ESO

There's a super weird reason this star flashes every 2 minutes

Don't blink.

FIONA MACDONALD
29 JUL 2016
 

Astronomers think they might have finally solved a stellar mystery that's been puzzling scientists for more than 40 years - why a strange star called AR Scorpii flashes brightly and fades every 2 minutes.

New observations show that the star system isn't just something we've never seen before, it's something astronomers have never even imagined could be possible before, and it serves as a reminder that we still know so very little about the phenomena within our Universe.

 

AR Scorpii lies around 380 light-years away in the Scorpius constellation, and when it was first discovered back in the 1970s, researchers put its strange flickering down to it being a lone variable star.

But, last year, an international team of amateur astronomers observed something more suspicious about its behaviour - the system seemed to be acting in a way scientists had never seen before.

Using a range of telescopes, including Hubble and the Very Large Telescope, the amateur astronomers teamed up with professionals to show that AR Scorpii is actually not one, but two stars. And they're locked together in an incredibly violent dance, orbiting each other once every 3.6 hours.

The duo is made up of a compact white dwarf the size of Earth but 200,000 times more massive, and a cool red dwarf which is one-third the size of our Sun.

The regular flashing arises, they predict, because the white dwarf spins so fast that it energises electrons up to almost the speed of light, creating a cosmic whip that lashes its red dwarf partner, triggering the release of a huge pulse of electromagnetic radiation every 1.97 minutes – hence the flashing.

Curiously, the radiation pulse ranges hugely from ultraviolet to radio frequencies. 

 

"The strength of the pulsations are unprecedented," lead researcher Thomas Marsh from the University of Warwick in the UK told Gizmodo's Maddie Stone.

In the past, this type of pulsing has been observed in neutron stars, which are formed by the collapse of a star after it explodes.

But although a few people have predicted that white dwarfs could show similar behaviour, no one's ever expected it to be coming from a bizarre binary system like this.

Even stranger, the astronomers have no idea where those super-charged electrons are coming from – while it seems that they're most likely associated with the spinning of the white dwarf, they could also be coming from the cooler red dwarf.

"The high energy electrons are also very unusual – there is only one other system like this, and relativistic electrons are hard to understand when it comes to white dwarfs which generally do not show high-energy phenomena," said Marsh.

"I think this is what excites me most – it could be that we are seeing a new form of cosmic particle accelerator."

The researchers have now published the results in Nature (read the full paper here), and while it's exciting that we've found a never-before-seen type of binary star system, it's equally unnerving, seeing as there could be more of these violent duos throughout the Universe.

The team will continue to use a range of telescopes around the world to monitor the star system, including the XMM-Newton X-ray satellite to pick up radio and X-ray emissions, with the hope of being able to narrow down further where the super-charged electron whip is coming from.

In the meantime, let's just all be grateful that we're not living around a star that's getting whipped every 1.97 minutes by a mysterious particle accelerating whip. The Universe is a pretty brutal place.

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