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Crescent Nebula

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Crescent Nebula
Emission nebula
The Crescent Nebula, as taken by anamateur astronomer
Observation data: J2000.0epoch
Right ascension20h12m7s[1]
Declination+38° 21.3′[1]
Distance5,000ly
Apparent magnitude(V)+7.4
Apparent dimensions (V)18′ × 12′
ConstellationCygnus
DesignationsNGC6888,[1]Sharpless105,Caldwell27
See also:Lists of nebulae
Crescent Nebula (Caldwell27) captured by David Rousseau from an urban location in Québec, Canada using Ha and OIII narrowband filters.

TheCrescent Nebula(also known asNGC 6888,Caldwell 27,Sharpless 105) is anemission nebulain the constellationCygnus,about 5000light-yearsaway fromEarth.It was discovered byWilliam Herschelin 1792.[2]It is formed by the faststellar windfrom theWolf-Rayet starWR 136(HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became ared giantaround 250,000[3]to 400,000[citation needed]years ago. The result of the collision is a shell and twoshock waves,one moving outward and one moving inward. The inward moving shock wave heats the stellar wind toX-ray-emitting temperatures.

The Crescent Nebula is a rather small object located about 2 degrees Southwest ofSadr.While considered bright by astronomical imaging standards, visually it is relatively faint. For most telescopes it requires aUHC or OIII filterto see. Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity. Larger telescopes (20 cm or more) reveal the crescent or aEurosign shape which makes some to call it the "Euro sign nebula".

  • Crescent Nebula NGC 68888 Imaged by Don Christopher Deaver
    NGC 6888 in Hydrogen and Oxygen Light. HOO Palette. Imaged by Don Christopher Deaver
  • Crescent Nebula in H-alpha and OIII. Imaged with a 715mm focal length telescope. The hydrogen gas is red. The oxygen is blue.
    Crescent Nebula in H-alpha and OIII. Imaged with a 715mm focal length telescope. The hydrogen gas is red. The oxygen is blue.
  • Image of NGC 6888 using H-alpha filter.
    Image ofNGC 6888using H-alpha filter.
  • Picture of NGC 6888 captured in narrowband by amateur astronomer Luca Moretti
    Picture ofNGC 6888captured in narrowband by amateur astronomer Luca Moretti
  • NGC 6888 imaged in 3 nm hydrogen-alpha and oxygen-III narrowband at 2800mm focal length by amateur astronomer Patrick Hsieh.
    NGC 6888 imaged in 3 nm hydrogen-alpha and oxygen-III narrowband at 2800mm focal length by amateur astronomer Patrick Hsieh.

See also

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References

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  1. ^abc"NGC 6888".SIMBAD.Centre de données astronomiques de Strasbourg.Retrieved2007-04-23.
  2. ^Erdmann, Robert."NGC 6888".The NGC/IC Project.Archived fromthe originalon 2012-05-20.
  3. ^"WR 136".jumk.de.Retrieved25 March2018.
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