Incredibly, this image above shows no starry sky. Instead, each white dot is a supermassive black hole at the core of a different galaxy. This remarkable collection made up of radio waves emitted by matter orbiting distant and huge black holes, not by visible light, and it is the most detailed sky map among the low radio frequencies. A system of 52 stations spread across nine European countries: Germany, the Netherlands, Poland, France, the United Kingdom, Sweden, Ireland, Latvia and Italy collected radio observations by the LOWUCT array (LOFAR). Together they are the world’s largest combined radio telescope.
“This is the result of many years of working with incredibly solid data. We had to invent new methods to convert radio signals into images of the sky,” said Dr. A.S. Francesco de Gasperin said in a statement. The data collected covered 4 percent of the northern half of the sky and was just the beginning of an ambitious program to map the entire northern sky. As reported in Astronomy and Astrophysics, the program will help answer questions of various sizes, from the magnetic universe of exoplanets to the distribution of galaxies in the universe.
The observations that are conduct are as low radio frequencies. Long radio wavelengths greatly influenced by the layer of electrically charged particles surrounding our planet by the ionosphere. The layers that make up the free electrons are not good for these radio observations because their motion affects the quality of what astronomers can observe. “It’s the same when you try to see the world immersed in a swimming pool. When you look, the waves on the pool water develop light and distort the vision, “explained Leanne Observatory co-author Rainout Van Weeren.
Correcting the effects of the ionosphere was not an easy task. The researchers had to use a supercomputer that could do just that every 4 seconds. Given this map of 256 hours of observation, you can imagine how challenging it was. “After so many years of software development, it’s been so amazing to see that it really works now,” said Hub Röttgering, scientific director at Leiden Observatory. Defined black holes do not scatter light, so it is incredible that this map lets us see something that is fifth invisible. It is amazing to see 25,000 of them at once.