There's something unusual lurking out in the depths of space: Astronomers have discovered four faint objects that at radio wavelengths are highly circular and brighter along their edges.
The objects, which look like distant ring-shaped islands, have been dubbed odd radio circles, or ORCs, for their shape and overall peculiarity.
After ruling out objects like supernovas, star-forming galaxies, planetary nebulas and gravitational lensing — a magnifying effect due to the bending of space-time by nearby massive objects — among other things, the astronomers speculate that the objects could be shockwaves leftover from some extragalactic event or possibly activity from a radio galaxy.
Related: The 12 strangest objects in the universe.
But two of the ORCs have galaxies at their center that can be seen at visible wavelengths, which suggests that these objects might have been formed by those galaxies.
Astronomers spotted three of the objects while mapping the night sky in radio frequencies, part of a pilot survey for a new project called the Evolutionary Map of the Universe (EMU).
This helped the astronomers to confirm the objects as real, rather than some anomaly caused by issues with the ASKAP telescope or the way in which the data was analyzed.
With only four of these peculiar objects discovered so far, the astronomers can't yet tease out the true nature of these structures.
By combining an ability to see faint radio objects with a wide gaze, the survey is uniquely positioned to find new objects.
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