Crab Nebula, which gets its name from the shape, are the remains of a supernova that has become a pulsar that, with patience, you can see in the center of this.
This pulsar, a neutron star incredibly large mass, has its name by pressing the rotating speed and the emission of gamma rays as pulses. Rotates at a speed of 40 times per second, emitting such radiation pulses.
The image you see is a composition of the visible spectrum and X-ray transformed the visible spectrum, as almost all the images that have these colors as chanchis and many believe they are clusters of gas (which they are, but not visible).
Remarkable pieces of plasma supernova explosion, that light, I came to earth about the year 1000 and it was visible to the naked eye. Many history books speak of angels and stupidity of those gods (not exist) when referring to the explosion that should illuminate the sky a few months (just about two years).
The Crab Nebula is about 6500 light years in diameter and about 7 light-years, expanding at about 1500 km/s, almost-na.