The Crab Nebula , filled with mysterious filaments, is the result of a star that exploded in 1054 AD . 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 , 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 green indicates the electrons are whirling around the magnetic field of the inner nebula .
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