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OPINION: In September 2019, my colleague Anna Kapinska gave a presentation showing interesting objects that she had found while browsing our new radio astronomical data. He had begun to notice very strange shapes that he could not easily fit into any known type of object.
Among them, labeled by Anna as WTF?, was an image of a ghostly circle of radio emission, hanging in space like a cosmic smoke ring. Neither of us had seen anything like this before, and we had no idea what it was. A few days later, our colleague Emil Lenc found a second, even scarier than Anna’s.
Anna and Emil had been examining the new images from our pilot observations for the Evolutionary Map of the Universe (EMU) project, made with CSIRO’s revolutionary new Australian Square Kilometer Array Pathfinder (ASKAP) telescope.
EMU plans to boldly probe parts of the Universe where no telescope has gone before. It can do this because ASKAP can scan large swaths of the sky very quickly, probing at a depth previously only reached in tiny areas of the sky, and is especially sensitive to faint and fuzzy objects like these.
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A couple of years ago I predicted that this exploration of the unknown would likely make unexpected discoveries, which I called WTF. But none of us expected to discover something so unexpected, so fast. Due to the huge volumes of data, I expected the discoveries to be made using machine learning. But these discoveries were made with a good old-fashioned look.
Image by Bärbel Koribalski based on ASKAP data, with optical image from Dark Energy Survey
The ghostly ORC1 (blue / green fuzz), on a background of galaxies at optical wavelengths. There is an orange galaxy in the center of the ORC, but we don’t know if it’s part of the ORC or just a chance coincidence.
ORC hunting
Our team searched the rest of the data by eye and found a few more of the mysterious round spots. We call them ORC, which stands for “strange radius circles.” But the big question, of course, is: “what are they?”
At first we suspected an image artifact, perhaps generated by a software bug. But we soon confirm that they are real, using other radio telescopes. We still have no idea how big or far away they are. They could be objects in our galaxy, perhaps a few light years across, or they could be very far away in the Universe and perhaps millions of light years across.
When we look at images taken with optical telescopes at the position of the ORCs, we don’t see anything. The radio emission rings are probably caused by electron clouds, but why don’t we see anything at visible wavelengths of light? We don’t know, but finding a puzzle like this is every astronomer’s dream.
We know what they are not
We have ruled out several possibilities of what ORCs could be.
Could they be supernova remnants, the debris clouds that remain when a star explodes in our galaxy? No. They are far from most of the stars in the Milky Way and there are too many.
Could it be the radio emission rings that are sometimes seen in galaxies that experience intense bursts of star formation? Not again. We do not see any underlying galaxy that hosts the star formation.
Could it be the giant lobes of radio emission we see in radio galaxies, caused by jets of electrons spurting out from the surroundings of a supermassive black hole? Not likely, because ORCs are clearly circular, unlike the tangled clouds we see in radio galaxies.
Could they be Einstein rings, in which the gravitational field of a galaxy cluster bends radio waves from a distant galaxy in a circle? Not yet. The ORCs are too symmetrical and we don’t see a cluster at their center.
A real mystery
In our article on ORC, which will be published soon in the Publications of the Astronomical Society of Australia, we reviewed all the possibilities and concluded that these enigmatic spots are not like anything we already know.
So we need to explore things that might exist but have not yet been observed, such as a large shock wave from some explosion in a distant galaxy. Such explosions may have something to do with fast radio bursts, or the collisions of neutron stars and black holes that generate gravitational waves.
Or maybe they are something else entirely. Two Russian scientists have even suggested that ORCs could be the “throats” of wormholes in space-time.
Of the few we have found so far, we estimate that there are around 1000 ORCs in the sky. My colleague Bärbel Koribalski points out that the search is on, with telescopes all over the world, to find more ORCs and understand their cause.
It is a complicated job, because the ORCS are very weak and difficult to find. Our team is brainstorming all these ideas and more, waiting for the eureka moment when one of us, or maybe someone else, suddenly has the flash of inspiration that solves the puzzle.
It is an exciting time for us. Most astronomical research aims to refine our knowledge of the Universe or to test theories. Very rarely are we faced with the challenge of stumbling across a new type of object that no one has seen before and trying to figure out what it is.
Is it a completely new phenomenon or something we already know but seen in a strange way? And if it really is completely new, how does that change our understanding of the Universe? Look at this space!
Ray Norris is a professor at the Western Sydney University School of Science.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
