The image above may look like a fairly normal picture of the night sky, but what you see is much more special than just the shining stars. Each of these white dots is an active supermassive black hole.
And each of those black holes lifts the material into the heart of a galaxy millions of light years away – the same way they can be relaxed.
With a total of 6,000,000 such points, astronomers have mapped the most detailed map of black holes to low radio frequencies, an achievement that took years to compile a European-sized radio telescope.
“This is the result of many years of work on incredibly difficult data,” explained Francisco de Gasperin, an astronomer at the University of Hamburg in Germany. “We had to find new ways to convert radio signals into sky images.”
When they stop working, the black holes do not detect any radiation, making them more difficult to detect. When a black hole material is actively working – spoling it with a disk of dust and gas that drains as much water as it does – the compressive forces involved produce radiation in multiple wavelengths that we can detect in the vastness of space.
Discovered by LOW Frequency Array (LOFAR) in Europe, what makes the image above special is that it covers ultra-low radio wavelengths. This interferometric network includes about 20,000 radio antennas, distributed in 52 locations across Europe.
Currently, Loafer is the only radio telescope network capable of deep, high-resolution imaging at frequencies below 100 MHz, with no view of the sky. The data release, covering four percent of the northern sky, is the first plan to create an image of the entire northern sky Ultra-Low-Frequencies, LOFAR LBA Sky Survey (LLSS) for the network’s ambitious plan.
Because it is based on Earth, LOFAR has a significant barrier in space that does not affect a space-based telescope: the ionosphere. This is especially problematic for ultra-low-frequency radio waves, which can be reflected back into space. At frequencies below 5 MHz, the ionosphere is opaque for this reason.
The frequency entering the ionosphere can vary according to atmospheric conditions. To overcome this problem, the team used a supercomputer running algorithms to correct ionospheric interference every four seconds. In the 256 hours that LOFAR looked at the sky, that’s a lot of improvements.
This is what has given us a clear view of the ultra-low-frequency sky.
“After so many years of software development, it’s amazing to see,” said Hub Röttering, an astronomer at the Leiden Observatory in the Netherlands.
There is another advantage to improving the ionosphere: it will allow astronomers to use LLSS data to study the ionosphere. The relationship of the ionosphere with ionospheric travel waves, scintillations and the solar cycle can be characterized in much more detail with LLSS. This will allow scientists to better control ionospheric models.
And the survey will provide new data on all types of astronomical objects, objects and phenomena, as well as objects that may be unknown or discovered in the field below 50 MHz.
“The final publication of the survey will facilitate the advancement in various fields of astronomical research,” the researchers wrote in their paper.
“[This] To provide unique insights for physical models for galaxies, active nuclei, galaxy clusters, and other areas of research, will allow the study of less than 1 million low-frequency radio spectra. This experiment represents a unique attempt to explore ultra-low frequency skies at high angular resolution and depth. “
The results are about to be published Astronomy and Astrophysics.