Astronomy

Crab Nebula Discovery



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The Crab Nebula is a bright nebula observed by the Hubble space telescope. John Bevis was an English doctor and astronomer who first discovered the Crab Nebula in 1731. French astronomer Charles Messier independently rediscovered it in 1758. It is believed that the Crab Nebula is the remnants of a supernova that was first seen on Earth in 1054. This event was observed in the Middle and Far East by various groups of astronomers. There is also evidence that it was observed in the U.S. as well. Located in the Milky Way galaxy, it is approximately 6,500 light-years from earth. At the center of the nebula are two faint stars, one of which actually powers the nebula.

John Bevis was born November 10, 1695 in Old Sarum, Wiltshire, England. A physician and an astronomer, Bevis put together a catalogue of stars from work in his observatory in Stock Newington, Middlesex. Charles Messier, in 1758, made an independent rediscovery of the same nebula. But in June of 1771 Bevis sent Messier a letter informing him that he had discovered the nebula some 27 years earlier. Even though John Bevis is credited with the discovery of the Crab Nebula the exploding star, or supernova, whose remnants make up the Crab Nebula was actually first observed in 1054. Chinese and Japanese astronomers recorded what some called, "a guest star in the sky". When the supernova first appeared it could be seen with the naked eye during the day for about 23 days. It could be seen at night for about 650 days. This supernova, also called SN-1054, was observed by Arab and Persian astronomers as well. Evidence shows that Native Americans in the southwestern United States recorded this event. An example of this is an Anasazi cliff painting. There is also a possible mention of the supernova in Irish folklore.

To get a view of the Crab Nebula you have to look for the constellation Taurus. It is located in the constellation Taurus. The Crab Nebula is one of the brightest and most observed objects in the universe. Roughly 12 light-years in diameter, the nebula is constantly expanding. Since the nebula is around 6500 light-years away, it is estimated that the supernova creating the nebula happened around 5500 BC. This type of nebula is a pulsar wind nebula. It is powered by a pulsar (neutron star) located at its center that is emitting x-rays, gamma-rays, and radio waves. The speed at which this star is turning causes the emission of the radiation to burning brightly allowing it to be observed in all of the electromagnetic spectrum. This pulsar rotates 33 times per second. It is more massive than the sun but only about 15 miles across producing energy over a 120,000 times faster than the sun. The X-ray waves emitted from the Crab pulsar are a standard by which other X-rays are measured.

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