Crab Nebula (M1)

In the year 1054 a new bright star was observed in the constellation Taurus. It was bright enough to be visible in daylight for a month before slowly fading from view. It has been subsequently identified as the supernova explosion which ended the life of a star about 6,500 light-years from Earth. The glowing gas remnants of that explosion form the Crab Nebula, named after the telescopic impression of its 1731 discoverer John Bevis, an English doctor, astronomer, and electrical engineer. It was later rediscovered by Charles Messier and became the first entry in his list of fuzzy comet-like objects (M1).

The explosion created a new object, a neutron star, from the remaining stellar material. The M1 neutron star is only 12 miles in diameter with a mass roughly twice that of the sun. Neutron stars have the density of atomic nuclei. A teaspoon of neutron star material would have a mass of about 2 billion tons.

The M1 neutron star is among a small fraction of neutron stars that are pulsars. These objects pulse enormous amount of radiation at regular intervals. The Crab pulsar emits a burst of light across the electromagnetic spectrum 30 times a second. Pulsars have strong magnetic poles that are misaligned with their rotational axis (as does Earth). The radiation is beamed from ionized particles spiraling at near light-speed around the intense magnetic field at the poles, creating a light-house effect. The radiated energy causes pulsars to very gradually slow their rotation.

The interstellar Pioneer and Voyager spacecrafts carried plaques which showed the frequency and direction of 15 pulsars relative to the sun. This would enable an intercepting galactic civilization to determine the time and place from which the crafts were launched. The Crab pulsar did not make the cut to be included on the list for the plaques.