We discovered glowing rings in the sky using a radio telescope. We had no idea what the rings were.
We called them odd radio circles. New data from the South Africa's MeerKAT telescope is helping us solve the mystery.
We can see that the ORC is centered on a faint galaxy. The circles are made of hot gas, which is about a million light years across.
The paper showing these results has been peer reviewed and accepted for publication.
The ORC is shown in stunning detail in the images of one of these rings taken with South Africa's MeerKAT radio telescope.
The Dark Energy Survey was conducted by Jayanne English.
The image of the odd radio circle ORC1 is superimposed on an optical image from the Dark Energy Survey.
There is a small blob of radio emission in the centre of the ring, which is near a distant galaxy. We are pretty sure that the ORC was generated by this galaxy.
We can see the central galaxies in other ORCs. The rings are around a million light-years away, which means they surround a billion light-years away.
It seems that the rings are the edges of a spherical shell, like a blast wave from a giant explosion, because of the faint cloudy radio emission that MeerKAT finds.
The sphere appears brighter at the edges where there is more material along the line of sight, like a soap bubble.
An artist's impression of radio circles exploding from a central galaxy. It is thought that it will take 1 billion years for the rings to reach their current size. The rings are so large that they have expanded past other galaxies. Sam Moorfield is from the CSIRO.
The magnetic field in the ring is shown by the map of the radio waves. A magnetic field runs along the edge of the sphere.
This suggests that an explosion in the central galaxy caused a hot blast outside. The electrons in the gas were made to spiral around the magnetic field by the shock wave.
The data is from Larry Rudnick and MeerKAT.
The direction of the magnetic field can be seen in the lines around the ORC. A circular magnetic field is indicative of a shock wave from the central galaxy.
There are several curved filaments of radio emission within the ring. We don't know what they are.
We know that the sphere has swallowed up other galaxies as it blasted out from the central galaxy. The gas may have been ripped off the galaxies by the passing shock wave.
What caused the explosion is the big question. We are looking at two possibilities.
They were caused by the merging of two black holes. Amerger event releases an enormous amount of energy, enough to generate the ORC.
There is a chance that the central galaxy went through a large event in which millions of stars were born. A spherical shock wave can be caused by a hot gas blast from the galaxy.
Black hole mergers and starburst events are rare, which is why ORCs are so rare.
The puzzle of ORCs is not solved yet, and we still have a lot to learn about the mysterious rings in the sky. We have only seen nothing from the rings at optical, X-ray, or IR wavelengths, so far.
To find out more, we need a tool that is even more sensitive. An observatory with telescopes in South Africa and Australia is being built by the global astronomy community.
The sites were built to test the technology. Major discoveries have been made in the first year of operation of both telescopes, apart from their role as precursors for the SKA.
Their success in discovering and studying ORCs bode well for the SKA.
The two telescopes are both excellent at surveying large areas of sky and finding new objects, while the other is better at zooming in on those objects and studying them with higher sensitivity and resolution.
The SKA will surpass both of them. Many more ORCs will be found by the SKA, and will be able to be probed to find out what they are telling us about the life cycle of galaxies.
The School of Science at Western Sydney University has a professor named Ray Norris.
This article is free to use under a Creative Commons license. The original article is worth a read.
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