Okay, okay... They're not real Orcs, but they're just as odd...

Ray Norris and his team at Western Sydney University have discovered something unlike anything we've seen before.

"We have found an unexpected class of astronomical objects which have not previously been reported..."
"The objects appear in radio images as circular edge-brightened discs about one arcmin diameter, and do not seem to correspond to any known type of object."
"For brevity, and lacking an explanation for their origins, we dub these objects “Odd Radio Circles”, or ORCs."

^{Image Source: ATCA}

They observed three of these strange objects during the Pilot Survey of the Evolutionary Map of the Universe (EMU) using the Australian Square Kilometre Array Pathfinder (ASKAP), a radio telescope array spread across four kilometres of the outback. Upon first glance, the team thought they could just be dealing with a calibration error creating a glitch, but upon further study they learned one had been archived with the Giant MetreWave Radio Telescope (GMRT) all the way back in 2013 but had apparently gone unnoticed.

The nearly perfectly concentric rings of cosmic energy apparently have no "obvious optical, infrared, or X-ray counterparts to the diffuse emission..."

The aptly named objects appear to be made completely of radio waves, and are completely invisible to the naked eye, and they don't produce any heat or X-ray radiation. Though the circles themselves are invisible, the team does note that there is a galaxy near the center of two of the four ORCs observed. The team measured all four ORCs at around 1 "arcminute". While we'd need to know how far away they are to measure their size in lightyears, if we look at the image above and realize the little highlighted blob is a galaxy we can somewhat imagine just how massive these rings really are.

So what are ORCs?

The team proposes a number of possible explanations for the phenomena including ORCs being the leftovers of supernova explosions, face-on ring galaxies, and so called Einstein Rings, among other hypotheses. Though planetary nebulae can often appear as diffuse radio emmissions, Norris and his team explain that it's unlikely ORCs could be PNe simply due to their rarity. To find so many ORCs within their limited observation area would be like winning the lottery, so Occam's Razor pretty much rules that option out.

While more research is required to determine exactly what's producing these awe inspiring demonstrations of the universe, scientists are definitely having fun with the idea of ORCs invading the stars...

Sources:

• https://arxiv.org/abs/2006.14805
• https://www.livescience.com/circular-radio-objects-space.html
• https://www.sciencealert.com/mysterious-unidentified-circles-have-been-found-in-space

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