“I think it’s real,” Curtin University student Tyrone O’Doherty told his supervisors when he spotted the anomaly.
And it was real, as it turns out. The object beaming out from space was also “spooky”, and “in our galactic back yard”.
An Australian team studying the universe’s radio waves has discovered a new type of beam that comes and goes, one of the brightest radio sources in the sky. The details of the discovery were published in Nature on Thursday.
When something in space switches on and off it’s called a “transient”. It might come from a pulsar, which flashes on and off in milliseconds or seconds. Or a supernova that might appear for a few days before disappearing again.
“What we found, though, is something that switches on and off every 20 minutes,” astrophysicist Dr Natasha Hurley-Walker said.
“It was kind of spooky for an astronomer because there’s nothing known in the sky that does that. And it’s really quite close to us – about 4,000 light years away. It’s in our galactic backyard.”
Hurley-Walker is from the International Centre for Radio Astronomy Research’s Curtin University node. She was also O’Doherty’s supervisor, and the lead author on the Nature article.
She uses the Murchison Widefield Array in outback Western Australia, a radio telescope, to survey the sky. For his honours thesis, O’Doherty joined her team and had created some coding software to search through data for transients.
“He found something,” she said. Pictures from the array show the Milky Way, with a bright dot marking the location of the object. “Just to the right, there’s a source that is a supermassive black hole, throwing jets of radio waves into space at nearly the speed of light.
“Admittedly, it’s further away. But this radio transient that we saw is about as bright as that. So that’s really extreme. And we did not expect to find anything so bright.”
Using the frequencies of the radio waves, she worked out the object is not very far away – as space goes.
Its behaviour matches something that has been predicted to exist, but never observed – an “ultra-long period magnetar”, a type of slowly spinning neutron star. Or it could be that a collapsed star became a white dwarf pulsar, but that is very unlikely. Whatever it is, it’s “really extreme physics”, Hurley-Walker said.
“And, of course, it could be something that we’ve never even thought of.”
For O’Doherty, creating the software was the thesis – actually using it to find the object was a bonus.
“In the closing weeks of the project I was going through them to see if I had anything real … I found this one candidate that looked real at first,” said O’Doherty, who is now doing his PhD.
“I kept doing more and more tests and it kept continuing to appear real, which was awesome. Then I detected it again. I 100% confirmed it was real and not just a one-off thing.”
Hurley-Walker said the mission was now to try to find more of the objects. Meanwhile, the world’s largest radio telescope is being built, with the low-frequency part of it destined for the WA desert. That will mean far more data and more discoveries.
“We will be making new discoveries, things we didn’t predict, all the time,” Hurley-Walker said.
“The universe is full of wonders.”
