Crescent-shaped planetary nebula SH2-188 glows in wisps of green in this skywatching image.
Astrophotographer Bill Snyder captured this stunning deep-space image Feb. 22, 2012 at his Home Observatory in Connellsville Pa.
Sh2-188, also referred to as the Dolphin nebula, is approximately 850 light years from Earth in the constellation Cassiopeia. A light-year is the distance light travels in one year, or about 6 trillion miles (10 trillion kilometers).
The unique, crescent shape of the nebula led astronomers to initially believe SH2-188 was the remnant of a supernova. However, SH2-188 was confirmed to be an asymmetrical planetary nebula.
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