Odd radio circle


In astronomy, an Odd radio circle (ORC) is a very large unexplained astronomical object that, at radio wavelengths, is highly circular and brighter along its edges.[1] As of 27 April 2021, there have been five such objects (and possibly six more) observed.[2][3][4][5][6][7][8] The observed ORCs are bright at radio wavelengths, but are not visible at visible, infrared or X-ray wavelengths.[2][3] Three of the ORCs contain optical galaxies in their centers, suggesting that the galaxies might have formed these objects.[3][8]


The ORCs were detected in late 2019 after astronomer Anna Kapinska studied a Pilot Survey of the Evolutionary Map of the Universe (EMU), based on the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope array.[9] Every detected ORC, about 1 arcminute in diameter, are some distance from the galactic plane, at high galactic latitudes. The possibility of a spherical shock wave, associated with fast radio bursts, gamma-ray bursts, or neutron star mergers, was considered, but, if related, would have to have taken place in the distant past due to the large angular size of the ORCs, according to the researchers.[5] Also according to the astronomers, "Circular features are well-known in radio astronomical images, and usually represent a spherical object such as a supernova remnant, a planetary nebula, a circumstellar shell, or a face-on disc such as a protoplanetary disc or a star-forming galaxy, ... They may also arise from imaging artefact around bright sources caused by calibration errors or inadequate deconvolution. Here we report the discovery of a class of circular feature in radio images that do not seem to correspond to any of these known types of object or artefact, but rather appear to be a new class of astronomical object."[5]

See also


  1. ^ Norris, Ray (1 December 2020). "'WTF?': newly discovered ghostly circles in the sky can't be explained by current theories, and astronomers are excited". The Conversation Australia. Retrieved 14 December 2020.
  2. ^ a b Norris, Ray P.; et al. (2021). "Unexpected Circular Radio Objects at High Galactic Latitude". Publications of the Astronomical Society of Australia. 38. arXiv:2006.14805v1. Bibcode:2021PASA...38....3N. doi:10.1017/pasa.2020.52. S2CID 220128279.
  3. ^ a b c Johnson-Groh, Mara (8 July 2020). "4 mysterious objects spotted in deep space are unlike anything ever seen". Live Science. Retrieved 9 July 2020.
  4. ^ Murugesu, Jason Arunn (3 July 2020). "Circles in space made of radio waves are like nothing we've ever seen". New Scientist. Retrieved 9 July 2020.
  5. ^ a b c Starr, Michelle (9 July 2020). "Astronomers Detect Unexpected Class of Mysterious Circular Objects in Space". ScienceAlert.com. Retrieved 9 July 2020.
  6. ^ Osborne, Hannah (9 July 2020). "'Odd' Circles of Radio Waves Coming from Unknown Cosmic Source Discovered". Newsweek. Retrieved 10 July 2020.
  7. ^ Ferreira, Becky (10 July 2020). "Scientists Discover Unexplained Glowing Circles of Energy in Space - Scientists believe they have likely discovered a new and unexplained class of space object: the Odd Radio Circle, or ORC". Vice. Retrieved 11 July 2020.
  8. ^ a b Nowakowski, Tomasz. "Astronomers discover a new extragalactic circular radio source". Phys.org. Retrieved 4 May 2021.
  9. ^ Rod, Isabelle (7 December 2020). "Astronomy: 'Odd radio circles' in the sky a 'genuine mystery'". BBC World News. Retrieved 8 December 2020.

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