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The Incredible Expanding Cat
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| Title |
The Incredible Expanding Cat's Eye |
| Explanation |
Watch closely. As this animation blinks between two Hubble Space Telescope images [ http://aries.usno.navy.mil:80/ad_home/pne/ ] of NGC 6543 - the first from 1994 and the second from 1997 - the intricate filaments of this nebula are seen to shift. The shift is due to the actual expansion of this gaseous shroud shed by a dying star [ http://oposite.stsci.edu/pubinfo/pr/97/38.html ]! NGC 6543 is more popularly [ http://oposite.stsci.edu/pubinfo/pr/95/01.html ] known as the Cat's Eye [ http://antwrp.gsfc.nasa.gov/apod/ap981101.html ] Nebula. Classified as [ http://www.seds.org/billa/twn/types.html ] a "planetary nebula", its complex, interwoven shells of expanding gas [ http://www.astro.washington.edu/balick/WFPC2/ ] have been castoff by the central star as it evolves from a red giant to its final white dwarf phase. The planetary nebula phase of a star's life is known to be relatively brief, lasting 10,000 years or so. In fact, combined with other data [ http://xxx.lanl.gov/abs/astro-ph/9907313 ], this nebula's detectable shift over a three year period allows the expansion age of its bright inner shells to be estimated at only around 1,000 years while its distance can be gauged at about 3,000 light-years. |
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