Are Odd Radio Circles Ghosts of Ancient Black Hole Storms?

What if the Universe kept a scrapbook of past black hole storms—etched not in light, but in ghostly radio rings? Welcome, friends of the sky, to FreeAstroScience.com. Today, we follow three rare radio structures that bend our models and spark our curiosity. We’ll keep the science clear, the story human, and the facts tight. If you stay with us to the end, you’ll walk away with a deeper sense of how galaxies breathe, fight, and evolve—and how citizens and scientists together can reveal the hidden weather of the cosmos. Read on.

Are we seeing the afterglow of ancient feedback?

We’ve just met a cosmic oddity that’s both beautiful and baffling: a double-ring Odd Radio Circle (ORC) named RAD J131346.9+500320. It sits nearly 7.7 billion light-years away (z ≃ 0.94), and it’s the most distant and most powerful ORC known so far. Each ring is roughly 978,000 light-years across, nested within a faint halo about 2.6 million light-years wide—vast, delicate, and old. Its radio spectrum is steep, a classic sign of fading, relic synchrotron plasma. In short: we’re likely seeing fossil radio bubbles, re-lit by later shocks or winds tied to a central supermassive black hole. That’s the leading picture right now, and the numbers are jaw-dropping: a 144 MHz radio power of 2.27 × 10^26 W Hz−1 and a spectral index around 1.2. This thing is a heavyweight among ORCs, by nearly two orders of magnitude in power compared to typical cases. And yes, it has two intersecting rings—a rarity even among rare objects.

We don’t stumble on ORCs every day. So far, the counts hover around “a dozen or so,” and only two of them show a double-ring structure like this one. The working suspects remain supermassive black hole activity, galaxy-scale superwinds, and merger-driven shocks—processes energetic enough to light up giant, ring-like shells in radio and then let them fade for eons.

What exactly did RAD@home and LoTSS uncover?

Here’s the short version, with specifics you can hold onto.

• The object: RAD J131346.9+500320 (an Odd Radio Circle with two rings).
• Distance: photometric redshift zphot = 0.937 ± 0.045; light traveled ~7.7 billion years.
• Size: each ring 300 kpc across (978,000 ly); faint halo 800 kpc (2.6 million ly).
• Power: P144 MHz ≈ 2.27 × 10^26 W Hz−1; steep spectrum α ≈ 1.2 from 54–144–1400 MHz.
• Status: Most distant and most powerful ORC to date; first clear ORC identified in LoTSS.
• Likely origin: relic synchrotron emission, revived by shocks or a bipolar superwind tied to the host galaxy’s black hole.

And the story broadens. The same citizen science team, RAD@home, found two companion cases that aren’t ORCs but do show striking radio rings—one at the end of a diverted backflow in a giant radio galaxy, and one at the end of a filamentary jet near a cluster galaxy. These add crucial context. They hint that rings can form through different pathways, shaped by environment, jet deflection, and even galaxy–jet encounters.

Three radio rings, one story of feedback?

Let’s tour the trio, because comparison is our best teacher.

• Case A — The double-ring ORC fossil (RAD J131346.9+500320)

  • Class: Odd Radio Circle, with two intersecting rings.
  • Redshift and environment: zphot ≃ 0.937 ± 0.045; embedded in a group/poor cluster at similar redshift.
  • Radio properties:
    • LoLSS (54 MHz): 143 ± 16 mJy; LoTSS (144 MHz): 43.2 ± 4.1 mJy; NVSS (1.4 GHz): 2.8 ± 0.6 mJy.
    • Spectral index: α54→144 ≈ 1.22 ± 0.15; α144→1400 ≈ 1.20 ± 0.10; consistent with aged synchrotron plasma.
    • Power at 144 MHz: ~2.27 × 10^26 W Hz−1.
  • Interpretation: a relic, re-energized shell—possibly by a powerful superwind or merger-driven shock; the twin-ring geometry suggests a bipolar, large-scale outflow acting on fossil lobes.

• Case B — A ring formed by diverted backflow (RAD J122622.6+640622)

  • Class: Giant Radio Galaxy with a ring at the end of a bent flow.
  • Redshift and environment: zspec = 0.11024 ± 0.00002; brightest cluster galaxy; cluster mass M500 ≃ 0.8 × 10^14 M⊙; R500 ≃ 590 kpc.
  • Scale and power: total size ≃ 865 kpc; ring diameter ≃ 100 kpc; P144 MHz ≈ 2 × 10^25 W Hz−1.
  • Morphology: inner jets look FR I–like; the north terminates in a hotspot (FR II–like), but the south jet bends sharply, forming a westward plume and a limb-brightened ring near the cluster’s virial boundary—likely a buoyant backflow vortex ring.
  • Why it matters: it shows rings can arise when jets are deflected by density gradients or obstacles, even without a full ORC shell.

• Case C — A ring at the end of a filamentary jet (RAD J142004.0+621715)

  • Class: Filamentary radio galaxy with a ring and complex cluster structures.
  • Redshift and environment: zspec = 0.14140 ± 0.00003; BCG in a massive cluster, M500 ≃ 1.63 × 10^14 M⊙, R500 ≃ 825 kpc.
  • Scale and power: total size ≃ 440 kpc; ring ≃ 64 × 47 kpc; P144 MHz ≃ 5.47 × 10^22 W Hz−1.
  • Interaction clues: a nearby edge-on disc galaxy sits on the ring’s western half; the ring looks compressed to the west with a tail to the east, as if pushed by motion or a wind. A C-shaped radio structure with no galaxy counterpart complicates the picture.
  • Hypothesis: possible jet–galaxy interaction or superwind deflecting radio plasma—akin to a bow shock on the “dayside” and a magnetotail downstream.

