The image below is a color-enhanced image of the Crab Nebula. The earliest records of this nebula date back to the eleventh century AD when the ancient Chinese astronomers and the Pueblo people of New Mexico and Arizona (the Anasazi) recorded their observations of the night sky. The Crab Nebula was created by a supernova of a single, massive star; this supernova was so powerful that it lit up the sky in daylight for 23 days and 653 days to the naked eye in the night sky. When a star can no longer undergo fusion because of the lack of elements in the core (only iron is left), the star begins to swell while the core yields to the gravitational force because of the lack of thermal pressure and begins to shrink. The total gravitational collapse of the star lasts less than a second. During this time period, the iron atoms in the hot, dense core are crushed together. At first the force of gravity overcomes the repulsive force between the iron nuclei and the core compresses, however, shortly thereafter it recoils. The recoil results in a shock wave that moves explosively through space. As the shock wave encounters the outer layer of the star, material is fused together creating new elements and radioactive isotopes. The image below shows the remnants of the supernova with the red color denoting the electrons that are combining with protons to form hydrogen and the blue color denoting electrons moving around the magnetic field. At the center of the nebula lies the remnant of the supernova: a pulsar, a rotating neutron star. The Crab Nebula is so energetic that it emits every known type of light, making it a wonder to observe and study.
