The aforementioned image might look like a typical night sky picture, but you are actually looking at something much more spectacular than just a few glittering stars. Each of those white dots is an active supermassive black hole.
Each one of these black holes is devouring substance in the center of a universe millions of light years away, and that’s the way they were located.
This picture, released in 2021, has 25,000 like dots. It is probably the most comprehensive map of black holes at minimal radio frequencies, an achievement that took many years and a Europe-sized radio telescope.
“This is the outcome of several years of work on extremely challenging data,” explained astronomer Francesco de Gasperin of the University of Hamburg in Germany back in February 2021.
“We needed to discover new techniques to transform the radio signals into pictures of the sky.”
When they are simply hanging out not doing a lot, black holes do not give off the detectable radiation, which makes them much tougher to find.
Whenever a black hole is definitely accreting material – spooling it in out of a disc of debris and gas which circles it a lot as water circles a drain – the intensive forces involved produce radiation across several wavelengths that we are able to identify across the vastness of space.
The thing that makes the above mentioned picture so unique is it covers the ultra low radio wavelengths, as recognized by the lower Frequency ARray (LOFAR) in Europe. This particular interferometric network is made up of about 20,000 radio antennas, dispersed throughout fifty two locations across Europe.
Presently, LOFAR may be the sole radio telescope system capable of serious, high resolution imaging at frequencies below hundred megahertz, providing a view of the skies like absolutely no other person.
This data release, covering 4% of the northern skies, was the very first for the network ‘s ambitious plan to picture the whole northern sky in ultra-low-frequencies, the LOFAR LBA Sky Survey (LoLSS).
Since it is based on Earth, LOFAR comes with a major hurdle to get over that does not afflict space based telescopes: the ionosphere.
This’s very difficult for ultra-low-frequency radio waves, that may be mirrored back to space. At frequencies below five megahertz, the ionosphere is opaque because of this.
The frequencies which do penetrate the ionosphere is able to vary based on atmospheric conditions. In order to conquer the issue, the staff used supercomputers running algorithms to fix for ionospheric interference each 4 seconds. Over the 256 hours which LOFAR stared in the sky, that is a great deal of corrections.
This’s what has provided us with such a distinct view of the ultra-low-frequency sky.
“After years of software development, it’s really fantastic to find out this has now actually worked out,” said astronomer Huub Röttgering of Leiden Observatory in the Netherlands.
The results were published in Astronomy & Astrophysics.