They look like stars, but this photo taken by NASA shows something truly massive and terrifying – teach me about science

The image may look completely ordinary and appear to contain thousands of stars, but in reality they are supermassive black holes. Surprisingly, it is a map of the sky showing more than 25,000 supermassive black holes. Each black hole is located in a different, distant galaxy.

An international group of astronomers published in early 2021 in the journal Astronomy and astrophysics, a map of the sky showing 25,000 black holes, making it the most detailed ever seen in the field of so-called low radio frequencies. The map is the result of 256 hours of observations of the northern sky, using data from the Low Frequency Observatory (LOFAR) in Europe. This interferometry network consists of about 20,000 radio antennas, distributed among 52 stations spread across nine European countries.

“This is the result of many years of working with very difficult data. “We had to invent new ways of converting radio signals into images of the sky.” He said in a statementDirector of the investigation, Francesco De Gasperin.

at the moment, Lofar It is the largest radio telescope that operates at the lowest frequencies that can be observed from Earth. Unlike single-dish telescopes, LOFAR is a multi-purpose sensor network, with innovative computing and networking infrastructure that can handle very large amounts of data.

Since this is not a space telescope, but rather makes its observations from the surface, it has significant challenges to overcome. The main reason is the ionosphere that surrounds the Earth – a layer of free electrons that obscures telescopes – which makes it difficult to track black holes.

“It’s like trying to see the world while you’re immersed in a swimming pool. “When you look up, the waves of the pool water bend the light rays and distort your vision.” He explains Co-author Renaut van Wieren (Leiden Observatory).

The frequencies that penetrate the ionosphere can vary depending on atmospheric conditions. In order to successfully complete the mission, the team used supercomputers that ran algorithms to correct ion interference every four seconds. Throughout the 256 hours that Lovar spent observing the sky, there were many corrections.

When you hear the phrase “25,000 supermassive black holes,” there’s probably a large number and a large area that comes to mind, and that’s what happens. However, the map covers only 4% of the northern half of the sky. Astronomers plan to continue until the entire northern sky is mapped. In addition to supermassive black holes, the map also provides information about the large-scale structure of the universe, among other things.

More detailed research could allow the study of more than a million low-frequency radio spectra, providing unique insights into physical models of galaxies, active nuclei, galaxy clusters and other areas of research. “This experiment represents a unique attempt to explore the very low-frequency sky with high angular resolution and depth.” They wrote Authors of the article.

The study is detailed in an article published in Astronomy and astrophysics.