Engraved Hourglass Nebula: Difference between revisions

The '''Engraved Hourglass Nebula''' (also known as '''MyCn 18'''<ref>MyCn stands for Margaret Walton Mayall (My) and Annie Jump Cannon (Cn), their 39-object catalogue was published in 1940 as [http://adsabs.harvard.edu/abs/1940BHarO.913....7M ''New Peculiar Spectra''] in the Harvard College Observatory Bulletin, no. 913; Mayall has a later 139-object catalogue to her name, designated My: [http://adsabs.harvard.edu/abs/1951BHarO.920...32M ''New Peculiar Spectra''], Harvard College Observatory Bulletin, no. 920.</ref>) is a young [[planetary nebula]] situated in the southern constellation [[Musca]] about 8,000 [[light-year]]s away from [[Earth]]. It was discovered by [[Annie Jump Cannon]] and [[Margaret Mayall|Margaret W. Mayall]] during their work on an extended [[Henry Draper Catalogue]] (the catalogue was built between 1918 and 1924). At the time, it was designated simply as a small faint planetary nebula. Much improved telescopes and imaging techniques allowed the hourglass shape of the nebula to be discovered by [[Raghvendra Sahai]] and [[John Trauger]] of the [[Jet Propulsion Laboratory]] on January 18, 1996. It is conjectured that MyCn 18's [[hourglass]] shape is produced by the expansion of a fast [[stellar wind]] within a slowly expanding [[cloud]] which is denser near its equator than its poles. The vivid colours given off by the nebula are the result of different 'shells' of elements being expelled from the dying star, in this case [[Helium]], [[Nitrogen]], [[Oxygen]] and [[Carbon]].