Astronomers have discovered a strange intergalactic ring that may be the first of its kind found. The large radio circle lurks between the Milky Way and a neighboring galaxy, and its discoverers suggest it may be the remains of an unusual supernova.
The object, officially designated J0624-6948, was spotted using the ASKAP radio telescope array, and at first the astronomers assumed to be another example of an odd radio circle (ORC). This recently discovered class of astronomical anomaly is exactly what it sounds like – a circle of radio emission that’s so far unexplained, although astronomers may be closing in on some answers.
But this new ring has a few features that differ from known ORCs. Most odd radio circles tend to envelop entire galaxies, but this new object is located in intergalactic space. It also appears more than three times bigger in the sky than most ORCs. Its radio spectral index is also a lot flatter, all of which lead the astronomers to conclude that it’s a different type of object altogether.
The scientists propose it may in fact be a “rogue” supernova remnant. These clouds of materials are ejected from the explosive deaths of stars, but this would be the first time one has been discovered outside of a galaxy – although it may have originally come from the Large Magellanic Cloud, a dwarf galaxy that orbits the Milky Way.
“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 Miroslav Filipovic, lead author of the study. “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.”
If it is an intergalactic supernova remnant, the team estimates that it’s probably between 2,200 and 7,100 years old. Other possible explanations include the remnant of a super-flare from a nearby Milky Way star, or an unusually large ORC. After all, only five ORCs have been described so far, so we don’t know very much about them.
Further observations could help unravel the mystery.
The research was published in the journal Monthly Notices of the Royal Astronomical Society.
Source: Western Sydney University