GLAST: Exploring the Extreme Universe
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by Robert Naeye and David J. Thompson
A long time ago, in a galaxy far, far away, the core of a massive star implodes under the crushing force of gravity. As the core scrunches down into a black hole, magnetic fields channel infalling gas into two blazing jets of subatomic particles. As the beams punch out of the dying star, protons collide at incredible speeds, generating shock waves that send a burst of gamma rays screaming through the universe.
Fast forward 10 billion years. The photons from this gamma-ray burst have raced across immense tracts of mostly empty space. Cosmic expansion has literally stretched their wavelengths, sapping their energy. But they still pack a powerful punch. Just one of these gamma-ray photons carries a billion times more energy than the light we see with our eyes.
Eventually, the photons smack into the thin atmosphere of planet Earth. The photons have traversed an unfathomable distance unscathed. But when they smash into gas molecules, they go splat and decay into a shower of particles and photons. It's a pity for Earth's astronomers that the information carried by those photons is lost forever.
But soon that situation will change.
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