Scientists have detected a flash of light from across the Galaxy so powerful that it bounced off the Moon and lit up the Earth's upper atmosphere. The flash was brighter than anything ever detected from beyond our Solar System and lasted over a tenth of a second. NASA and European satellites and many radio telescopes detected the flash and its aftermath on December 27, 2004. Two science teams report about this event at a special press event today at NASA headquarters. A multitude of papers are planned for publication.
The scientists said the light came from a "giant flare" on the surface of an exotic neutron star, called a magnetar. The apparent magnitude was brighter than a full moon and all historical star explosions. The light was brightest in the gamma-ray energy range, far more energetic than visible light or X-rays and invisible to our eyes.
Such a close and powerful eruption raises the question of whether an even larger influx of gamma rays, disturbing the atmosphere, was responsible for one of the mass extinctions known to have occurred on Earth hundreds of millions of years ago. Also, if giant flares can be this powerful, then some gamma-ray bursts (thought to be very distant black-hole-forming star explosions) could actually be from neutron star eruptions in nearby galaxies.
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A neutron star is the core remains of a star once several times more massive than our Sun. When such stars deplete their nuclear fuel, they explode -- an event called a supernova. The remaining core is dense, fast-spinning, highly magnetic, and only about 15 miles in diameter. Millions of neutron stars fill our Milky Way galaxy.
Scientists have discovered about a dozen ultrahigh-magnetic neutron stars, called magnetars. The magnetic field around a magnetar is about 1,000 trillion gauss, strong enough to strip information from a credit card at a distance halfway to the moon. (Ordinary neutron stars measure a mere trillion gauss; the Earth's magnetic field is about 0.5 gauss.)
