Crab Nebula, diffuse gaseous nebula in the constellation Taurus; cataloged as NGC 1952 and M1, the first object recorded in Charles Messier's catalog of nonstellar objects (see Messier catalog). It is the remnant of a supernova that was observed in 1054 by Chinese and Arab astronomers to be as bright as Venus; markings in northern New Mexico depict a star near a crescent moon that might be a record of this supernova. Only three other supernovas have been observed in our galaxy since then. The explosion of the Crab Nebula produced a large expanding shell of delicate filaments. The filaments contain ionized gas in which unusually energetic electrons twist through magnetic fields at speeds close to that of light, emitting synchrotron radiation. Although this radiation is what makes supernova remnants visible in radio wavelengths, in this nebula it is so strong that observers can see the filaments through moderate-sized optical telescopes under good conditions. The nebula is also a strong emitter of X rays. At its center is a pulsar, PSR 0531+21, that spins 30 times per second. The youngest pulsar observed, it gives off radiation at radio, optical, ultraviolet, X-ray, and gamma ray wavelengths, as well as electrons that power the synchrotron radiation in the surrounding nebula.
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