Here’s a compact, human-readable summary you can skim on a train.

Three radio rings found by RAD@home citizen scientists

Source	Type	Redshift	Ring size	Largest extent	Power at 144 MHz	Key clue
RAD J131346.9+500320	ORC (double ring)	zphot ≃ 0.937 ± 0.045	~300 kpc each	~800 kpc	2.27 × 1026 W Hz−1	Steep α ≈ 1.2; most distant and powerful ORC yet
RAD J122622.6+640622	GRG with ring	zspec = 0.11024	~100 kpc	~865 kpc	~2 × 1025 W Hz−1	Backflow diverted near R500 ≃ 590 kpc
RAD J142004.0+621715	Filamentary jet + ring	zspec = 0.14140	~64 × 47 kpc	~440 kpc	5.47 × 1022 W Hz−1	Possible jet–galaxy interaction; west-compressed ring

All values from the MNRAS study and related survey measurements.

An aha moment connects these three: rings are not a single phenomenon. They can be fossils jolted awake by superwinds. They can be vortex loops carved by diverted backflows. They can be the glowing footprint of a jet colliding with a galaxy’s gaseous halo. That diversity is the clue. Feedback comes in many shapes.

HTML math you can actually use To decode these radio fossils, astronomers lean on a few simple relations. First, the spectral index α, which tells us how fast the radio brightness falls with frequency:

$S\left(\nu \right)\propto {\nu }^{-\alpha }$

You can estimate α from two frequency measurements:

$\alpha =-\frac{\ln (S_2/S_1)}{\ln ({\nu }_2/{\nu }_1)}$

For the double-ring ORC, the measured flux densities at 54, 144, and 1400 MHz give α ≈ 1.2, consistent with aged, relic electrons rather than fresh jet hotspots.

And here’s a compact table of those fluxes.

Flux densities and derived spectral index for the double-ring ORC

Frequency	Survey	Flux density
54 MHz	LoLSS	143 ± 16 mJy
144 MHz	LoTSS	43.2 ± 4.1 mJy
1.4 GHz	NVSS	2.8 ± 0.6 mJy
Derived: α54→144 ≈ 1.22 ± 0.15; α144→1400 ≈ 1.20 ± 0.10

Data and α from the MNRAS analysis.

Why this all feels different—citizen scientists, pattern-finding, and the human eye Let’s say it plainly: machines miss weird stuff. The intersecting rings of the double-ring ORC were once auto-listed as an elongated double. A person—trained but curious—saw circles where the model saw lines. RAD@home is built for that moment. It’s a zero-funding, zero-infrastructure, all-heart collaboratory that trains volunteers to inspect multi-survey radio maps and escalate “non-standard” sources for professional follow-up. As datasets explode, this partnership matters: algorithms for speed and scale, humans for novelty and nuance. And in this discovery, citizen scientists directly helped surface the strongest, most distant ORC yet.

What might be powering these rings? We won’t pretend the story is finished. But the evidence points to a few mechanisms:

• Shock-revived fossil lobes. Old radio bubbles light up again when a large-scale shock passes through, often after a merger or black hole outburst. The steep spectra and shell-like geometry support this.

• Bipolar superwinds from the host galaxy. If a wind turns on after lobes fade, it can compress relic plasma into twin rings along opposite directions. That’s a clean way to make a double-ring ORC.

• Deflected jets and backflows. In clusters, jets get bent, backflows swirl, and rings can form where plasma rolls into vortex loops—especially near R500, where conditions change fast.

• Jet–galaxy encounters. A jet plowing into a dense galactic halo can create a bow-like, limb-brightened ring and a downstream tail—a cosmic echo of the solar wind vs. magnetosphere dance.

Search intent, satisfied If you searched “odd radio circles origin,” “double ring ORC,” “LoTSS ORC discovery,” “RAD@home citizen science,” “radio backflow vortex ring,” or “jet–galaxy interaction ring,” you’re here for mechanisms, measurements, and meaning. We’ve given you data (sizes, powers, redshifts), survey context (LoTSS, LoLSS, NVSS), formation scenarios (superwinds, shocks, backflows), and the human story (citizen science plus pro teams). These long-tail questions drive real curiosity; they also reflect the frontier.

Extra details for the curious mind

• Only about a dozen ORCs are known; double-ring cases are extremely rare.
• ORCs tend to show steep spectra, consistent with ageing synchrotron electrons.
• Many ORCs align with a plausible host galaxy; this one does, with a compact core showing a flat-spectrum signature at higher frequencies.
• Two more radio rings—one in a giant radio galaxy and one at the end of a filamentary jet—strengthen the black hole feedback connection but show environment matters.

Written for you, by us This article was written specifically for you by FreeAstroScience.com, where complex science gets human words. We believe you should never turn off your mind. Keep it sharp. Because the sleep of reason breeds monsters—and also, occasionally, mysterious rings.

Conclusion

We saw three rings. One is the most powerful ORC yet, double and distant, likely a revived fossil of past black hole weather. The second looks like a vortex loop born from a jet’s diverted backflow near a cluster’s edge. The third hints at a jet–galaxy encounter that sculpted a compact, limb-brightened arc. Different pathways, one theme: feedback shapes galaxies, and it leaves traces. As deeper, wider radio surveys roll in, expect more rings—and more puzzles. Bring your curiosity back to FreeAstroScience.com. We’ll keep translating the cosmos into stories you can feel—and facts you can trust.

The research has been published in the Monthly Notices of the Royal Astronomical Society.+