Source:BBC
http://news.bbc.co.uk/hi/english/sci/tech/newsid_183000/183133.stm

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