Detonative expansion of a supernova remnant: The Crab Nebula

A supernova remnant is the resulting nebula of a star burst through a supernova. The accelerative expansion of one of the most famous supernova remnant, the Crab Nebula, is a mystery in dynamics, because an expanding shock wave should decelerate when bumping into the surrounding interstellar medium. Here we show that the strong relativistic pulsar wind bumping into its surrounding nebula induces energy generating processes and initiates a detonation wave that propagates outward to form the outer envelope of the nebula. The resulting detonation wave then provides the needed power to maintain propagation of the nebula envelope. Furthermore, relaxation of the curvature-induced reduction of the propagation velocity to approach the planar state of Chapman-Jouguet propagation explains the observed accelerative expansion. Additional applications of the conventional combustion theory to various astrophysical phenomena are expected to yield rich insight into the underlying fluid dynamics and reactions in the extraterrestrial media.