Astronomy’s latest mystery objects, the strange radio circle or ORC, have been increasingly drawn into attention by an international team of astronomers using the world’s most capable radio telescopes.
When first revealed in 2020 by the ASKAP radio telescope owned and operated by Australia’s national science agency CSIRO, strange radio circles quickly became a point of fascination. Theories on their cause ranged from galactic shockwaves to the throes of wormholes.
A new detailed image, captured by the South African Radio Astronomy Observatory’s Meerkat radio telescope and published today Monthly Notices of the Royal Astronomical Societyis providing researchers with more information to help nail down those theories.
There are now three major theories to explain the causes of orcs:
- They may be the remains of a massive explosion at the center of their host galaxy, such as the merger of two supermassive black holes;
- They could be powerful jets of energetic particles emanating from the center of the galaxy; or
- They may be the result of a starburst ‘termination shock’ from the production of stars in the Milky Way.
To date ORCs have only been detected using radio telescopes, with no indication of them when researchers look for them using optical, infrared, or X-ray telescopes.
Dr Jordan Collier of the Inter-University Institute for Data Intensive Astronomy, who compiled the image from Meerkat data, said that continuing to observe these anomalous radio circles will give researchers more clues.
Collier said, “People often want to interpret their observations and show that it aligns with the best of our knowledge. To me, it’s more exciting to discover something new that defies our current understanding.”
The rings are huge – about a million light years, 16 times larger than our own galaxy. Despite this, odd radio circles are difficult to see.
Professor Ray Norris of Western Sydney University and CSIRO, one of the authors on the paper, said only five strange radio circles have been detected in space.
“We know that ORCs are rings of faint radio emission around a galaxy with a highly active black hole at its center, but we don’t yet know what causes them, or why they are so rare,” said Professor Norris said.
For now, ASKAP and MeerKAT are working together to find and describe these objects quickly and efficiently, said Professor Ellen Sadler, chief scientist at CSIRO’s Australia Telescope National Facility, which includes ASKAP.
“Almost all astronomy projects are made better by international collaboration – both with the teams of people involved and the technology available,” Professor Sadler said.
“ASKAP and MeerKAT are both precursors to the International SKA Project. Our developing understanding of anomalous radio circles is enabled by these complementary telescopes working together.”
To really understand the strange radio circles, scientists will need access to even more sensitive radio telescopes such as the SKA Observatory, which is supported by more than a dozen countries, including the UK, Australia, South Africa, France, Canada, China and India.
“There is no doubt that the SKA telescope, once built, will find many more ORCs and will be able to tell us more about the lifecycle of galaxies,” Professor Norris said.
“Until SKA becomes operational, ASKAP and MeerKAT are set to revolutionize our understanding of the universe faster than ever before.”
ASKAP is based in the country of Wajari Yamatji in Western Australia, and MeerKAT is based in the Northern Cape province of South Africa.
material provided by CSIRO Australia, Note: Content can be edited for style and length.