dust and gas, allowing scientists to detect hidden supermassive black holes. It is thanks to these methods that NASA scientists were able to identify more black holes where other observations were powerless.