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Crab Nebula
The Fantastic World of the Neutron Star
 | Optical image of the Crab Nebula
(Credit: Palomar Obs.) |
Despite the intensity of the supernova explosion that created the Crab Nebula, some stellar material stayed
behind, and survived intact. An object called a neutron star was left. Crushed by
the titanic forces of the explosion, about 2 solar
masses of material remained out of the original 8-12 solar masses of the
exploded star. But, the crushed material was compressed into a volume no larger
than that of Manhattan Island, and its supporting bedrock! A mere thimbleful of
this star-stuff would contain the same mass as about 10 million full sized, African elephants!! These
stars are unbelievably dense!
And just as an ice skater spins faster and faster as she pulls her body closer
and closer to her rotation axis, as this star collapsed from the originally
slowly spinning parent object, it too began to spin more and more rapidly. The
magnetic field also increases greatly in strength. The combination of rapid
rotation and strong magnetic field is believed to generate jets of high-energy
particles that produce the pulses.
Several years after this discovery, it was found that the Crab Pulsar was very,
very gradually slowing down! This meant that it was losing energy. Remarkably,
when we calculated this loss of energy, it turned out to be almost precisely the
amount of energy necessary to power the Crab Nebula itself!!! In other words, the
pulsar in the Crab was "feeding" the nebula just the right amount of energy to
illuminate it as we see it today. The Crab Nebula is truly a beautiful sight in
the sky, when viewed through a telescope, and its history and evolution are no
less remarkable. It is probably the single most studied object in the heavens
today. Who knows what the future holds for it, and for our understanding of the
processes that shape its evolution?
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