RAD J131346.9+500320
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 RAD J131346.9+500320 is an example of an 'odd radio circle' (ORC). It is the most distant and powerful ORC yet found. | |
| Object type | Odd radio circle |
|---|---|
Observation data (Epoch J2000) | |
| Constellation | Canes Venatici |
| 13h 13m 51s | |
| Declination | +50° 04′ 00″ |
| Distance | 7.7 billion light years |
RAD J131346.9+500320 (RAD J131346) is an odd radio circle (ORC) located in the constellation Canes Venatici approximately 7.7 billion light-years from Earth. It consists of two intersecting rings, each spanning 300,000 light-years, surrounded by an even larger radio cloud extending nearly 3 million light-years. It is the most distant and powerful ORC yet observed, and is the first ORC identified through citizen science collaboration.[1][2][3][4]
Citizen science breakthrough
RAD J131346 was discovered on June 11, 2024, during an online training session of the RAD@home Astronomy Collaboratory, a pioneering citizen science initiative based in Mumbai, India. The discovery emerged through visual inspection of low-frequency continuum maps from the LOFAR Two-metre Sky Survey (LoTSS) DR2, when participants identified two intersecting ring-like structures centered on a compact radio core.[4] Founded in 2013 by Dr. Ananda Hota, the platform operates under zero-funding, zero-infrastructure.[5][6][7][8]
LOFAR telescope observations
The detection was made possible through the Low Frequency Array (LOFAR), the world's largest and most sensitive radio telescope operating at low frequencies between 10 and 240 MHz. LOFAR consists of 52 antenna stations distributed across eight European countries, creating a pan-European interferometer with unparalleled sensitivity and angular resolution at these frequencies.[9][10][11][12]
LOFAR's innovative design utilizes thousands of simple antennas without moving parts, with signals digitally combined in software to create radio images. This revolutionary approach provides more than two orders of magnitude better sensitivity than previous telescopes at these frequencies, making it ideally suited for detecting faint, extended radio structures like ORCs.[9][10][12]
Physical characteristics and structure
Ring system properties
RAD J131346 exhibits a double-ring morphology, with each ring measuring approximately 300 kiloparsecs (approximately 978,000 light-years) in diameter. The entire structure extends over 800 kiloparsecs (2.6 million light-years), embedded within diffuse emission that rivals the size of giant radio galaxies.[4][13]
The twin rings display mild brightness enhancements at their intersection points, suggesting complex interaction between the overlapping structures. This configuration represents only the second known example of an ORC with intersecting rings, making it exceptionally rare among the handful of confirmed ORCs discovered to date.[4]
Spectral analysis and power
Detailed spectral analysis reveals steep radio spectra with spectral indices of α54144 = 1.22 ± 0.15 and α1441400 = 1.20 ± 0.10. These consistently steep values across a wide frequency range support interpretation of the emission as aged synchrotron plasma, characteristic of relic emission rather than ongoing jet activity.[4]
The integrated radio luminosity reaches 2.27 × 1026 W Hz−1 at 144 MHz, making it nearly two orders of magnitude more powerful than other known ORCs, which typically exhibit luminosities in the range 1023–1024 W Hz−1. This power, combined with its high redshift of z ≈ 0.94, establishes RAD J131346 as both the most distant and most powerful ORC identified to date.[4][1][14]
