‘That was completely unexpected,’ says one scientist. ‘It was kind of spooky for an astronomer because there’s nothing known in the sky that does that’
Scientists have spotted a “mysterious” object letting out giant blasts of energy, three times an hour.
Whatever the object is – which is relatively nearby, at 4,000 lightyears away – it is nothing like astronomers have ever seen before.
“This object was appearing and disappearing over a few hours during our observations,” said Natasha Hurley-Walker, from the International Centre for Radio Astronomy Research, who led the research
“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 4000 lightyears away. It’s in our galactic backyard.”
The object could be a neutron star or a white dwarf, astronomers speculate, that has an incredibly powerful magnetic field.
It is spinning around quickly in space so that the beam of radiation flashes towards us three times every hour. For one minute out of every twenty, it becomes one the brightest radio sources in the whole sky.
A student at Curtin University, named Tyrone O’Doherty, was the first to spot the object using the Murchison Widefield Array (MWA) telescope in outback Western Australia. Since it was found, it has turned out to perplex the astronomers who have studied it.
“It’s exciting that the source I identified last year has turned out to be such a peculiar object,” said Mr O’Doherty, who is now studying for a PhD at Curtin.
“The MWA’s wide field of view and extreme sensitivity are perfect for surveying the entire sky and detecting the unexpected.”
There are a wide array of different objects in space that turn off and on, which are given the name “transients”. Usually, they come from the death of a massive star or the flickering remnants that are left behind when that happens.
They can go fast – like a neutron star, called a pulsar, which can flash on and off in miliseconds – or they can go slowly, happening over a few days, as in the course of supernovae.
But something in the middle, like the new object, is very unusual.
There are yet more mysteries about the object. It is incredibly bright, but smaller than the sun, and shoots out highly-polarised radio waves. That would indicate that it has a very strong magnetic field.
Taken together, those characteristics seem to match an object known as an ultra-long period magnetar. But such an object has never actually been seen before – and it came as a surprise.
“It’s a type of slowly spinning neutron star that has been predicted to exist theoretically,” said Dr Hurley-Walker.
“But nobody expected to directly detect one like this because we didn’t expect them to be so bright.
“Somehow it’s converting magnetic energy to radio waves much more effectively than anything we’ve seen before.”
Scientists are now watching the the area intently in the hope that it will switch back on. If it does, they will be able to point telescopes towards it in the hope of learning more.
They will also look through the archives of observations from the MWA to see whether there are other examples of such objects that have been missed in the past. “More detections will tell astronomers whether this was a rare one-off event or a vast new population we’d never noticed before,” said Dr Hurley-Walker.
A paper describing the research, ‘A radio transient with unusually slow periodic emission’, is published today in Nature.