White dwarfs can mimic black holes

Washington, December 19 (ANI): Bright X-ray flares in nearby galaxies, once assumed to indicate the presence of black holes, can in fact be produced by white dwarfs, a new research has revealed.

Astronomers from the University of Southampton-along with colleagues in Taiwan, South Africa, Poland, Australia and Italy-made the discovery by detecting a dramatic, short-lived X-ray flare that was picked up by an X-ray telescope on the International Space Station.

Using optical telescopes in South Africa and Chile, the Southampton astronomers showed that the flare, called XRF111111 as it happened on 11 November 2011, was located in the Small Magellanic Cloud. The Magellanic Clouds are between 160,000 and 200,000 light-years away and are the nearest satellite galaxies to the Milky Way. They are visible to the naked eye from the Southern Hemisphere.

The flare from XRF111111 was so luminous that astronomers initially thought it was likely to be a black hole producing X-rays but further research by researchers Professor Phil Charles, Professor Malcolm Coe and postgraduate student Liz Bartlett revealed that its X-ray temperature was so low that it had to be a white dwarf instead.

White dwarfs are very common, burnt-out cinders of normal stars like the Sun that are typically about one solar mass but are contained in a volume no bigger than the Earth.

However, white dwarfs were not considered capable of producing such a huge X-ray flash but the optical observations in South Africa and Chile showed that the white dwarf was orbiting a hot B star-a normal star about 10 times the mass of our Sun that is much hotter and brighter. This was something that had only been seen twice previously and both times with much lower X-ray luminosities.

Research by Professor Charles and his team revealed that material was probably collecting on the surface of the white dwarf from the B star and eventually underwent runaway thermonuclear burning that was seen on Earth as a nova explosion.

"Our observations show that the thermonuclear burning probably caused a shell of matter to be ejected from around the white dwarf and when the shell hit the hot wind of the B star it produced a huge shock leading to the X-ray flash that was seen on the International Space Station," said Professor Charles.

"We think that this incredible X-ray flash was not due to accretion onto a black hole but was instead due to a nova explosion on a white dwarf that took place close to a hot massive star. This was something that we, as astronomers, have never seen before.

"This surprising result shows that, in the right circumstances, white dwarfs are capable of mimicking black holes, the most luminous objects we know of," he added.

The research has appeared in The Astrophysical Journal. (ANI)

Matches

MORE TOP STORIES TODAY

Punjab pull off another big chase

Punjab pull off another big chase

GAME 7, SHARJAH—Maxwell, Miller, Pujara chase down Rajasthan's 192. More »

Royal test for Kings

Royal test for Kings

Preview — Clash of philosophies between Australia-centric teams More »

Have nothing to prove to anybody — Sehwag

Have nothing to prove to anybody — Sehwag

The Nawab of Najafgarh says a good run in IPL could help his chances of a comeback on India's tour to England in June. More »

Shastri in proposed IPL probe panel

Shastri in proposed IPL probe panel

Some members stressed on the need for proposing names with an "impeccable record and clean image". More »

Duminy steals first win for Delhi

Duminy steals first win for Delhi

Furious fifties by Duminy and Dinesh Karthik end a long losing streak for the Daredevils. More »

Five things England must do to bounce back

Five things England must do to bounce back

England have appointed a new head coach in Peter Moores. More »

AB, Parthiv seal Bangalore's second win

AB, Parthiv seal Bangalore's second win

Royal Challengers overcame a stutter to cruise to the small target they were set by Mumbai Indians. More »

‘Felt like helpless minority’

‘Felt like helpless minority’

Former BCCI treasurer Ajay Shirke says emotions got the better of Srinivasan and he tried to oversimplify things by calling Meiyappan an “enthusiast.” More »

Srinivasan can attend BCCI meeting

Srinivasan can attend BCCI meeting

His status as president of TNCA makes him eligible to attend the Working Committee meeting on Sunday. More »

No way back for Pietersen: ECB

No way back for Pietersen: ECB

Kevin Pietersen's hopes of reviving his international career appeared to end Saturday when ECB managing director Paul Downton said there was 'no way back'… More »

The world record that nearly wasn't

The world record that nearly wasn't

Twenty years ago this week, Brian Lara became Test cricket's highest scorer, but he almost didn't make it. More »

Maxwell carves his parallel universe

Maxwell carves his parallel universe

Glenn Maxwell seems to project an icy disdain when at the crease. Match situations rarely faze him and the bubble in which he plays excludes everyone … More »

Moores gets second stint as coach

Moores gets second stint as coach

In a two-year spell from 2007 to 2009, the 51-year-old Moores led England in seven Test series. More »

Bangladesh senior players to see shrink

Bangladesh senior players to see shrink

Bangladesh's senior players will have three sessions with a psychological skill development coach later this month More »

BCCI is not anybody’s property — Dalmiya

BCCI is not anybody’s property — Dalmiya

Dalmiya feels that Srinivasan’s ‘power hungry’ attitude isn’t helping matters. More »

Tough for bowlers: Saeed Ajmal

Tough for bowlers: Saeed Ajmal

The 36-year-old believes the T20 format and rule changes in 50-over matches have made a real difference. More »

KP ridicules idea of day-night Tests

KP ridicules idea of day-night Tests

Kevin Pietersen has ridiculed the idea of day-night Test cricket, saying the game would be so different to proper Test cricket that we will need a whole… More »

Rajasthan edge low-scoring thriller

Rajasthan edge low-scoring thriller

The bowlers restricted Hyderabad to 133 for 6 before Rahane and Binny took Rajasthan over the line. More »

Maxwell blitz takes Punjab home

Maxwell blitz takes Punjab home

The Kings XI batsman blasted a 43-ball 95 to help his team pull off a massive chase against Chennai Super Kings. More »

BCCI members want independent probe

BCCI members want independent probe

The board members are realising after the Supreme Court's observations that something has to be done — IS Bindra More »

'BCCI lacks leaders to take on Srini'

'BCCI lacks leaders to take on Srini'

Two former BCCI presidents, Shashank Manohar and Jagmohan Dalmiya, have reacted strongly to the news of the BCCI calling an emergent meeting on Sunday… More »

Delhi look for first points against confident Kolkata

Delhi look for first points against confident Kolkata

Preview — The threat of Sunil Narine looms large again. More »

Bangalore vs Mumbai: A battle of the big-hitters

Bangalore vs Mumbai: A battle of the big-hitters

Preview — Given the firepower in both line-ups, Dubai crowd may see another high-scorer More »

Yuvraj tees off to Sharjah's delight

Yuvraj tees off to Sharjah's delight

Yuvraj Singh was hardly convincing to begin with against Delhi, but a big dose of crowd support and a helping of poor bowling meant he had the opportunity… More »