In 2019, my colleagues and I discovered spooky glowing rings in the sky using CSIRO’s ASKAP radio telescope in Western Australia. The rings were unlike anything seen before, and we had no idea what they were.
We dubbed them odd radio circles or ORCs. They continue to puzzle us, but new data from South Africa’s MeerKAT telescope are helping us solve the mystery.
We can now see each ORC is centered on a galaxy too faint to be detected earlier. The circles are most likely enormous explosions of hot gas, about a million light-years across, emanating from the central galaxy.
Our paper showing these results has been peer-reviewed and accepted for publication by Monthly Notices of the Royal Astronomical Society.
A closer look
We now have beautiful images of one of these rings taken with South Africa’s MeerKAT radio telescope, which shows the ORC in stunning detail.
For example, MeerKAT sees a small blob of radio emission in the center of the ring, which is coincident with a distant galaxy. We are now fairly certain this galaxy generated the ORC.
We see these central galaxies in other ORCs too, all at vast distances from Earth. We now think that these rings surround distant galaxies about a billion light-years away, which means the rings are enormous – around a million light-years across.
From modeling the faint cloudy radio emission that MeerKAT detects within the rings, it seems the rings are the edges of a spherical shell surrounding the galaxy, like a blast wave from a giant explosion in the galaxy. They look like rings instead of orbs only because the sphere appears brighter at the edges where there is more material along the line of sight, much like a soap bubble.