Sh2-11 — Emission Nebula in Scutum
RA/Dec (J2000): 18h 08m, −19° 30′ (approx.)
Catalogue: Sharpless 2-11, diffuse emission nebula in Scutum.
Historical Overview
Sharpless 2-11 (Sh2-11) is part of the Sharpless catalog of H II regions compiled by Stewart Sharpless in 1959, which extended his earlier 1953 list of nebulae (Sharpless 1959). Unlike the bright showpiece nebulae of Orion or Sagittarius, Sh2-11 is a faint extended emission region ionized by hot OB stars.
Early surveys using wide-field photographic plates noted the region’s diffuse glow, but it remained obscure due to its low surface brightness. In recent decades, narrowband astrophotography has brought Sh2-11 to prominence among amateurs. Its hydrogen-alpha emission outlines star-forming gas clouds in the Milky Way’s Scutum Arm.
Infrared surveys (e.g., Spitzer/GLIMPSE) have revealed embedded young stellar objects within Sh2-11, confirming it as an active star-forming complex (Churchwell et al. 2009).
Key Facts
- Type: Emission nebula (H II region).
- Distance: ~5,500 light-years (estimated).
- Size: ~70 arcminutes across.
- Visibility: Very faint; best in H-alpha or narrowband imaging.
- Scientific importance: Star-forming region in the Scutum Arm of the Milky Way.
References
Churchwell, E. et al. (2009). The Spitzer/GLIMPSE Surveys: A New View of the Milky Way. PASP, 121, 213.
Sharpless, S. (1959). A Catalogue of H II Regions. ApJS, 4, 257.
Sharpless, S. (1953). Emission Nebulae in the Milky Way. ApJ, 118, 362.