Wikipedia:Today's featured article/June 15, 2005

The Cat's Eye Nebula is a planetary nebula in the constellation of Draco. Structurally, it is one of the most complex nebulae known, with high resolution Hubble Space Telescope observations revealing remarkable structures such as knots, jets and sinewy arc-like features. It was discovered by William Herschel on February 15, 1786, and was the first planetary nebula whose spectrum was investigated, by the English amateur astronomer William Huggins in 1864. Modern studies reveal several mysteries. The intricacy of the structure may be caused in part by material ejected from a binary central star, but as yet there is no direct evidence that the central star has a companion. Also, measurements of chemical abundances reveal a large discrepancy between two measurement methods, the cause of which is uncertain.

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