In the last few decades, astronomers have seen a handful of gigantic and almost perfectly circular radio objects out in the distant universe. Though no one has an explanation for all these mysterious entities yet, a team has recently added another one to their catalog, potentially moving them closer to solving this head-scratcher.
The enigma began shortly after the Australian Square Kilometre Array Pathﬁnder (ASKAP), a bank of 36 colossal dishes in Western Australia that scans the skies in the radio section of the electromagnetic spectrum, started producing maps of the entire night sky in 2019.
ASKAP scientists were mainly looking for smart resources that could indicate the presence of black holes or enormous galaxies shining in radio waves. But some in the team are constantly on the search” for whatever is weird, whatever is new, and whatever resembles nothing else,” Bärbel Koribalski, a galactic astronomer in Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Western Sydney University in Australia, advised Live Science.
From the statistics, team member Anna D. Kapińska of the National Radio Astronomy Observatory in Socorro, New Mexico, seen four glowing radio circles, Koribalski recalled, though originally the rest of the researchers dismissed them as a more familiar occurrence.
Nevertheless, if telescopes tried to examine the items in other wavelengths, like the optical light our eyes use to see, they turned up empty, causing the team to dub them odd radio circles (ORCs).
Even stranger, every one of the ORCs needed a galaxy perched nearly exactly in its center, like a bullseye. The astronomers could determine that the entities were every several billion light-years off and potentially as large as a few million light-years in diameter.
Nobody had seen anything like those before, and in a paper published this past year, the group offered 11 potential explanations as to what they could be, such as imaging glitches, warps in space-time known as Einstein rings, or a new sort of remnant out of a supernova explosion.
The researchers have watched the skies again with ASKAP and discovered yet another ORC to add to their collection, a thing about 1 million light-years across located approximately 3 billion light-years away.
The group has now narrowed down their ideas to three potential explanations, Koribalski explained. The first is that maybe you will find additional galaxies forming a bunch close to the item and bending bright substance to a ring-like construction. These might simply be too feeble to be picked up by current telescopes.
Another possibility is that the central supermassive black hole of these galaxies is consuming dust and gas, producing humongous, cone-shaped jets of particles and energy. Astronomers have regularly spotted such phenomena in the world, though generally, the jets align in this way with Earth that observatories see them as moving out of the sides of the galaxy.
Maybe in the case of the ORCs, the jets are simply pointing directly towards our world, Koribalski suggested, so that we are in essence looking down the barrel of a long tube, creating around, the two-dimensional image around a central galaxy.
“The other explanation is more exciting,” she said. “This may be something completely new.”
It’s possible that some unknown but highly energetic event took place in the center of these galaxies, creating a burst wave that traveled out as a world and caused a ring structure. Kowalski isn’t yet certain what sort of event could leave such a signature, though perhaps it is a previously unknown product of crashing black holes such as the type seen in gravitational waves at the Big Interferometer Gravitational-Wave Observatory (LIGO) in America.
But Harish Vedantham, an astronomer at the Netherlands Institute for Radio Astronomy who wasn’t linked to the work, favors the simpler idea — which the ORCs are a reflection of a phenomenon that is well-known, and so are bright jets shooting from a galaxy in a seldom seen angle.
Vedantham is advised in this by the principle of Occam’s razor, which favors ordinary explanations over strange, new ones. “You can construct an exotic situation,” he advised Live Science. “However, the simplest answer is nearly always correct.”
In a similar vein, the possibility that an ORC is an imperceptible galactic cluster is not appealing to him because”it’s kind of hard to conceal a cluster,” he explained. The objects are far off, but they are not that much, so at least a few additional galaxies should be evident, he added.
Two Vedantham and Koribalski concur that more telescope observations in different wavelengths should help scientists get a better idea of what is going on. New data will be forthcoming in the next six months or so, hopefully adding added ORCs for their catalog, Koribalski said.
Meanwhile, she’s somewhat enjoying the mystery. “You become a detective. You look at each of the clues and weigh them up against each other,” she said. “Sometimes the world just comes up with weird and wonderful shapes.”