Crab Nebula The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus. Corresponding to a bright supernova recorded by Chinese astronomers in 1054, the nebula was observed later by English astronomer John Bevis in 1731. At an apparent magnitude of 8.4, comparable to that of the largest moon of Saturn, it is not visible to the naked eye but can be made out using binoculars under favourable conditions. 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. Located at a distance of about 6,500 light-years (2 kpc) from Earth, the nebula has a diameter of 11 light years (3.4 pc, corresponding to an apparent diameter of some 7 arc minutes) and expands at a rate of about 1,500 kilometers per second (0.5% c). It is part of the Perseus Arm of the Milky Way galaxy. At the center of the nebula lies the Crab Pulsar, a neutron star 28–30 km across with a spin rate of 30.2 times per second, which emits pulses of radiation from gamma rays to radio waves. The nebula was the first astronomical object identified with a historical supernova explosion. The nebula acts as a source of radiation for studying celestial bodies that occult it. In the 1950s and 1960s, the Suns corona was mapped from observations of the Crabs radio waves passing through it, and in 2003, the thickness of the atmosphere of Saturns moon Titan was measured as it blocked out X-rays from the nebula. Image Credit: NASA/HubbleSpace >>>
Posted on: Sat, 12 Jul 2014 06:44:55 +0000
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