Astronomers find most distant odd radio circle
Astronomers have discovered the most distant and powerful odd radio circle, a massive double-ringed radio structure nearly 10 billion years old. Using citizen science and the LOFAR telescope, researchers propose these cosmic rings form from galactic superwinds rather than black hole mergers. The finding challenges existing theories and highlights the role of human pattern recognition in astronomy.
Odd radio circles (ORCs) are enormous, faint, ring-shaped structures of radio emission surrounding galaxies, visible only in the radio band and consisting of relativistic, magnetized plasma. Detected for the first time just six years ago, only a handful of confirmed examples exist, most measuring 10-20 times the size of the Milky Way galaxy.
Previous research suggested ORCs might result from shockwaves of merging supermassive black holes or galaxies. However, a new study published on October 2 in Monthly Notices of the Royal Astronomical Society proposes they link to superwind outflows from spiral host radio galaxies. Led by researchers from the University of Mumbai, the discovery utilized the RAD@home Astronomy Collaboratory citizen science platform and the Low-Frequency Array (LOFAR), the world's largest low-frequency radio telescope operating at 10 to 240 megahertz.
The source, RAD J131346.9+500320, lies at redshift ~0.94, when the universe was half its current age, making it the most distant and powerful ORC known. It features two intersecting rings, only the second such example identified. Dr. Ananda Hota, founder of RAD@home, said: "This work shows how professional astronomers and citizen scientists together can push the boundaries of scientific discovery. ORCs are among the most bizarre and beautiful cosmic structures we've ever seen - and they may hold vital clues about how galaxies and black holes co-evolve, hand-in-hand."
This marks the first ORC found through citizen science and with LOFAR, a pan-European telescope with antennas across the Netherlands and other countries. Alongside it, RAD@home identified two other cosmic structures: RAD J122622.6+640622, a galaxy nearly three million light-years across—more than 25 times the Milky Way's size—with a bent jet forming a 100,000 light-year-wide radio ring; and RAD J142004.0+621715, spanning 1.4 million light-years with a similar ring at one jet's end.
All three reside in galaxy clusters weighing about 100 trillion solar masses, where jets interact with hot thermal plasma, shaping these structures. Co-author Dr. Pratik Dabhade noted: "These discoveries show that ORCs and radio rings are not isolated curiosities - they are part of a broader family of exotic plasma structures shaped by black hole jets, winds, and their environments. The fact that citizen scientists uncovered them highlights the continued importance of human pattern recognition, even in the age of machine learning."
Future telescopes like the Square Kilometre Array, along with optical surveys from DESI and LSST, promise more insights into ORC formation.