update: March 2022:
- Phis.org: Astronomers reveal best image yet of mysterious odd radio circles in space
- Science Alert: Weird Circular Objects Observed in Space May Finally Be Explained
- MNRAS: Mysterious odd radio circle near the large magellanic cloud – an intergalactic supernova remnant?
The Conversation's ‘Dancing ghosts’: a new, deeper scan of the sky throws up surprises for astronomers says:
We are getting used to surprises as we scan the skies in the Evolutionary Map of the Universe (EMU) project, using CSIRO’s new Australian Square Kilometre Array Pathfinder (ASKAP), a radio telescope that probes deeper into the Universe than any other. When you boldly go where no telescope has gone before, you are likely to make new discoveries.
A deep search returns many surprises
The Dancing Ghosts were just one of several surprises found in our first deep search of the sky using ASKAP. This search, called the EMU Pilot Survey, is described in detail in a paper soon to appear in the Publications of the Astronomical Society of Australia.
The first big surprise from the EMU Pilot Survey was the discovery of mysterious Odd Radio Circles (ORCs), which seem to be giant rings of radio emission, nearly a million light years across, surrounding distant galaxies.
It includes the image below, which shows radio emission in "retro bluegreen" as a fuzzy blob floating in front of distant stars and galaxies.
Two things caught my eye:
- I've seen this object in several original Star Trek episodes I'm sure!
- Represented this way it's transparent. You can see stars and galaxies right through it.
Question: What's known about Odd Radio Circle appearance? What would they really look like if we could see them? Are they transparent/translucent in radio, or opaque?
The first ‘Odd Radio Circle’. Radio data are green and the white and coloured data show the optical background from the Dark Energy Survey. image created by Jayanne English from data from EMU and the Dark Energy Survey (Creative Commons licence)