Australia’s square kilometer matrix pathfinder was used to scan the skies for radio waves. (Credit: CSIRO)
There’s something unusual lurking deep in space: Astronomers have discovered four faint objects that are highly circular and brighter along the edges at radio wavelengths. And they are unlike any kind of astronomical object ever seen before.
The objects, which look like distant islands in the shape of a ring, have been called strange radio circles or ORCs, due to their shape and general peculiarity. Astronomers don’t yet know exactly how far away these ORCs are, but they could be linked to distant galaxies. All of the objects were found far from the Milky Way’s galactic plane and are about 1 arc minute in diameter (the moon’s diameter is 31 arc minutes in comparison).
In a new document detailing the discovery, astronomers offer several possible explanations, but none meet the requirements for the four new ORCs. After ruling out objects like supernovae, star-forming galaxies, planetary nebulae, and gravitational lenses, a magnifying effect due to the flexion of space-time by nearby massive objects, among other things, astronomers speculate that the objects could be shock waves. of some extragalactic event or possibly radiogalactic activity.
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“[The objects] it could well point to a new phenomenon that we haven’t really investigated yet, “said Kristine Spekkens, an astronomer at the Royal Military College of Canada and Queen’s University, who was not involved in the new study.” It may also be an extension of a previously known class of objects that we were unable to explore. “
Spekkens added that objects could also be caused by different phenomena. All four ORCs are bright at radio wavelengths but invisible in visible, infrared, and X-ray light. But two of the ORCs have galaxies at their center that can be seen at visible wavelengths, suggesting that these objects could having been formed by those galaxies. Two ORCs also appear to be very close together, meaning that their origins could be linked.
Astronomers detected three of the objects while mapping the night sky at radio frequencies, part of a pilot survey for a new project called the Evolutionary Map of the Universe (EMU). The EMU pilot used Australia’s Square Kilometer Array Pathfinder, or ASKAP, from July to November 2019. This radio telescope array uses 36 dish antennas, which work together to observe a wide-angle view of the night sky. They found the fourth ORC in archival data collected by the Giant MetreWave radio telescope in India. This helped astronomers confirm the objects as real, rather than some anomaly caused by problems with the ASKAP telescope or the way the data was analyzed.
With only four of these peculiar objects discovered so far, astronomers still can’t figure out the true nature of these structures. But the EMU survey is just beginning, and astronomers hope it will reveal more unusual objects.
By combining the ability to see faint radio objects with a wide gaze, the survey is in a unique position to find new objects. EMU scientists have predicted that the project will find around 70 million new radio objects, expanding the current catalog by about 2.5 million.
“This is a very good indication of the shape of what will come in radio astronomy in the coming years,” Spekkens told Live Science. “History shows us that when we open a new [avenue of looking at] space to explore … we always find new and exciting things. “
The document, which is available on the arXiv prepress site, has been submitted for publication to the journal Nature Astronomy, where it is still under review.
Originally published in Live Science.
