There is something unusual that lurks in the depths of space: Astronomers have discovered four faint objects that, at radio wavelengths, are very circular and lighter along their edges. And they are unlike any class of astronomical objects ever seen before.
The objects, which look like distant annular islands, have been called odd radio circles, or ORCs for their shape and overall peculiarity. Astronomers do not yet know exactly how far these ORCs are, but they can be connected to distant galaxies. All objects were found away from Milky Way̵
In a new article describing the discovery, astronomers offer several possible explanations, but none really fits the bill for all four new ORCs. After excluding objects such as supernovae, star-forming galaxies, planetary nebulae and gravitational lenses – a magnifying effect due to dwelling in the space of nearby massive objects – astronomers speculate, among other things, that the objects may be shockwaves from some extra-galactic event or possibly activity radio galaxy.
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“[The objects] may very well point to a new phenomenon that we haven’t really investigated yet, “said Kristine Spekkens, astronomer at the Royal Military College of Canada and Queen’s University, who was not involved in the new study.” It may also be that these are an extension of a previously known class of objects that we have not been able to explore. “
Speckens added that the objects can also be caused by different phenomena. All four ORCs are bright at radio wavelengths but invisible in visible, infrared light and X-rays. However, two of the ORCs have galaxies in the center that can be seen with visible wavelengths, suggesting that these objects may have been formed by these galaxies. Two ORCs also appear to be very close to one another, which means their origin can be linked.
Astronomers discovered three of the objects while mapping the night sky in radio frequencies, part of a pilot study for a new project called the Evolutionary Map of the Universe (EMU). The EMU pilot used the Australian Square Kilometer Array Pathfinder, or ASKAP, from July to November 2019. This radio telescope set uses 36 dish antennas, which work together to observe a wide-angle view of the night sky. They found the fourth ORC in archive data collected by Giant MetreWave Radio Telescope in India. This helped astronomers to confirm the objects as real, rather than an anomaly caused by problems with the ASKAP telescope or the way the data was analyzed.
With only four of these strange objects discovered so far, astronomers cannot yet tease out the true nature of these structures. But the EMU survey is just beginning and astronomers expect it to reveal more unusual objects.
By combining an ability to see weak radio objects with a broad look, the survey is uniquely positioned to find new objects. EMU researchers have predicted that the project will find about 70 million new radio objects – and expand the current catalog by about 2.5 million.
“This is a really nice indication of the shape of things that will come in radio astronomy over the next few years,” Spekkens told Live Science. “History shows us that when we open up a new one [avenue of looking at] space to explore … we always find new and exciting things. “
The thesis, which is available on the reprint page arXiv, has been submitted for publication in the journal Nature Astronomy, where it is still under review.
Originally published on Live Science.