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Crab Nebula Pulsar
In 1054 AD a supernova erupted in the constellation Taurus. That is the source of the nebula. The explosion of the massive star left behind the star's core still with a mass of about two Suns. It was compressed so hard that electrons and protons were forced together turning it into a giant neutron, about 10 km in diameter.
Because of the conservation of angular momentum the pulsar is spinning nearly 30 times per second. Jets of light and material pour out of its poles. Since one pole is aimed near us we see the jet flash about 30 times per second.
Some friends and I attached a speaker to a 14" telescope and drove it with a signal generator at nearly 30 Hz. This caused the stars to bounce back and forth. Over the exposure time of 30 seconds per frame the stars appeared as streaks. The pulsar, however, appeared stationary during each exposure. Since our oscillator wasn't exactly tuned to the pulsar's frequency, each frame shows the pulsar in a different spot in its path. Putting these together into a movie shows the pulsar appearing to bounce up and down.
Crab Nebula Pulsar
In 1054 AD a supernova erupted in the constellation Taurus. That is the source of the nebula. The explosion of the massive star left behind the star's core still with a mass of about two Suns. It was compressed so hard that electrons and protons were forced together turning it into a giant neutron, about 10 km in diameter.
Because of the conservation of angular momentum the pulsar is spinning nearly 30 times per second. Jets of light and material pour out of its poles. Since one pole is aimed near us we see the jet flash about 30 times per second.
Some friends and I attached a speaker to a 14" telescope and drove it with a signal generator at nearly 30 Hz. This caused the stars to bounce back and forth. Over the exposure time of 30 seconds per frame the stars appeared as streaks. The pulsar, however, appeared stationary during each exposure. Since our oscillator wasn't exactly tuned to the pulsar's frequency, each frame shows the pulsar in a different spot in its path. Putting these together into a movie shows the pulsar appearing to bounce up and down.