This strange radius circle, called ORC J0102-2450, is one of those space blob-like structures that astronomers had previously discovered. What are they? According to experts, who publish their study in the journal MNRAS Letters, these objects could be related in some way to galaxies.
The space still houses a wealth of secrets. These mysterious structures, called odd radius circles or ORCs, were only discovered last year precisely in a series of observations carried out in 2019 at the Australian Square Kilometer Array Pathfinder (ASKAP, a radio telescope array located at the Radio Astronomy Observatory of Murchison -MRO- in the Midwest of Australia), which is one of the most sensitive radio telescopes in the world.
These cosmic structures are apparently giant circles of light that are relatively faint at radio wavelengths, which appear brighter around the edges, as if they were bubbles from space. Astronomers cannot make them fit into any phenomenon known so far even though circular objects are relatively common in space. ORCs are unlike anything we know of.
Follow-up observations with a set of telescopes other than ASKAP confirmed the presence of two of the three original ORCs ; and, a little later, a fourth was discovered in the data collected by another instrument. So it is clear that the finding of these ghostly circles is not the product of any error, failure or local phenomenon of the telescope, as it has been corroborated with other instruments as we have seen.
Since we don’t know how far the ORCs are, it is quite difficult to measure their size. That’s where ORC J0102-2450, the last odd radius circle makes its stellar appearance, pun intended.
The SKAP radio telescope array conducted a series of continuous radio observations between 2019 and December 2020 with a team led by astronomer Bärbel Koribalski from CSIRO and the University of Western Sydney (Australia). The researchers combined eight of the continuous radio images, a process that reveals objects too faint to be seen in just one or two images. From the combined data, a faint ring emerged. Contrasting it with observations from other studies revealed no radiation at other wavelengths, which may help rule out some emission sources.
What they did find, almost in the center of the ORC, was an elliptical radio galaxy, called DES J010224.33-245039.5. A coincidence? But two of the other four ORCs described last year also had an elliptical radio galaxy burst right in the middle. This suggests that the circles may have something to do with elliptical radio galaxies.
Although the sample size is still extremely small, we cannot take anything for granted, but we can head in certain promising directions for future observations and analysis.
“The discovery of more ORCs in the rapidly growing amount of continuous wide-field radio data from ASKAP and other telescopes will show whether the above scenarios have any merit, contributing to exciting times in astronomy,” the authors wrote.
Referencia: Discovery of a new extragalactic circular radio source with ASKAP: ORC J0102-2450 Baerbel S. Koribalski, Ray P. Norris, Heinz Andernach, Lawrence Rudnick, Stanislav Shabala, Miroslav Filipovic, Emil Lenc MNRAS Letters 2021 arXiv:2104.13055v1
