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Astronomers Have Found Another Radio Source They Can't Explain


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

NGC 2082

The whole NGC 2082 galaxy emits normal amounts of radio waves, but from somewhere to one side comes a vastly more powerful emission. We don't know if the source is something within the galaxy, or something much more distant obscured at other frequencies by the galaxy in the way. Image Credit: Balzan et al/Astrophysics and Space Science

When Professor Miroslav Filipovic of the Western Sydney University assigned a promising young master's student a patch of the sky to study, he thought there might be something interesting in it. Filipovic was more right than he knew, with Joel Balzan turning up a strange radio source that, even with further exploration, no one has been able to explain. The team hopes future generations of radio telescopes will make sense of the anomaly.

Balzan was assigned to look at an area including NGC 2082, a spiral galaxy 60 million light-years away that hasn't been studied as much as its neighbors. Besides looking very similar to our own galaxy, the most interesting thing about NGC 2082 before this work was the presence of a type II supernova there in 1992.


Filipovic suspected NGC 2082 might have a supernova remnant worth studying. However, in a paper accepted for Astrophysics and Space Science (preprint on the pair and co-authors report something far more powerful and mysterious.

Balzan looked at data previously collected by ASKAP–EMU but not previously examined. Across NGC 2082 as a whole, he detected heightened radio emissions compared to the background, as would be expected from any galaxy, with a small peak close to the galactic center. However, Balzan also found a much more powerful peak, named J054149.24–641813.7, that looks as though it is coming from halfway between NGC 2082's center and its outer edge.

J054149.24–641813.7 is so powerful, and the emissions so interesting, Balzan and Filipovic sought time on the famous Parkes Dish to explore it in more detail and received approval almost straight away. As Filipovic noted to IFLScience, that's exceptionally rare when access to such a large telescope is so competitive.

However, the Parkes results, and studies with other types of telescopes, just deepened the mystery. “We see this ONLY in radio frequencies,” Filipovic told IFLScience, thus making it very unlikely the source is a star or some other object within our galaxy, or at least closer than NGC 2082. On the other hand, it's too bright at those frequencies to be a recent supernova in NGC 2082, “Or even a hypernova,” Filipovic added.


That leaves the possibility that J054149.24–641813.7 has nothing to do with NGC 2082 at all, and in fact, is something much more distant like a quasar. The chances of something like that hiding behind NGC 2082 are just 1.2 percent, the authors calculate, so it's not likely. On the other hand, it's less unlikely than anything else they can think of, Filipovic told IFLScience.

If J054149.24–641813.7 is a quasar or radio galaxy it will be almost impossible to determine that by seeing the galaxy around it, as NGC 2082 will block out light at most frequencies.

One way we may be able to get some clues to J054149.24–641813.7's nature would be to see whether it has been dimmed at the frequency known as HI. This region of the electromagnetic spectrum is absorbed by neutral hydrogen, so objects far away tend to be fainter there. So far, no studies with telescopes capable of detecting HI dimming with the appropriate resolution have been conducted in the relevant area. If one was, it might give us a good idea of the distance to J054149.24–641813.7, but that would only be the beginning of resolving the question of what it is.



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