In September 2019, my colleague Anna Kapinska gave a presentation showing the interesting objects she had found while looking at our new radio astronomy data. She had begun to notice many strange shapes that could not easily fit into any known type of object.
Among them, designated by Anna as WTF?, was a picture of a ghostly circle of radio radiation hanging in space like a cosmic smoke ring.
None of us had ever seen anything like it before, and we had no idea what it was. A few days later, our colleague Emil Lenz found a second, even more ghostly than Anna’s.
Anna and Emil explored the new images from our pilot observations for the Evolution Map of the Universe (EMU) project, made with CSIRO̵
EMU plans to boldly explore parts of the universe where no telescope has ever traveled. This can happen because ASKAP can very quickly explore large parts of the sky, exploring depths previously reached only in small areas of the sky, and is particularly sensitive to weak, diffuse objects like these.
I predicted that a few years ago, this study of the unknown would probably make unexpected discoveries, which I called the WTF. But none of us expected to find something so unexpected, so fast.
Due to the huge amount of data, I expected the discoveries to be made with the help of machine learning. But these discoveries were made with a good old-fashioned eye.
Our team searched the rest of the data and found several more of the mysterious round spots. We called them ORC, which means “weird radio circles.”
But the big question, of course, is, “What are they?”
We initially suspected an image artifact, possibly generated by a software bug. But we soon confirmed that they are real, using other radio telescopes. We still have no idea how big or far they are.
They could be objects in our galaxy, maybe a few light-years in diameter, or they could be far away in the universe, and maybe millions of light-years.
When we look at images taken with optical telescopes in the ORC position, we see nothing. The rings of radio emission are probably caused by clouds of electrons, but why don’t we see anything in the 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 ruled out several possibilities for what the ORC could be.
Could they be the remnants of a supernova, the clouds of debris left behind by the explosion of a star in our galaxy? No. They are far from most of the stars in the Milky Way and there are too many of them.
Could they be the rings of radio emission sometimes observed in galaxies subjected to intense starbursts? Again, no. We don’t see a single major galaxy hosting the star formation.
Could they be the giant lobes of radio emission we see in radio galaxies caused by jets of electrons sucking out of the vicinity of a supermassive black hole? Not likely because ORCs are very distinctly round, unlike the tangled clouds we see in radio galaxies.
Could they be Einstein’s rings in which the radio waves from a distant galaxy are bent in a circle by the gravitational field of a cluster of galaxies? Not yet. ORCs are too symmetric and we do not see a cluster in their center.
A real mystery
In our forthcoming article on ORC Publications of the Astronomical Society of Australia, we look at all the possibilities and conclude that these mysterious spots do not look like something we already know.
So we need to study things that may exist but have not yet been observed, such as a huge shock wave from an explosion in a distant galaxy. Such explosions may have something to do with rapid radio bursts or collisions of a neutron star and a black hole 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.
From the handful we’ve found so far, we estimate there are about 1,000 ORCs in the sky. My colleague Bärbel Koribalski notes that there is already a demand for telescopes around the world to find more ORCs and to understand their cause.
This is a difficult job because ORCs are very weak and difficult to find. Our team thinks about all these ideas and more, hoping for the moment of eureka, when one of us, or maybe someone else, suddenly gets a flash of inspiration that solves the puzzle.
This is an exciting time for us. Most astronomical research is aimed at improving our knowledge of the universe or testing theories. Very rarely do we face the challenge of encountering a new type of object that no one has seen before and trying to understand what it is.
Is it a completely new phenomenon or something we already know about but look at in a strange way? And if it is really completely new, how does it change our understanding of the universe? Watch this space!
Ray Norris, Professor, School of Science, West Sydney University.
This article is republished by The Conversation under a Creative Commons license. Read the original article.