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Tuesday, September 29, 1998 Published at 17:31 GMT 18:31 UK


Sci/Tech

Deep space blast disrupts our atmosphere

The Ulysses probe detected the burst

By our science editor Dr David Whitehouse

On the night of 27 August the Earth's upper atmosphere was bathed briefly by an invisible burst of high energy radiation from deep space.

The pulse of energy, the most powerful detected to strike the Earth from beyond the solar system, had a significant effect on the planet's upper atmosphere, scientists say.

It is the first time that a significant change in the Earth's atmosphere has been traced to a distant star.

Professor of Electrical Engineering at Stanford University in California, Umran Inan, said: "It was as if night was briefly turned to day in the ionosphere."

The energy pulse came from a distant star designated SGR 1900+14. It lasted just five minutes but scientists estimate that the pulse contained enough energy to power all of human civilisation for a billion billion years.

The object 1900+14 is believed to be a superdense star called a neutron star whose gravity pulls material from a nearby star.

This material comes crashing down onto the neutron star becoming superhot and finally exploding sending out a titanic burst of energy.

Five-minute disturbance

Scientists at Stanford operate a string of radio receivers across North America designed to monitor the state of the ionosphere, the region between 60 and 80 kilometres high. It detected a severe, five-minute disturbance on 27 August.

During that time the ionosphere pulsed to a five-second rhythm. This is the orbital period for the 1900+14 neutron star to rotate.

The burst was also picked up by the deep space Ulysses spaceprobe that is orbiting the Sun 600 million miles away.

This is not the first time that a stellar burst from outside the solar system is believed to have affected the Earth. Other events may have been observed in 1983 and 1996.

It is however the first time that there is definite evidence for such an effect.

Although there was no danger to life on Earth, the pulse was far too weak for that, scientists do believe that if a star exploded in our local cosmic neighbourhood its radiation could affect our atmosphere and sterilise the Earth's surface.



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