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| The Crab Nebula, M1 or NGC 1952, in the constellation Taurus. My image, data from the Bradford Robotic Telescope. |
The supernova which created 'The Crab' is believed to have occurred in AD 1054, there are records from the the Far East and the Middle East of the appearance of a bright star in that year. At maximum the supernova would have been brighter than any night sky object other than the Moon.
In visible light, the Crab Nebula consists of a broadly oval-shaped mass of filaments, about 6 arcminutes long and 4 arcminutes wide (by comparison, the full moon is 30 arcminutes across) surrounding a diffuse blue central region. In three dimensions, the nebula is thought to be shaped like a prolate spheroid (a rugby ball). The filaments are the remnants of the progenitor star's atmosphere, and consist largely of ionised helium and hydrogen, along with carbon, oxygen, nitrogen, iron, neon and sulfur. The filaments' temperatures are typically between 11,000 and 18,000 K, and their densities are about 1,300 particles per cm3.
In 1968 a pulsar, a fast spinning neutron star, was found within the nebula. At the centre of the Crab Nebula are two faint stars, one of which is the star responsible for the existence of the nebula. It was identified as such in 1942, when Rudolf Minkowski found that its optical spectrum was extremely unusual. The region around the star was found to be a strong source of radio waves in 1949 and X-rays in 1963 and was identified as one of the brightest objects in the sky in gamma rays in 1967. Then, in 1968, the star was found to be emitting its radiation in rapid pulses, becoming one of the first pulsars to be discovered.
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| The Crab Nebula in a wider field and much like the view throgh Olly's ' big Dob' telescope |
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