The Crab Nebula is the remnant from a supernova which exploded in 1054 A.D.
This event was recorded by Chinese and Arab astronomers, and perhaps by the
Anasazi natives in North America. The Chinese records indicate that this
exploding star was visible during the daylight for 23 days, and at night for
about 2 years. The red filaments faintly visible in this image are compressed
remains of the outer layers of the exploded star (the name "Crab Nebual" comes from
astronomical drawings in the mid-1800's, in which these filaments look like
legs on a crab), while the blue-white glow of the nebula is from high energy
electrons speeding along magnetic fields created by the "neutron star" left
behind by the explosion. This neutron star is the collapsed core of the original
star, now squeezed into a diameter of only about 30 kilometers.
It is so dense that a teaspoon of its material would weigh a billion
tons on earth! The rotational energy of the star being compressing into such
a small body also makes the neutron star rotate at an amazing 30 times each
second.

Image data:
Camera: Olympus OM-1
Film: Ektachrome 1600
Exposure: 15 minutes
Telescope: 10" Schmidt-Newtonian (image cropped and enlarged)