For centuries, we looked at the night sky and it seemed relatively simple: thousands of stars visible to the naked eye and, thanks to telescopes, millions of galaxies. But most of the universe remains hidden from our eyes. Many of its most violent and energetic phenomena do not emit visible light, but rather radiation at other wavelengths. If we add to that that About 95% of the universe is made up of dark matter and energy (impossible to see), it is logical that the cosmos is not shown in all its splendor. But…
Now, a new cosmic map has revealed a part of that invisible universe and has brought to light 13.7 million objects that previously remained hidden. The breakthrough comes from a huge international project based on the European Low-Frequency Array radio telescope. Using this network of antennas distributed across several countries in Europe, astronomers have created the largest and most detailed radio map of the sky ever made, part of the so-called LOFAR Two-meter Sky Survey. The result has been published in Astronomy & Astrophysics.
The map contains signals from 13.7 million cosmic sources, from distant galaxies to supernova explosions to giant jets of matter ejected by supermassive black holes. Most telescopes observe the universe in visible light, the same light that our eyes perceive. But Many of the most energetic processes in the cosmos produce radiation in radio waves, invisible to us.
When extremely energetic particles move at high speed within magnetic fields, something common near black holes or in galaxies with intense star formation, they generate powerful radio emissions. Detecting them allows Astronomers observe cosmic processes that would otherwise remain hidden. That is why radio maps can show a completely different universe. Where an optical telescope sees a quiet galaxy, a radio telescope can reveal gigantic jets of particles extending millions of light years, fed by a central black hole.
The instrument responsible for this new map, LOFAR, is one of the largest and most sensitive radio telescopes in the world. It is not a single telescope, but a network of 52 stations distributed across eight European countries. (Spain is not among them), connected to each other to function as a gigantic virtual instrument thousands of kilometers in diameter.
Thanks to this technique, called interferometry, scientists can capture extremely weak radio signals from very distant galaxies. Building the map has been a huge technological challenge. Astronomers had to process more than 13,000 hours of observations, correct distortions caused by the Earth’s ionosphere and manage gigantic volumes of data using supercomputers.
Among the millions of objects detected, some of the most spectacular phenomena in the universe appear: colliding galaxies, remains of stellar explosions and enormous radio structures powered by supermassive black holes. Many of these structures have never been observed in such detail. Some are so gigantic that their radio emissions extend millions of light years into space, far beyond the visible limits of their galaxies.
The new map will also help study more subtle phenomena, such as the magnetic fields of the Milky Way, shock waves in galaxy clusters or even the interaction between stars and planets in distant systems. For astronomers, this catalog is a gold mine. With millions of registered objects, scientists will be able to search for rare or unknown phenomena, study the evolution of galaxies and better understand the role of black holes in the history of the cosmos. And this is just the beginning: the project is already working on an update to the system, known as LOFAR 2.0, which will allow mapping the sky even faster and with higher resolution.