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Unexplained circular astronomical object detected only by radio waves
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
^
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 .
^
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 .
^ 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 .
^
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 .
^
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 .
^ 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 .
^
a
b
c Starr, Michelle (9 July 2020).
"Astronomers Detect Unexpected Class of Mysterious Circular Objects in Space" . ScienceAlert . Retrieved 9 July 2020 .
^ Osborne, Hannah (9 July 2020).
" 'Odd' Circles of Radio Waves Coming from Unknown Cosmic Source Discovered" .
Newsweek . Retrieved 10 July 2020 .
^ 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 .
^
a
b Nowakowski, Tomasz (4 May 2021).
"Astronomers discover a new extragalactic circular radio source" . Phys.org . Retrieved 4 May 2021 .
^ Rod, Isabelle (7 December 2020).
"Astronomy: 'Odd radio circles' in the sky a 'genuine mystery' " . BBC World News . Retrieved 8 December 2020 .
External links
Concepts
Radio telescopes (
List )
Individual telescopes Interferometers
Allen Telescope Array (ATA, California, US )
Atacama Large Millimeter Array (ALMA, Chile )
Australia Telescope Compact Array (ATCA, Australia )
Australian Square Kilometre Array Pathfinder (ASKAP, Australia )
Canadian Hydrogen Intensity Mapping Experiment (CHIME, Canada )
Combined Array for Research in Millimeter-wave Astronomy (CARMA, California, US )
European VLBI Network (Europe)
Event Horizon Telescope (EHT)
Giant Metrewave Radio Telescope (GMRT, India )
Green Bank Interferometer (GBI, West Virginia, US )
Korean VLBI Network (KVN, South Korea )
Large Latin American Millimeter Array (LLAMA, Argentina/Brazil )
Long Wavelength Array (LWA, New Mexico, US )
Low-Frequency Array (LOFAR, Netherlands )
MeerKAT (South Africa )
Molonglo Observatory Synthesis Telescope (MOST, Australia )
Multi-Element Radio Linked Interferometer Network (MERLIN, UK )
Murchison Widefield Array (MWA, Australia )
Northern Cross Radio Telescope (Italy )
Northern Extended Millimeter Array (France )
One-Mile Telescope (UK)
Primeval Structure Telescope (PaST, China )
Square Kilometre Array (SKA, Australia, South Africa )
Submillimeter Array (SMA, US )
Very Large Array (VLA, New Mexico, US )
Very Long Baseline Array (VLBA, US )
Westerbork Synthesis Radio Telescope (WSRT, Netherlands )
Space-based
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