Chapter 1: What mysterious signals have we detected from deep space?
WTF. That's what radio astronomer Anna Kopinska labelled the image of an enormous, mysterious blob she first spotted in 2019. Billions of years from Earth, in the realms of deep space, it appeared like a ghostly ring of smoke. A glowing oddity of radio waves that didn't appear to match up with any known supernova remnant or galactic interaction. What in the world, in the universe, could this be?
It may have been unusual, but this object was not alone. Named Odd Radio Circles, or AUX, the objects we have found seem to encompass everything we struggle to explain in the cosmos. 5 orcs have been confirmed since Kopinska's first finding, and several more blobs may fit the profile.
What cosmic force is so powerful that it could sculpt a ring of energy a million light years wide, so vast it dwarfs our Milky Way by a factor of ten? Are these radio rings the relics of galactic rebirth, or the dying echoes of something we have yet to comprehend? And why haven't we found more of them? I'm Alex McColgan, and you're watching Astrum.
Join me today as we attempt to unravel one of modern astronomy's greatest mysteries, and reveal the four leading hypotheses that could unlock the origin of these objects so odd they defy even the universe's standards. This mystery first began as a result of modern technology.
Around the turn of the new millennium, technological advancements in radio astronomy drastically increased the number of known radio sources from just a few hundred thousand to a couple million.
For decades, nobody was able to significantly increase that number.
That is, until recently. Radio astronomy was due for another upgrade, and Australia's National Science Agency, the Commonwealth Scientific and Industrial Research Organisation, oversaw the launch of the revolutionary Australian Square Kilometre Array Pathfinder Telescope, or ASCAP. one of several new radio telescopes coming online at the time.
With 36 radio dishes that are each 12 metres across, what makes the Western Australia Radio Telescope special is its phased array feed, which allows it to image huge areas of the sky at once. unlike the previous generation of radio telescopes. ASCAP's field of view is an impressive 30 square degrees, the equivalent to the surface area of about 150 moons as seen from Earth.
The phased array feed allows astronomers to ignore radio signals from things like satellites, which can otherwise create blind spots for radio telescope receivers. With this new generation of telescopes, radio astronomers are able to detect even faint, diffuse objects.
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Chapter 2: What are Odd Radio Circles and how were they discovered?
After all, the name odd radio circles is meant as a descriptive name, like an umbrella term for any odd radio circle that can't be described by any existing type of object.
So while all Orcs may include odd radio circles, each individual Orc may have its own unique origin story.
The discovery of Orc 2 and 3, the second and third odd radio circles to be identified, didn't do much to help solve the mystery of how Orcs are created. In fact, they introduced even more questions. Seen in this greyscale image, the two Orcs appear to be very close to each other, nearly touching.
They are roughly the same size, but on the right side of the image, Orc 2 is bright and clearly ring-shaped, while Orc 3, located to the left, is faint and appears more like a disc. In fact, Orc 3 may not even be recognisable in the greyscale emu image, if it weren't for the light grey speckles seeming to cluster together into a circular shape right next to the more distinct ring shape of Ork II.
Now take a look at this colour image of Ork II and Ork III. The diffuse radio emission has been enhanced in red and overlaid on top of the original radio pattern in green. You can see the obscured green colour behind the red glow, where the ring shape of Orc 2 is located, and to the left you can see its fainter sister circle of Orc 3, only visible in diffuse red.
The proximity of these Orcs would suggest that they are related somehow, but if that's the case, why do they appear so different?
As much as I'd like to tell you that we've solved this curious case of Ork 2 and Ork 3 since their discovery, which was published in 2021, the nature of these sister Orks remains an unsolved mystery to this day. Before moving on to the theories for Ork 4's origin, I've got to mention Ork 5, which was discovered in Australian Square Kilometre Array Pathfinder data in 2021.
While we don't have any leading theories for Orc 5 specifically, this Orc was found to have a central elliptical galaxy, like Orcs 1 and 4. And interestingly, Orc 5 was the only one found to have both this central galaxy and a nearby neighbouring galaxy found at approximately the same distance from the Orc ring, which suggests these two galaxies are likely interacting gravitationally.
