The SKA’s the limit after sister telescope finds something very weird indeed

A telescope that’s a precursor to the Square Kilometre Array in SA has helped a group of scientists discover something very unusual: the core of a collapsed star that releases a giant burst of energy three times an hour.

It is unlike anything spotted by astronomers before, and has given the global science community a taste of what the SKA could uncover.

The team who discovered it think it could be a neutron star or a white dwarf with an ultra-powerful magnetic field.

White dwarfs and neutron stars are both the collapsed cores of stars, but in the case of the former they are low-mass stars (10 times less than the mass of the sun) and in the latter, very dense and massive ones, generally about 20km in diameter. 

The newly spotted strange object is spinning about in space. It sends out a beam of radiation that crosses our line of sight and, for a minute in every 20, is one of the brightest radio sources in the sky.

Astrophysicist Dr Natasha Hurley-Walker, from the Curtin University node of the International Centre for Radio Astronomy Research, led the team that made the discovery.

“This object was appearing and disappearing over a few hours during our observations,” she said. “That was completely unexpected. 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.”

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.

—  Astrophysicist Dr Natasha Hurley-Walker

The object was discovered by a student, Tyrone O’Doherty, using the Murchison Widefield Array (MWA) telescope in outback Western Australia and a new technique he developed.

“It’s exciting that the source I identified last year has turned out to be such a peculiar object,” said O’Doherty. “The MWA’s wide field of view and extreme sensitivity are perfect for surveying the entire sky and detecting the unexpected.”

Objects that turn on and off in the universe are called “transients”.

Co-researcher Gemma Anderson said “when studying transients, you’re watching the death of a huge star or the activity of the remnants it leaves behind”.

“Slow transients” — like supernovae — might appear over the course of a few days and disappear after a few months.

“Fast transients” — like a type of neutron star called a pulsar — flash on and off within milliseconds or seconds.

But Anderson said finding something that turned on for a minute was “really weird” and that, while this type of star existed theoretically, no one thought it would be directly detected as it was believed to be far less bright.

Hurley-Walker is now monitoring the object with the MWA to see if it switches back on.

“If it does, there are telescopes across the southern hemisphere and even in orbit that can point straight to it,” she said. “More detections will tell astronomers whether this was a rare one-off event or a vast new population we’d never noticed before,” she said.

MWA director Prof Steven Tingay said: “There are, no doubt, many more gems to be discovered by the MWA and the SKA in coming years.”