Crescent Nebula
Template:Short descriptionTemplate:Infobox nebula 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.[1] It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 years ago[2]. 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.
Visibility
The Crescent Nebula is a rather small object located about 2 degrees Southwest of Sadr. While considered bright by astronomical imaging standards, visually it is relatively faint. For most telescopes it requires a UHC or OIII filter to see. Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity. With higher magnification, it has been reported to have a resemblance to a Euro sign shape leading to a nickname the "Euro Sign Nebula."[3]
Gallery
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NGC 6888 in Hydrogen and Oxygen Light. HOO Palette. Imaged by Don Christopher Deaver
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Crescent Nebula in H-alpha and OIII. Imaged with a 715mm focal length telescope. The hydrogen gas is red. The oxygen is blue.
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Image of NGC 6888 using H-alpha filter.
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Picture of NGC 6888 captured in narrowband by amateur astronomer Luca Moretti
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NGC 6888 imaged in 3 nm hydrogen-alpha and oxygen-III narrowband at 2800mm focal length by amateur astronomer Patrick Hsieh.
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Crescent Nebula (Caldwell27) was captured by David Rousseau from an urban location in Québec, Canada, using Ha and OIII narrowband filters.
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The Crescent Nebula, as taken by an amateur astronomer
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NGC 6888 - The Crescent Nebula, wide field in HOO.
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See also
References
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External links
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