Astronomers Discover Record-Breaking Double Radio Ring Halfway Across the Uni...

In a remarkable discovery that pushes the boundaries of cosmic exploration, an international team of astronomers, aided by citizen scientists, has identified the most distant and powerful "Odd Radio Circle" (ORC) ever seen. The object, designated RAD J131346.9+500320, is a colossal structure of faint radio waves featuring a rare and stunning double-ring system. The light from this object has traveled for approximately 7.7 billion years to reach Earth, meaning we are observing it as it existed when the universe was just half its current age.

The discovery was led by researchers from the University of Mumbai in partnership with the RAD@home Astronomy Collaboratory, a citizen science platform founded by astronomer Dr. Ananda Hota. Published in the journal Monthly Notices of the Royal Astronomical Society, the findings were made using the Low-Frequency Array (LOFAR), a vast pan-European network of radio antennas that is the world's most sensitive telescope at low radio frequencies. This is the first ORC to be discovered through citizen science and the first to be identified with LOFAR, highlighting a successful collaboration between professional researchers and the public.

Odd Radio Circles are a relatively new astronomical phenomenon, first detected in 2019, and are characterized as enormous, faint rings of radio emission that surround a central galaxy. They are invisible in optical light and can only be detected with highly sensitive radio telescopes. The origin of these massive structures, which can be many times the size of our own Milky Way galaxy, has been a subject of intense debate.

Leading theories point to shockwaves from merging supermassive black holes or galaxies. However, this new discovery challenges those ideas. The team behind RAD J131346.9+500320 proposes that its unique double-ring structure is the result of powerful "superwind outflows" or giant shocks emanating from the supermassive black hole at the heart of its host galaxy.

This finding provides a compelling fossil relic of past black hole activity and offers a crucial window into the co-evolution of galaxies and the cosmic giants at their centers.

The specifics of RAD J131346.9+500320 are staggering. It consists of two intersecting rings, each spanning roughly 978,000 light-years, which are themselves enveloped in a fainter halo that stretches about 2.6 million light-years across. Its immense distance and power provide an unprecedented natural laboratory for studying galactic feedback.

Galactic feedback is the process by which energy from a central black hole can influence its entire host galaxy by expelling gas and regulating star formation. Dr. Ananda Hota stated that ORCs are among the most "bizarre and beautiful cosmic structures we've ever seen" and may hold vital clues to understanding these fundamental processes.

The discovery was part of a larger survey that also uncovered two other giant radio galaxies with similar ring-like features, reinforcing the idea that these structures are part of a broader family of phenomena shaped by the complex interplay between black hole jets and their environments.

• Background on Odd Radio Circles (ORCs): First identified only six years ago, ORCs are a class of mysterious astronomical objects that are exceptionally large and faint. Visible only in the radio spectrum, they are composed of magnetized plasma and typically surround a galaxy.
• Only a handful have been confirmed to date, with most measuring 10 to 20 times the diameter of the Milky Way. Their recent discovery is a testament to the increased sensitivity of modern radio telescopes like the Australian Square Kilometre Array Pathfinder (ASKAP) and LOFAR, which can detect these ghostly structures that were previously hidden from view.
• A Landmark Citizen Science Collaboration: The discovery of RAD J131346.9+500320 is a significant achievement for citizen science. It was found by volunteers participating in the RAD@home Astronomy Collaboratory, a platform that allows the public to help professional astronomers analyze vast datasets.
• Dr. Ananda Hota, the founder of RAD@home, emphasized how this partnership can "push the boundaries of scientific discovery," allowing human pattern recognition to spot anomalies that automated algorithms might miss in the complex data from deep space surveys.
• The Power of the LOFAR Telescope: This ORC was the first to be identified using the Low-Frequency Array (LOFAR). LOFAR is a unique pan-European radio telescope that combines signals from tens of thousands of simple antennas spread across several countries, functioning as a single, giant interferometer.
• It operates at very low radio frequencies (10 to 240 megahertz), which allows it to survey vast areas of the sky and peer back billions of years into the universe's history, making it uniquely suited for finding faint, ancient structures like ORCs.
• Challenging Existing Theories of Origin: The dual-ring nature of RAD J131346.9+500320 provides strong evidence for a specific formation mechanism. While theories like shockwaves from the merger of two supermassive black holes have been proposed for other ORCs, the structure of this object points toward powerful outflows from a single active galactic nucleus.
• These "superwinds" are thought to be driven by the central black hole, creating immense shockwaves that expand into the intergalactic medium, with the double ring possibly indicating two distinct episodes of activity.
• Implications for Galaxy and Black Hole Evolution: This discovery offers critical insights into "galactic feedback," a key process in galaxy evolution. The immense energy released by a supermassive black hole can blow gas out of a galaxy, which can halt star formation.
• The rings of this ORC are essentially a fossil record of such an event that occurred billions of years ago. Studying its size and energy helps astronomers understand the scale of these feedback mechanisms and how black holes and their host galaxies grow and regulate each other over cosmic timescales.
• A Broader Family of Cosmic Structures: In the same study, the research team identified two other giant radio galaxies, RAD J122622.6+640622 and RAD J142004.0+621715, which also exhibit unusual ring-like structures associated with their black hole jets. One features a jet that appears to bend sharply before blowing a spectacular radio ring.
• According to astrophysicist Pratik Dabhade, these discoveries suggest that ORCs are not just isolated oddities but are part of a larger class of "exotic plasma structures shaped by black hole jets, winds, and their environments."
• Future Research and Next Steps: The discovery of this record-breaking ORC will trigger extensive follow-up observations. Astronomers will likely use other powerful instruments, such as optical and infrared telescopes, to study the central host galaxy in greater detail.
• Future radio telescopes like the Square Kilometre Array (SKA) are expected to uncover many more of these objects. Building a larger sample of ORCs will allow scientists to better classify them and test their models of how these colossal radio rings form and evolve throughout the universe's history.