The image above may look like a normal image in the night sky, but what you see is more than just shining stars. Each of these white dots is an active supermassive black hole.
And each of these black holes swallows the matter in the center of the Milky Way galaxy millions of light-years away. This is how all these black holes can be precisely located.
Astronomers have drawn a total of 25,000 such points, creating the most detailed map of black holes at low radio frequencies to date. This achievement took many years and required European-sized radio telescopes to compile.
Astronomer Francesco de Gasperin of the University of Hamburg, Germany, explained: “This is the result of many years of research on incredible data.” “We must invent new methods. Convert radio signals into sky images.”
When they are just wandering, black holes do not emit any detectable radiation, which makes them harder to detect. When a black hole is actively absorbing matter-winding it in from a circle of dust and gas, like water circling a drain pipe, it is hovering in it-strong force generates radiation that spans multiple wavelengths, we can Detected in a wide space.
The picture above is so special because it covers the ultra-low radio wavelengths detected by the European Low Frequency Radar (LOFAR). This interference network consists of approximately 20,000 radio antennas distributed in 52 locations throughout Europe.
Currently, LOFAR is the only radio telescope network capable of deep, high-resolution imaging at frequencies below 100 MHz, providing an unparalleled view of the sky. The data release covers 4% of the northern sky, which is the first plan in the network’s ambitious plan to image the entire northern sky with ultra-low frequency LOFAR LBA Sky Survey (LoLSS).
Because it is based on the earth, LOFAR does have a big obstacle to overcome. It will not affect space-based telescopes: the ionosphere. This is especially problematic for ultra-low frequency radio waves, because ultra-low frequency radio waves can be reflected back into space. Therefore, at frequencies below 5 MHz, the ionosphere is opaque.
The frequency that does penetrate the ionosphere varies according to atmospheric conditions. To overcome this problem, the research team used a supercomputer to run an algorithm to correct for ionospheric interference every four seconds. LOFAR stared at the sky for 256 hours, which is a lot of correction.
This is our clear understanding of the ultra-low frequency sky.
Huub Röttgering, an astronomer at Leiden Observatory in the Netherlands, said: “After years of software development, it’s really great, really great.”
The ionosphere must also be corrected for another benefit: it will allow astronomers to use LoLSS data to study the ionosphere itself. LoLSS can be used to describe the ionospheric traveling waves, scintillation and the relationship between the ionosphere and the solar cycle in more detail. This will allow scientists to better constrain the ionospheric model.
The survey will also provide new data on various astronomical objects and phenomena, as well as objects that may not be discovered or explored in areas below 50 MHz.
The researchers wrote in the paper: “The final version of this survey will promote a series of advances in astronomy research.”
“[This] It will allow the study of more than one million low-frequency radio spectrums, thereby providing unique insights into physical models of galaxies, active nuclei, galaxy clusters and other research fields. This experiment represents a unique attempt to explore the ultra-low frequency sky at high angular resolution and depth. “
The result will be in Astronomy and Astrophysics.