Galactic Nebula Sh 2-9

Ophiuchus Molecular Cloud
Ophiuchus Molecular Cloud: Star forming region with open cluster Collinder 302 with Ophiuchus molecular cloud (Antares Nebula vdB 107, nebula IC 4603, ρ Ophiuchi nebula IC 4604, nebula IC 4605, Sharpless 2-9, many dark clouds), plus globular clusters M 4 and NGC 6144. North is left; Canon EOS 20Da, zoom lens 131 mm f:5.6 ; 145 min @ ISO 1600; Astrofarm Tivoli, Namibia, 1345 m ü. M.; © 5. 6. 2011 Eduard von Bergen, Hansjörg Wälchli

History

Who first discovered the nebula around the star σ Scorpii is unclear. As early as 1920, Seares and Hubble examined the spectrum of this «nebulous star». [564] In 1955, the Australian astronomer Colin Stanley Gum listed the nebula around σ Scorpii as the 65th object (Gum 65) in his «Survey of Southern HII Regions». [555] In the late 1950s, the American astronomer Stewart Sharpless classified the large nebula Sh 2-9 as an H-II region on the basis of the photographic plates of the «Palomar Observatory Sky Survey». In 1959, he published his discovery in a catalogue along with 313 HII regions. [310]

Physical Properties

Sh 2-9 (Sharpless 2-9) is a reflection and emission nebula around the 2.9 mag bright star σ Scorpii (Al Niyat). The reddish areas consist of ionised hydrogen and are excited to glow by the star's UV radiation. The bluish ones are dust reflecting the star's light. This nebula belongs together with IC 4603, IC 4604, IC 4605 the Antares Nebula vdB 107 and many dark clouds to form a large nebula area, the Ophiuchus Molecular Cloud. Its centre lies about one degree south of the star ρ Ophiuchi, is surrounded by dense dust and is only visible on infrared images.

The Ophiuchus Molecular Cloud, also called the Rho Ophiuchus Cloud, is an area of active star formation that is one of the closest to us, at a distance of only about 407 light years. X-ray and infrared observations have revealed more than 300 young stars within the large cloud at its centre. The age of these stars is estimated to be only 300'000 years - very young compared to the oldest stars in the universe, which are more than twelve billion years old. [460]

Finder Chart

The nebula Sh 2-9 is located in the constellation Scorpius around the 2.9 mag bright star σ Scorpii (Al Niyat). The best time to observe is April to August.

Chart Galactic Nebula Sh 2-9
Galactic Nebula Sh 2-9 in constellation Scorpius. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

More Objects Nearby (±15°)

References

149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
310«A Catalogue of H II Regions» Stewart Sharpless, US Naval Observatory, 1959; DOI:10.1086/190049; Bibcode:1959ApJS....4..257S
460Young Stars in Their Baby Blanket of Dust; nasa.gov/mission_pages/spitzer/multimedia/20080211.html (2021-12-30)
555«A Survey of Southern HII Regions» Gum, Colin S.; Memoirs of the Royal Astronomical Society, Vol. 67, p.155, 1955; Bibcode:1955MmRAS..67..155G
564«The color of the nebulous stars» Seares, F. H. ; Hubble, E. P.; Astrophysical Journal, 52, 8-22 (1920); DOI:10.1086/142555; Bibcode:1920ApJ....52....8S