Odd radio circles in space may come from black holes at their centres

By Leah Crane.

One of the strangest phenomena in space has a sharper image. The odd radio circles, or ORCs, are circles of radio waves that don't emit any radiation in the other wavelength.

The strange circles were first spotted by a team of researchers led by Ray Norris. Astronomers have spotted five of them. They used the telescope in South Africa to take the best image yet of an ORC.

Odd radio circles are larger than the largest spiral galaxies. Astronomers have seen three of the five confirmed ORCs and it is possible that the circles are the result of a process in the universe.

Read more: Something strange is sending radio waves from the centre of the galaxy

All ORCs seem to have central galaxies with active black holes. The options for what ORCs could be narrowed down by that. They could be debris from a huge explosion in their host galaxies, they could come from jets of material flung out by supermassive black holes, or they could be residual energy from bursts of star formation.

It will take more observations with more sensitive radio telescopes to figure out which of these explanations is correct. The Square Kilometre Array, a huge array of radio telescopes with sections in both Australia and South Africa, is expected to find many more ORCs and help close the book on what they really are.

Monthly Notices of the Royal Astronomical Society is a journal reference.

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