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"ORCs" redirects here. For the singular form, see orc (disambiguation).

Image of Odd radio circle ORC J2103-6200 by the MeerKAT telescope superimposed on an optical image from the Dark Energy Survey (2022)[1][2]

In astronomy, an odd radio circle (ORC) is a very large (over 50 thousand times the diameter of our Milky Way ~ 3 million light years) unexplained astronomical object that, at radio wavelengths, is highly circular and brighter along its edges.[3] As of 27 April 2021, there have been five such objects (and possibly six more) observed.[4][5][6][7][8][9][10] The observed ORCs are bright at radio wavelengths, but are not visible at visible, infrared or X-ray wavelengths. This is due to the physical process producing this radiation, which is thought to be synchrotron radiation.[4][5] Three of the ORCs contain optical galaxies in their centers, suggesting that the galaxies might have formed these objects.[5][10]

Description

Artist’s impression of an odd radio circle exploding from a central galaxy. ORCs can expand past other galaxies.[1][2]
Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope array

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.[11] All of the ORCs are about 1 arcminute in diameter, and 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.[7] 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. This class of circular feature in radio images does not seem to correspond to any of these known types of object or artefact, but rather appears to be a new class of astronomical object."[7]

See also

References

  1. ^ a b Norris, Ray P; Collier, J D; Crocker, Roland M; Heywood, Ian; Macgregor, Peter; Rudnick, L; Shabala, Stas; Andernach, Heinz; da Cunha, Elisabete; English, Jayanne; Filipović, Miroslav (24 March 2022). "MeerKAT uncovers the physics of an Odd Radio Circle". Monthly Notices of the Royal Astronomical Society. 513: 1300–1316. arXiv:2203.10669. doi:10.1093/mnras/stac701. ISSN 0035-8711.
  2. ^ a b Norris, Ray (21 March 2022). "'Odd radio circles' that baffled astronomers are likely explosions from distant galaxies". The Conversation. Retrieved 30 March 2022.
  3. ^ 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.
  4. ^ 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.
  5. ^ 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.
  6. ^ 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.
  7. ^ a b c Starr, Michelle (9 July 2020). "Astronomers Detect Unexpected Class of Mysterious Circular Objects in Space". ScienceAlert. Retrieved 9 July 2020.
  8. ^ Osborne, Hannah (9 July 2020). "'Odd' Circles of Radio Waves Coming from Unknown Cosmic Source Discovered". Newsweek. Retrieved 10 July 2020.
  9. ^ 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.
  10. ^ a b Nowakowski, Tomasz (4 May 2021). "Astronomers discover a new extragalactic circular radio source". Phys.org. Retrieved 4 May 2021.
  11. ^ Rod, Isabelle (7 December 2020). "Astronomy: 'Odd radio circles' in the sky a 'genuine mystery'". BBC World News. Retrieved 8 December 2020.


source: https://en.wikipedia.org/wiki/Odd_radio_circle

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