Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2002 July 14 
Posted on 07/14/2002 1:44:33 PM PDT by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2002 July 14
Explanation: The Crab Nebula, filled with mysterious filaments, is the result of a star that was seen to explode in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers. The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture taken recently from a Very Large Telescope, the color indicates what is happening to the electrons in different parts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while blue indicates the electrons are whirling around the magnetic field of the inner nebula. In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.
A pulsar's magnetic field is so strong that it causes most of the light and radiation that the neutron star emits to be concentrated into cones of emission, like beams from a lighthouse. In fact, the key to a pulsar is the combination of the extraordinary magnetic field and the rotation of a neutron star. If the neutron star is spinning, like the Earth rotates on its axis, and if the Earth happens to lie in the path of the beams, we see a pulse of light each time a beam sweeps across the earth.
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A sequence of images showing the flashes at visible wavelengths from the Crab pulsar, located at the center of the Crab Nebula. Credit: National Optical Astronomy Observatories
Here's the Chandra x-ray image of the central part of the Crab.
Chandra's X-ray image of the Crab Nebula directly traces the most energetic particles being produced by the pulsar. This amazing image reveals an unprecedented level of detail about the highly energetic particle winds and will allow scientists to probe deep into the dynamics of this cosmic powerhouse.
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