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We present new radio measurements of the expansion rate of the Crab nebula'ssynchrotron nebula over a ~30-yr period. We find a convergence date for theradio synchrotron nebula of CE 1255 +- 27. We also re-evaluated the expansionrate of the optical line emitting filaments, and we show that the traditionalestimates of their convergence dates are slightly biased. Using an un-biasedBayesian analysis, we find a convergence date for the filaments of CE 1091 +-34 (~40 yr earlier than previous estimates). Our results show that both thesynchrotron nebula and the optical line-emitting filaments have beenaccelerated since the explosion in CE 1054, but that the synchrotron nebula hasbeen relatively strongly accelerated, while the optical filaments have beenonly slightly accelerated. The finding that the synchrotron emission expandsmore rapidly than the filaments supports the picture that the latter are theresult of the Rayleigh-Taylor instability at the interface between thepulsar-wind nebula and the surrounding freely-expanding supernova ejecta, andrules out models where the pulsar wind bubble is interacting directly with thepre-supernova wind of the Crab's progenitor.

New expansion rate measurements of the Crab Nebula in radio and optical