Astronomers believe they have discovered evidence of a lone rogue star's death for the first time.
A mysterious and remarkably neat circle emitting radio waves has been detected, hanging in space, not far from the Large Magellanic Cloud, a satellite galaxy orbiting with the Milky Way, and named J0624-6948.
There's a reason why it sounds so familiar. Several mysterious, radio-emitting space circles known as Odd Radio Circles, or ORCs, have recently perplexed astronomers.
Astronomer Miroslav Filipovic of the University of Western Sydney in Australia noticed the resemblance.
"When we originally discovered this almost perfectly circular radio object we thought it was yet another ORC," Filipovic said. "But after our additional observations, it became clear that this object is much more likely to be something else."
The Australian Square Kilometre Array Pathfinder (ASKAP), one of the world's most powerful radio telescopes, was used to discover ORCs for the first time. These objects appeared to be massive and far away, with various distinguishing features, including a galaxy in the dead center.
The ORCs are presently thought to be the outcome of an energetic activity in those center galaxies, albeit the nature of that process remains unknown.
In fact, it's very likely that ORCs are spheres. Because of perspective, they look as rings at the margins, where there is a higher density of emission along our line of sight.
However, there are a few significant distinctions between J0624-6948 and ORCs. The absence of an identifiable core galaxy in J0624-6948 is significant, but not decisive. The spectral index of the radio emission is flatter than that of other ORCs, and the apparent size of J0624-6948 is bigger than that of other ORCs.
Filipovic and his colleagues investigated a variety of scenarios that could result in an item that resembled their observations. A considerably larger ORC, as well as a super-flare originating in a star near the galactic center, or jets from a distant active supermassive black hole, were among these.
Finally, one theory emerged as the most congruent with the observed behavior.
"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," Filipovic explained.
J0624-6948 would be the first intergalactic supernova remnant ever discovered, a bubble-like sphere of ejecta flowing outwards, if the scientists are correct. J0624-6948 would be roughly 155 light-years across if it were to be associated with the Large Magellanic Cloud, according to the team's calculations.
Follow-up observations may be able to shed light on the uncertainty. More observations with instruments like ASKAP and its South African counterpart MeerKAT could also aid in the identification of more unusual radio circles in the sky.
The research has been published in the Monthly Notices of the Royal Astronomical Society.