The discovery of an enormous , ghostly circle in extragalactic space is bringing us closer to understanding what these mysterious structures actually are.
The so-called odd radio circle, named ORC J0102-2450, joins just a couple of previously discovered space blobs. Given the low sample size, the new discovery adds important statistical data that suggest these objects could somehow be associated with galaxies. The paper has been accepted into MNRAS Letters, and is out there on preprint server arXiv.
Humanity has been staring up and wondering about the sky for tens of thousands of years, but however , space retains many secrets. Odd radio circles – ORCs – were only discovered last year, in 2019 observations collected by the Australian Square Kilometre Array Pathfinder (ASKAP), one among the world’s most sensitive radio telescopes.
As the name suggests, they’re apparently giant circles of relatively faint light in radio wavelengths, appearing brighter round the edges, like bubbles. Although circular objects are relatively common in space, the ORCs appeared to correspond with no known phenomenon.
Follow-up observations with different telescope array confirmed the presence of two of the first three ORCs, while a fourth was soon found in data collected by yet one more instrument. So, we will be pretty confident these aren’t the results of some ASKAP glitch or artifact, or a phenomenon local to the telescope (like the Murriyang microwave oven) either.
We don’t know how distant the ORCs are, which makes their size hard to measure , but finding more of them could give us more clues. That’s where ORC J0102-2450 enters the image.
ASKAP conducted a series of radio continuum observations between 2019 and December 2020. to seek out the ORC, a team led by astronomer Bärbel Koribalski of CSIRO and Western Sydney University in Australia combined eight of the radio continuum images, a process that reveals objects too faint to be seen in only one or two images.
From the combined data, a faint ring emerged. Comparison with observations from other surveys revealed no radiation in other wavelengths than radio, which may help rule out some sources of the emission.
Interestingly, however, almost bang within the center of the ORC, the team found something: an elliptical radio galaxy, named DES J010224.33-245039.5.
Sure, this might be a coincidence – but two of other four ORCs described last year also had an elliptical radio galaxy bang within the middle. The probability of finding a radio signal source randomly coincident with the middle of an ORC is one during a few hundred, the researchers said – never mind finding three of the items .
This suggests that the circles may have something to try to to with elliptical radio galaxies. we all know that radio galaxies often have radio lobes, huge elliptical structures that only emit in radio wavelengths ballooning out on either side of the galactic nucleus. One possibility is that the ORCs are these lobes viewed end-on, in order that they seem circular.
The ORCs could also, the researchers noted, be the merchandise of an enormous shock wave from the central galaxy, but it might need to be truly giant, produced by something just like the merger of two supermassive black holes.
If either of those scenarios is that the case, the link with the galaxy can help us compute the dimensions of the ORC. within the case of ORC J0102-2450, we all know the distance to DES J010224.33-245039.5. That distance gives us a rough size estimate for ORC J0102-2450 of around 980,000 light-years. If this size is confirmed, it could help us to find out more about radio lobes or blast waves.
The third possibility the researchers considered is an interaction between a radio galaxy and therefore the intergalactic medium, possibly involving DES J010224.33-245039.5, although this seemed relatively unlikely to be ready to produce the observed ring, the team noted.
Although the sample size remains extremely small, and that we can’t tell anything for-sure to say just yet, discovery of ORC J0102-2450 points to some promising directions for future observation and analysis.
If we will find even more ORCs, they ought to be ready to help astronomers determine how common they’re , and find more similarities between them that would further narrow down their potential formation mechanisms.
Low-frequency radio observations and X-ray observations are going to be of particular interest, they noted.
“The discovery of further ORCs within the rapidly growing amount of wide-field radio continuum data from ASKAP and other telescopes will show if the above scenarios have any merit, contributing to exciting times in astronomy,” the team wrote in their paper.
The paper accepted into MNRAS Letters, and is available on arXiv.