The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus. It is not, as its name might suggest, in Cancer. The now-current name is due to William Parsons, 3rd Earl of Rosse, who observed the object in 1840 using a 36-inch telescope and produced a drawing that looked somewhat like a crab.[5] Corresponding to a bright supernova recorded by Chinese astronomers in 1054, the nebula was observed later by English astronomer John Bevis in 1731. The nebula was the first astronomical object identified with a historical supernova explosion.

At an apparent magnitude of 8.4, comparable to that of Saturn's moon Titan, it is not visible to the naked eye but can be made out using binoculars under favourable conditions. The nebula lies in the Perseus Arm of the Milky Way galaxy, at a distance of about 2.0 kiloparsecs (6,500 ly) from Earth. It has a diameter of 3.4 parsecs (11 ly), corresponding to an apparent diameter of some 7 arcminutes, and is expanding at a rate of about 1,500 kilometres per second (930 mi/s), or 0.5% c.

At the center of the nebula lies the Crab Pulsar, a neutron star 28–30 kilometres (17–19 mi) across with a spin rate of 30.2 times per second,[6] which emits pulses of radiation from gamma rays to radio waves. At X-ray and gamma ray energies above 30 keV, the Crab is generally the strongest persistent source in the sky, with measured flux extending to above 10 TeV. The nebula's radiation allows for the detailed studying of celestial bodies that occult it. In the 1950s and 1960s, the Sun's corona was mapped from observations of the Crab's radio waves passing through it, and in 2003, the thickness of the atmosphere of Saturn's moon Titan was measured as it blocked out X-rays from the nebula.

Crab Nebula in Science FictionEdit

In the Doctor Who universeEdit

The Crab Nebula was a nebula remnant of a supernova. It was created by the Uxarieans by detonating a star with their Doomsday Weapon. (TV: Colony in Space) This was believed to have occurred during the Millennium War circa 150 million BC. (PROSE: The Quantum Archangel)

The planet Wengrol was located in the Crab Nebula (PROSE: The Sons of the Crab), as was the planet Tora. (COMIC: The Enlightenment of Ly-Chee the Wise)

During a visit to 1980s Blackpool, the Sixth Doctor said that a replica of the town was being built on the rim of the Crab Nebula, but they had gotten the design concept wrong, as it was being built for a purpose rather than for frivolity. (PROSE: The Nightmare Fair/AUDIO: The Nightmare Fair)

In the 51st century, humanity relocated to the Crab Nebula after Earth was ruined by solar flares. (COMIC: The Keep)

The Tenth Doctor took Grayla to either the Crab Nebula or the Horsehead Nebula. (COMIC: The Whispering Gallery)

In the Trinity UniverseEdit

The Crab Nebula is the location of the former Karroo Mining Colony that exsited breifly from 2109 to 2113.

In other Science FictionEdit

"First Contact" (1945), novelette by Murray Leinster published in Astounding Science Fiction. In this puzzle story, a human exploration vessel encounters a like alien craft in the vicinity of the Crab Nebula. Neither ship knows the location or even the direction of the other's home planet, but they can be sure it is far away from the recently (in cosmic terms) sterilized neighborhood of the Crab. When communication is established, the two crews realize that in spite of their rough parity, their technologies have developed along very different lines, and they have much of value to learn from each other. If the parties exchange knowledge and part peaceably, the civilization of each stands to be immensely enriched—at the risk of exposing the location of its homeworld to the others' unguessable tracking capabilities and ultimately unknowable intentions. From the point of view of either side, the situation presents a form of Pascal's Wager: No matter how great the finite benefit, and no matter how slight the probability that trust in the strangers might be misplaced, since the penalty for being wrong would be unlimited catastrophe, the mathematical expected value of the cooperative option is - . The rational course for each side is to attempt to destroy the other. Happily, this turns out to be unnecessary as an ingenious nonviolent solution to the conundrum is contrived.

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