In 2020, Australian astronomers discovered some of the most mysterious objects in the universe using the ASKAP (Australian Square Kilometre Array Pathfinder) telescope - “orcs” (Odd Radio Circles, ORC), or “strange radio circles”. These smoke ring-like objects were strikingly different from anything previously known to science, and were more like a visual effect. However, further study showed that they are quite real, and that there are more than a thousand of them in the sky. The huge rings span about 1 million light-years across. They are only visible in radio waves and are not detectable in X-ray, optical, or infrared.
A new study by the same team of astronomers at the MeerKAT telescope has shown that strange radio circles could be coming from giant black holes. It is reported by LiveScience. Astronomers have observed five orcs and found that at least three of them are looped around galaxies with supermassive black holes, the mass of which is millions and billions of times greater than the mass of the Sun. Such black holes often eject powerful streams of matter, and orcs can appear as a result of this giant galactic explosion. Radio circles are shock waves that accelerate electrons in a layer of rarefied gas located behind the center of a black hole and pull them out of atoms, creating a magnetic field around which charged electrons circle, emitting radio waves.
What exactly is the cause of the explosion, the researchers do not yet know. This requires even more sensitive telescopes. This is likely to become a reality when the Square Kilometer Array (SKA) is put into operation - the world's largest network of radio telescopes in Australia and South Africa, which South Africa, Australia, the UK, France, Canada, China, India and several other countries plan to launch by 2028.