Astronomers Have Discovered Mysterious Round Objects In Space
Analysis of radio telescope observations allowed scientists to detect a previously unknown type of space object. Rounded in shape and brighter at the edges-astrophysicists suggest that these are traces of shock waves from some colossal events outside the Galaxy. The results of the study have been prepared for publication in the journal Nature Astronomy and are available on the website arXiv.org.
In late 2019, the ASKAP (Australian Square Kilometer Array Pathfinder) radio telescope complex — one of the most sensitive in the world — detected three strange circular objects while collecting data for an Evolutionary map of the Universe (EMU).
A new type of signal has puzzled astronomers: they were visible only in radio waves and were not detected in the x-ray, optical, or infrared bands. They were called "strange radio Circles," or" orcs " (ORC — Odd Radio Circles).
Later, the existence of two of the three objects — ORC 1 and ORC 2 — was confirmed by observations on the Australian Compact Array radio telescope, and another, the fourth, was found in archived data collected by the Giant MetreWave radio telescope in 2013, several years before the inclusion of ASKAP.
The objects are shaped like circles or bubbles, and three of them are particularly bright at the edges. Scientists led by astrophysicist ray Norris from the University of Western Sydney (Australia) believe that they have discovered a new class of astronomical objects.
"Here we report the detection of circular shapes in radio images that do not correspond to any of the known types of objects or artifacts. This phenomenon appears to be a new class of astronomical objects," the researchers write.
They discuss other hypotheses, assuming that "orcs" may be unusual manifestations of previously known objects: "Circular elements in radio astronomy images usually represent spherical objects, such as supernova remnants, planetary nebulae, near-star shells, protoplanetary disks, or star-forming galaxies."
However, only two orcs have an optical galaxy near the center of radio emission, and the other two are not associated with a galactic activity. In this case, ORC 3 looks like a uniform disk, while the other three look more like a ring. Their radio spectral index does not match the index of planetary nebulae, and there are too many of them for supernova remnants — the EMU project has only examined a very small section of the sky and has already detected three orcs, and supernova remnants are much rarer.
All four objects are located in high galactic latitudes, at some distance from the plane of the Galaxy. Their angular diameter is about a minute — about three percent of the size of the moon in the night sky. But since the distance to them is unknown, it is problematic to talk about the actual size. According to the authors, "orcs" are giant spherical shock waves from some large-scale events outside the milky Way.
"Several such classes of transients capable of generating spherical shock waves have recently been discovered, such as fast radio bursts, gamma-ray bursts, and neutron star mergers. It is also possible that orcs represent a new category of a known phenomenon, such as jets of radio galaxies or blazars. However, due to the large angular size of the ORC, any of these transients must have occurred in the very distant past," the researchers write.
Scientists note that new observations are needed to understand the nature of "orcs."