Astronomers do not always discover new structures in the landscape of the Universe. More often, their job is to better understand and catalog the knowledge we already have.
In a mammoth work and of an international character, several European astronomers have published on Astronomy & Astrophysics a three-dimensional map of the sky, containing more than 25,000 super massive black holes, celestial bodies of mass billions of times greater than that of the Sun. Super-massive black holes are found at the center of galaxies and it is not very clear how they form. Alternatively, there are two other types of black holes in the Universe.
The map, which might be admired at the bottom of the news, seems to contain thousands of stars, but the truth is that each of the white dots you see represents a super massive black hole. The map is the result of many years of work to develop the software and methods necessary for the measurement, as stated by the head of research Francesco De Gasperin, of the University of Hamburg.
There more complicated challenge that the researchers had to go through to shape the map was definitely finding a way to convert radio signals from black holes in images of the sky. In fact, longer radio waves are shielded and / or refracted by the Earth’s atmosphere, specifically the ionosphere, similar to what we have explained here. It is therefore necessary to reconstruct the radio signal to understand where it came from before measuring it. As the researchers say, it’s kind of like observe a world inside a swimming pool.
The map was created with a ‘observation of the sky 256 consecutive hours, while the data is analyzed in real time by various super-computers that corrected the effects of the ionosphere every four seconds. Right now the map covers 4% of the sky visible from the northern hemisphere of our planet, but researchers are working to expand it. Their idea is to add to the map too other structures of the Universe, in addition to super-massive black holes.