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Look,
Up In the Sky!
The Crab Nebula is a huge mass of blue haze and twisted clumps
of red gas located about 6,500 light years from Earth. It is a gigantic
explosion cloud--the tortured remains of a supernova explosion first
seen in 1054 A.D., almost a thousand years ago. Even though the
explosion started a long time ago, the cloud is still expanding.
The reddish clumps are moving outward with speeds near 2,000 kilometers
per second--about 4 million miles per hour. The cloud, now about
10 light years from end to end, has engulfed many star systems.
If life existed on planets in any of those star systems, it would
now be struggling to survive. The cloud thins as it expands and
is so far away that it poses no threat to Earth. Image
courtesy of the European Southern Observatory.
In this alternate
explanation of the dinosaurs' disappearance, a huge star close to
the solar system exploded, showering Earth with intense light and
high-energy particles. Such explosions, called supernovae, are triggered
in different ways. Most supernovae result from the explosion of
very large and bright stars or the binary companions of bright stars.
If a supernova caused the extinction of the dinosaurs, the pre-explosion
star would had to have been close to Earth and very bright in the
night sky like the "Dinostar" of our story. Every supernova
releases enormous amounts of electromagnetic radiation, or light,
including X-Rays and Gamma rays. Nuclear reactions like those in
man-made nuclear explosions occur in supernovae, making huge amounts
of radioactive matter. The radioactive matter is thrown out into
space by the supernova blast. As the light and matter from the explosion
expand outward, they become less concentrated and less deadly. But
for any life forms within about fifty light years of a supernova,
the effects would be devastating.
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