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.