Exploding stars excite astronomers worldwide
An explosion caused by two stars some 5,000 light years from Earth has been exciting astronomers in observatories worldwide, a UK conference heard today.
Scientists have been given fresh insight into how stars explode thanks to a spectacular blast caused by a couple of celestial bodies nicknamed Red Giant and White Dwarf, Royal Astronomical Society members were told.
Drawn together in close orbit, the two stars’ atmospheres have created an explosion 10 times the heat of the sun’s core.
Its power is the equivalent of the Earth thrown across space at several thousand miles a second.
The event was first spotted in February by amateur star-gazers, who reported a faint star in the constellation of Ophiuchus suddenly becoming clearly visible without the aid of a telescope.
Records show the “recurrent nova” has been this bright five times before in the last 108 years, most recently in 1985.
But astronomers have been able to observe the latest explosion in unprecedented detail thanks to an “armada” of space- and ground-based telescopes.
Speaking today at the RAS national astronomy meeting in Leicester, Professor Mike Bode of Liverpool John Moores University and Dr Tim O’Brien of Jodrell Bank Observatory presented results from the telescopes.
Speaking afterwards, Prof Bode said: “This is an exciting opportunity that has brought together astronomers from across the globe.
“They have been working around the clock with some of the most advanced technology to really get to grips with these explosions.”
The supernova, called RS Ophiuchi (RS Oph), consists of a white dwarf star (the super-dense core of a star, about the size of the Earth, that has reached the end of its main hydrogen-burning phase of evolution and shed its outer layers) in close orbit with a much larger red giant star.
The two are so close together that hydrogen-rich gas from the outer layers of the red giant is continuously pulled on to the dwarf by its high gravity.
After around 20 years, enough gas has been gathered to trigger a runaway thermonuclear explosion on the white dwarf’s surface.
In less than a day, astronomers found, its energy output increases to more than 100,000 times that of the sun, and the gathered gas, several times the mass of Earth, is ejected into space at speeds of several thousand miles per second.
Astronomers have also seen that the red giant is losing enormous amounts of gas in a wind that envelops the whole system.
As a result, the explosion on the white dwarf occurs “inside” its companion’s extended atmosphere and the ejected gas then slams into it at very high speed.
“In 1985, we were not able to begin observing RS Oph until nearly three weeks after the outburst, and then with facilities that were far less capable than those available to us today,” said Dr O’Brien.
“Both the radio and X-ray observations from the last outburst gave us tantalising glimpses of what was happening as the outburst evolved.
“In addition, this time, we have developed very much more advanced computer models.
“The combination of the two now will undoubtedly lead to a greater understanding of the circumstances and consequences of the explosion.”
