nebulas

=** Nebulae **=
 * A nebula is an intersteller cloud of dust composed of many ionized gases including hydrogen and helium. **

= History of Nebulae =

Around 150 AD it was recorded that five stars became nebulous as recorded by Claudius Ptolemaeus. Although this was recorded, the first true nebula was not discovered until 964 by Persian astronomer, Abdal-Rahman al-Sufi. He noticed that a nebula was distinct from a star cluster. He noted a small cloud where the Andromeda Galaxy is located. Also he cataloged the Omicron Velorum star cluster as a "nebulous star" and other nebulous objects, like Brocchi's Cluster. Along with other star discoveries, the supernova that created the Crab Nebula was discovered in 1054.

By 1715 six nebulae have been found as published by Edmund Halley. This number steadily grew throughout the century. In 1753 Nicolas Louis de Lacaille cataloged 42 nebulae. Then Charles Messier compiled a catalog of 103 nebulae (currently known as Messier objects, wich include what are now known as galaxies) by 1781. This number constantly grew and deminished. 510 Nebulae were cataloged in 1802. Soon to be discovered was the fact that these nebulae were merely unresolved clusters of stars. In 1864 William Huggins examined the spectra of about 70 nebulae. He then found that nearly 1/3 of them had the obsorption spectra of a gas. The rest showed a continuos spectrum and were thought to consist of a mass of star.(wikipedia 2012) In 1912 another catagory was added by Vesto Slipher. He discovered that the nebula radiates by reflected star light.

=**Formation of Nebulae**= Many nebulae form from the gravitational callapse of gas in the interstellar medium. As the material collapses under the weight, huge stars may form in the center and their ultraviolet radiation ionize the surrounding fas, making it visible at the optical wavelenghts. New stars formed in the nebulas are sometimes known as a young, loose cluster.

= Application of Nebulae = These discoveries lead to more deep space research. They have produced certain types of telescopes and cameras that are specificly made to take pictures of deep space and nebulas. = References =
 * 1) Beiser, A. (1988). //Physical Science (2nd Edition) //. New York, NY: McGraw Hill
 * 2) []. Nebulas. (2012)

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