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Research team examines galactic phenomena called Odd Radio Circles

ORC1 is an Odd Radio Circle, captured by a MeerKAT radio telescope in South Africa.
Jayanne English
University of Manitoba
ORC1 is an Odd Radio Circle, captured by a MeerKAT radio telescope in South Africa.

They’re balls of gas, and they’re called ORCs. The acronym stands for Odd Radio Circles, where "radio" refers to their wavelength of light.

They were first seen in 2019, and now a research team led by UC San Diego has sought to explain the clouds of gas surrounding galaxies. To call them huge is, if anything, a great understatement.

“They are enormous. They are a scale much larger than a galaxy and basically a physical scale that we don’t see anything else like this in the universe,” said Alison Coil, a professor of astrophysics at UC San Diego.


ORCs are hundreds of thousands of light years in diameter, typically with a galaxy in the center of them.

Coil’s research team believes shockwaves from multiple exploding stars created a wind that pushed the gas we see into space, making a cloud with an ever-expanding radius.

“It’s from gas that we think exploded out of the galaxy a long time ago, hundreds of millions of years ago, that’s been expanding out into intergalactic space, the region in between galaxies,” Coil said.

Star creation goes hand in hand with star destruction. Coil said the winds that created ORCs were not from just one supernova but several exploding stars, something that often happens when galaxies collide.

She spoke about ORC4, one she observed from the Keck Observatory in Hawaii.


“So we think that this galaxy had a starburst event that led to these multiple supernovae, kind of building on each other, and then it drove gas out of this galaxy at a really high speed and a really high rate,” she said.

She said 11 ORCs had been discovered so far.

Coil said that space is a much more dynamic place than some people imagine. It’s filled with moving objects and winds that stir up gasses. And the discovery of the Odd Radio Circles is another example of that.

“It’s pretty rare to discover a new class of extragalactic objects,” she said. “But we’re still encountering new mysteries because of all the new data we’re getting.”

And, speaking of galaxies colliding, you may have heard our Milky Way galaxy is on a collision course with the Andromeda galaxy. Coil said it was something we wouldn’t have to worry about anytime soon.