Discovery of mysterious circular ring points to intergalactic origin

Western Sydney University researchers, together with an international team of experts, have discovered a mysterious circular ring near our neighbouring galaxy that could be the first known case of an intergalactic Supernova Remnant – remains of an exploded star that could be up to 7000 years old.

Dubbed a ‘rogue’ Supernova Remnant by the researchers and named J0624–6948, it is most likely located in the Large Magellanic Cloud (LMC) – a satellite galaxy of the Milky Way – and its position suggests a previously unobserved origin.

Published in the prestigious Monthly Notices of the Royal Astronomical Society, lead author Professor Miroslav Filipovic from the University’s School of Science said the discovery was exciting and raised many unanswered questions.

“When we originally discovered this almost perfectly circular radio object we thought it was yet another ORC (Odd Radio Circle) but after our additional observations, it became clear that this object is much more likely to be something else,” said Professor Filipovic.

The ring discovered has significant differences to the five other known ORCs — a flatter radio spectral index, lack of a prominent central galaxy as a possible host, and larger apparent size — that all suggest it may be a different type of object.

“The most plausible explanation is that the object is an intergalactic Supernova Remnant due to an exploded star that resided in the Large Magellanic Cloud outskirts that had undergone a single-degenerate type Ia supernova which involves the explosion of two stars orbiting each other,” said Professor Filipovic.

“However, we considered other scenarios such as that this object might represent a remnant of the super-flare activity from a nearby Milky Way star (at only 190 light years away from Sun) that happened only a few centuries ago, or the premise that it may in fact be a much larger ORC.

“What we’ve potentially then discovered is a unique remnant of supernova that has expanded into a rarefied, intergalactic environment — an environment that we didn’t expect to find in such an object. Our estimates point to the age of about 2200 to 7100 years old.”

J0624–6948 was first detected with the Australian Square Kilometre Array Pathfinder (ASKAP) managed by CSIRO – one of several new generation radio telescopes that are revealing new features of the Universe.

“These new radio telescopes can pick up a range of spherical objects, and due to the combined effects of high-sensitivity, good spatial sampling, and wide area coverage, they are enriching our understanding of the Universe.”

For more information, download Mysterious Odd Radio Circle near the Large Magellanic Cloud – An Intergalactic Supernova Remnant? here (opens in a new window).


30 March 2022

Ali Sardyga, Senior Media Officer