M 1, the Crab Nebula (so named as it appeared to 19th century astronomers to resemble a crab claw) was the first nebula identified as a supernova remnant. Edwin Hubble was the first to hypothesize that this was the case in 1928, and in 1937 Nicholas Mayall of Lick Observatory provided spectroscopic proof – measurement of its rapid expansion – that Hubble was right.

Calculating the nebula’s expansion of 1,500 kilometers per second backwards showed that it had originated about 900 years earlier.

In the same period, astronomers searching ancient Chinese, Japanese and Islamic records of stellar observations pinned down the date of the supernova to July or August 1054. Chinese records refined the first observation to 4 July 1054 (or, as Americans would later declare for unrelated reasons, Happy 4th of July!)

Ancestral Puebloans at Chaco Canyon in New Mexico appear to have seen and recorded the supernova in a distinctive pictograph. One of the mysteries of astronomical history is the lack of any record of observation of the supernova from Europe, an absence possibly due to prolonged cloudy weather.

In 1967, Jocelyn Bell Burnell and Anthony Hewish discovered pulsars, quickly identified as rotating neutron stars. A year later, the Italian astrophysicist Franco Pacini predicted the existence of a pulsar in the Crab nebula, which was soon confirmed. Knowing its age almost to the day enabled astronomers to calculate the basic properties and evolution of a neutron star.

This one has the approximate mass of the Sun but is only about 30 km across, which means a small match-box quantity would weigh as much as half a cubic kilometer of the Earth’s crust.

Much of the Crab Nebula’s light is generated by synchrotron radiation, as correctly supposed in 1953 by the Russian astronomer Iosif Shklovsky, as electrons in the nebula whirl in the pulsar’s magnetic field at up to half the speed of light. The rotating pulsar itself flashes a beam in the direction of Earth about 30 times per second.

Image reprocessed from November 11, 2010 data.

A line in version B points to what I believe is the neutron star. Please advise if I’m wrong.

CS, Bob