While there may be some repeating characteristics, for every orc we've confirmed so far, it seems that each one has their own unique qualities. Of course, as we discover and confirm more orcs, it may be that this won't be the case in the future. But with so few orcs and so little observational evidence, it's been difficult for scientists to nail down one theory for their origin.
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Chapter 3: What technological advancements have improved our understanding of radio astronomy?
But even though the jury is still out on how AUX came to be, we are constantly gaining new insights from the likes of Project EMU and ASCAP. While studying EMU data from a nearby dwarf galaxy called the Small Magellanic Cloud, astronomers spotted the ghostly remains of two supernova remnants that were previously unknown to science, adding to our catalogue of celestial objects.
In addition to those, another nearby supernova remnant was found by using the EMU survey in 2023, and turned out to be one of the closest supernova remnants to our Earth, at just 4,200 light years away. This supernova remnant, known as this, was found to be about 130 light years across, and is thought to be just 13,000 years old.
Not only has EMU aided in the discovery of previously unknown supernova remains, it is also paving the way for using machine learning and the power of citizen science to identify and catalogue some 4 million radio sources, which could include orcs, as part of a project called the Radio Galaxy Zoo, EMU, or RGZ-EMU.
As of 2025, the project has had more than 2,000 volunteers and has helped to classify more than 92,000 sources. But the coolest part? You can join in and be part of the citizen science project yourself. To learn more, visit zooniverse.org and search for the Radio Galaxy Zoo EMU project.
As our tools continue to improve, I believe that astronomers are bound to discover more orcs, and even more objects we don't know even exist yet. We may learn not just how these radio rings formed, but we could also learn more about the life cycles of galaxies, the effects of starburst events, and how we may be able to trace gas from ancient events far outside their galaxy of origin.
For now though, the mystery of the origin of these odd radio circles persists, although with several promising hypotheses. And to unravel this mystery, astronomers will have to conduct cosmic archaeology on a scale almost too big to fathom. In 2022, astronomers using the Murchison Wide Field Array discovered a strange new radio signal that was arriving every 22 minutes.
The astronomers were no strangers to such repeating signals. They typically come from pulsars, neutron stars which send intense pulses of light across the universe as they rotate on their axis.
But as they began to look deeper into records of past observations, they realised this signal had been arriving at Earth since at least 1988, with remarkable stability, far more stable than is expected for a pulsar rotating every 22 minutes. If it was a neutron star, it was unlike any they had seen before. So, where was this signal coming from? I'm Alex McColgan, and you're watching Astrum.
Join me today as we grapple with the mystery that lies behind this signal, which will challenge our understanding of some of the most awe-inspiring objects in our cosmos. The location of the source, named GPM J1839-10, is roughly 18,000 light years away. Its signal arrives as pulses that can last any amount of time between 30 seconds and 5 minutes.
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Chapter 4: What are the leading hypotheses regarding the origin of Odd Radio Circles?
If we could see it all with the naked eye, Gaminga's gamma ray glow would dominate our sky, covering an area 40 times bigger than the full moon. With this new information, astrophysicists found that the size of Gominga's halo meant that this one pulsar alone could be responsible for as much as 20% of the excess positrons detected near Earth.
From there, it's no stretch to imagine that other pulsars are the most likely culprit for the remaining antimatter abundance we found. This explanation may not have solved the mystery of dark matter, but it is certainly a magnificent revelation.
It was Jocelyn Bell Bunnell who discovered the first pulsar in 1967, back when people thought that those regular signals could be the work of extraterrestrial life. In the nearly 60 years that have passed since, we have found thousands of pulsars, and our understanding of these neutron stars has grown with every one.
And since Gominga was identified as only the third known gamma ray pulsar in 1991, we've now spotted over 300, thanks to NASA's Fermi mission. But given Gominga's track record of defying expectations and furthering science, I like to think that this particular pulsar has more secrets still to reveal.
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