Strange flashing object discovered in deep space puzzles astronomers

Australia Broadcast Center

4 days ago

In the past few years, astronomers have recorded a handful of very strange radio signals, mostly coming from towards the centre of the Milky Way.
Armed with increasingly powerful telescopes, they've detected objects that emit powerful bursts of energy a few times an hour, like a chiming clock — and then fall silent.
The source of these "long-period radio transients", or LPTs, hasn't been nailed down, but it was thought they were caused by dead stars.
But a newly discovered LPT, reported in the journal Nature, could shift our view about the origin of these mysterious objects.
Unlike previous discoveries, this LPT also sends out X-ray pulses, making it the strangest one yet.
An international team, led by Curtin University astronomer Ziteng Andy Wang, first detected a radio signal in data captured by the Australian Square Kilometre Array Pathfinder telescope (ASKAP) in Western Australia.
Dubbed ASKAP J1832-0911, the object sent out radio waves for two minutes every 44 minutes.
By chance the signal was also spotted by NASA's Chandra X-ray Observatory on Valentine's Day last year.
Dr Wang said he was "pretty surprised" when he saw pulses of X-rays happening at the same time as the radio waves.
"That is a huge discovery," Dr Wang said.
The X-ray and radio pulses were emitted for a few weeks, and then fell silent.
Had Chandra not been observing that patch of sky, the X-ray bursts would never have been detected.
Astronomers have known about flashing objects since the 1960s, but until a few years ago, each one that had been recorded flickered very quickly, switching on and off every few seconds or minutes.
Then, in 2022, an Australian-led team discovered an LPT which emitted super-bright radio waves regularly over hours. A handful of other LPTs have been discovered since.
Researchers have proposed different theories for the source of these LPTs.
One is a super-dense star called a neutron star that spins, regularly hitting Earth with a beam of energy from its poles.
But these stars were thought to only be detectable when they were spinning very quickly, becoming too faint to see as they slowed down to LPT-level speeds.
Or they could be weaker dead stars — white dwarfs — in binary systems, interacting with other stars.
Michael Cowley, an astronomer at Queensland University of Technology who wasn't involved with the new research, pointed out a pre-print study from last year which supported this second theory.
"This seemed like a reasonable answer and a promising step toward solving the puzzle," Dr Cowley said.
But he said the detection of X-rays coming from ASKAP J1832-0911 "throws a spanner in the works".
"Pulsed X-rays are usually associated with rotating neutron stars," Dr Cowley said.
He believed this meant that LPTs could be coming from several different sources.
"My takeaway is that LPTs don't appear to be a single phenomenon. Instead, they may represent a new category of objects, defined not by a shared origin but by how they behave."
Dr Wang said it wasn't clear whether the new observation could be a white dwarf or a neutron star.
"Both are possible, but personally I would prefer an isolated neutron star," he said.
Whichever it is, the object has an extremely strong magnetic field, several billion times that of the Earth.
This makes them very difficult to learn more about, according Stuart Ryder, an astronomer at Macquarie University who also wasn't involved with the research.
"They're such extreme states of matter, we don't really have a good understanding of them because we can't replicate that here on Earth," Dr Ryder said.
But the sheer weirdness of the object presents other opportunities.
As radio telescopes improve, and more LPTs are discovered, they may help physicists understand how matter works in strange environments.
"If we can study extra-strong magnetic fields in objects and elsewhere in the Universe, then we can learn a lot about the physics of matter," Dr Ryder said.
He believes that understanding this extreme magnetism could help nudge science closer to clean nuclear fusion energy on Earth.
"At the end of the day, a star is basically just a natural form of a fusion reactor, and we're trying to replicate those conditions in a very controlled manner here on Earth."