Sh 2-82
Reflection nebula in the Sagitta constellation
From Wikipedia, the free encyclopedia
Sh 2-82 (also known as the Little Cocoon Nebula or Little Trifid Nebula) is a small H II region and reflection nebula located in the constellation Sagitta. It is an active star-forming region embedded within a dark nebula, featuring a bright red emission component ionized by ultraviolet radiation from a hot young star, contrasted against a hazy blue reflection nebula created by scattered starlight. The nebula's compact, cocoon-like structure, with a flare on one side, makes it a popular target for amateur astronomers and astrophotographers.[2][3] The nebula is ionized by the star HD 231616 (B0.5III).[4][5][6]
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| Nebula | |
|---|---|
Image of Sh 2-82 Nebula | |
| Observation data: epoch | |
| Right ascension | 19h 30m 14.90s[1] |
| Declination | +18° 17′ 30.0″[1] |
| Distance | 3,500 ly (1,100 pc) |
| Constellation | Sagitta |
| Designations | Sh 2-82, LBN 129, DG 159[1] |
Observation and characteristics
The nebula has some informal nicknames, such as Little Cocoon Nebula, which derives from its enveloping reflection component resembling a protective shell around the central emission core, similar to the IC 5146 (Cocoon Nebula), while Little Trifid Nebula draws a comparison to the larger Trifid Nebula (M20) due to its tripartite appearance in deep-sky images, blending emission, reflection, and dark nebula.[7][8]
Sharpless 2-82 is situated near the inner edge of the Vulpecula OB4 stellar association, a group of young, hot stars in the Milky Way's Sagittarius arm. It lies approximately 3,500 light-years from Earth. Astrophotography of Sharpless 2-82 often employs hydrogen-alpha and O-III narrowband imaging to highlight the ionized gas structures, revealing intricate dust lanes and embedded young stellar objects (YSOs).[9][4]
The primary ionizing source is the blue giant star HD 231616 (B0.5III), part of the OB association Vul 0B4, and surrounding the emission nebula is a bluish reflection component, formed when light from nearby stars scatters off dust grains in the foreground dark cloud LDN 727.[10] This creates a hazy halo that flares asymmetrically on one side, giving the cocoon appearance.[9]
See also
- NGC 1624, also known as the 'Little Cocoon Nebula'
- NGC 1579, known as the 'Northern Trifid Nebula'
- Cocoon Nebula
- Trifid Nebula