From Wikipedia, the free encyclopedia:
"The
Crescent Nebula (also known as
NGC 6888,
Caldwell 27,
Sharpless 105) is an
emission nebula in the constellation
Cygnus, about 5000
light-years away from
Earth. It was discovered by
William Herschel in 1792. It is formed by the fast
stellar wind from the
Wolf-Rayet starWR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a
red giant around 250,000 to 400,000 years ago. The result of the collision is a shell and two
shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to
X-ray-emitting temperatures.
The
Soap Bubble Nebula, or
PN G75.5+1.7, is a
planetary nebula in the constellation
Cygnus, near the
Crescent Nebula (NGC 6888 ). It was discovered by amateur astronomer Dave Jurasevich using an Astro-Physics 160 mm refractor telescope with which he imaged the nebula on June 19, 2007 and on July 6, 2008. The nebula was later independently noted and reported to the
International Astronomical Union by Keith. B. Quattrocchi and Mel Helm who imaged PN G75.5+1.7 on July 17, 2008."
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