Black holes are as massive as they are mysterious. It is believed that in the Milky Way there are between ten and one billion of these cosmic objects, and although they are tremendously difficult to detect and quantify, a group of astronomers has managed to create a visual map of more than 20,000 of them in the sky.
At first glance, the image published by researchers at the University of Hamburg in Germany may look like a starry sky, but in reality each white dot represents an active supermassive black hole devouring a star millions of light years away.
A map that took years to build
Black holes are not visible with traditional observing instruments, however, can be detected from Earth when they devour a star or pass near a cloud of interstellar matter and consequently interact with its accretion disc disk composed of gas and dust.
As black holes attract stellar material and tear it apart, they emit enormous amounts of X-rays. These high-energy signals can be detected by LOw Frequency ARray (PROMISES), a network of radio telescopes distributed over 52 stations located in different parts of Europe.
Precisely, the group of astronomers led by Huub Röttgerin from the Leiden Observatory used LOFAR to map four percent of the northern hemisphere and thus detect some 25,000 supermassive black holes, resulting in the “most detailed sky map in the field of so-called low radio frequencies.”
The astronomers, who have published their research in Astronomy & Astrophysics, point out that the ionosphere negatively interfered in the mission of mapping part of the sky in search of black holes through LOFAR. To overcome that problem, researchers turned to supercomputers with new algorithms to correct for interference.
The team plans to continue mapping the entire Northern Hemisphere. In addition to supermassive black holes, the map will also help to gain insight into the large-scale structure of the universe.
“After many years of software development, it is wonderful to see that this has really worked,” said one of the project members, the Leiden Observatory astronomer, Huub Röttgering.
Via | Science Alert
More information | Leiden University