Astronomers have captured a close-up image of a rare and mysterious space object, giving it a new lease on life. Odd Radio Circles (ORCs) are huge curves of radio waves. Only five have been seen so far and never in such spectacular detail.
The image of the ORC J2103-6200, also called ORC1, was captured by a high-resolution MeerKAT radio telescope in South Africa, which gave researchers unprecedented information about these rare phenomena. Details are reported in a preprint posted on arXiv1 this week and will be published in the Royal Astronomical Society 2’s monthly notice.
“This discovery will lead to new scientific research among astronomers,” said Alice Passeto, a radio astronomer at the National Autonomous University of Mexico in Mexico City.
New MeerKAT radio data show that the ORC’s large outer circle is possibly more than a million light-years, tens of times the diameter of the Milky Way, with a series of small rings inside. “It really reminds me of a Faberge egg or a soap bubble,” says Barbel Koribalski, a radio astronomer at the Commonwealth Scientific and Industrial Research Organization in Sydney, Australia.
The first three ORCs with ORC1 were discovered in 2019 using the Australian Square Kilometer Array Pathfinder (ASKAP) telescope. The fourth was discovered in 2013 in data stored in India’s Giant Meterwave Radio Telescope, and the fifth was discovered by Koribalski in the new ASKAP. Data last year 3. Most ORCs have a galaxy at their center, which astronomers suggest may have something to do with their formation. Scientists are also surprised that ORCs have only been observed in radio wavelengths and have not been detected by optical or X-ray binoculars.
Original unknown
Researchers have put forward three theories to explain the origin of ORC. The first is that they are formed from shock waves in the center of their galaxy, such as when two supermassive black holes meet.
The second theory is that they are caused by the activity of the active galactic nucleus, the radio jets scattering particles to form the shape of the ORC. The third theory is that ORCs are shields caused by starbursts in the center of their galaxies. “Like a spy, we’re gathering more and more clues as to what the object might be,” says Koribalski.
Most of the ORCs found so far have been found using ASKAP, due to its vast area. While radio telescopes are generally able to see lunar-sized areas, ASKAP can scan an area 100 times larger. Once ASKAP saw ORC1, MeerKAT was used for more detailed monitoring because its higher resolution provides more sharp radio images.
“The ORC project is a perfect example of the clever use of MeerKAT by its users, playing to its strengths: ASKAP monitors large parts of the sky and can detect relatively rare objects; MeerKAT may then follow up to study them in more detail, “Fernando Camilo, chief scientist at the South African Radio Astronomy Observatory in Cape Town, said in a statement. The observatory builds and operates the MeerKAT.
Koribalski says other high-resolution radio telescopes around the world may soon point to these objects, especially when the next generation of these devices comes online in the next few years. It consists of a square kilometer array, which will have thousands of antennas on two sites in Australia and South Africa, and the next generation very large array in the United States.
“Without a doubt, radio astronomers will be attracted to this new type of object,” says Paseto.