Galactic Nebula Sh 2-12
H II Region Sharpless 2-12
In 1951 Stewart Sharpless and Donald Osterbrock did a survey for hydrogen emission regions visible on plates taken in the Hα region with the Greenstein-Henyey wide-angle (~140°) camera at Yerkes Observatory. Two new large H II regions were recorded. One was about 10° in length in the ζ Ophiuchi region. [711] In Sharpless' publication of 1953 this nebula was listed as Sh 1-11. [309] In his 1959 publication the same nebula was listed as Sh 2-12. He recorded a diameter of 120 arc minutes and the notes: «Contains cluster NGC 6383.» [310]
Open Clusters
The open cluster NGC 6383 (h 3689) was discovered by John Herschel on 3 August 1834 while sweeping the sky using his 18.3 inch telescope in South Africa. He noted: «A curious cluster consisting of one large star 6.7, and some 15 or 20 small ones 13m clustering close around it.» On a second observation he noted: «A star 7m with a cluster of stars 12 m assembled about it. The great star occupies the centre. A very remarkable object» and [11] NGC 6374 is a duplicate observation, verified by his mention of the bright star. [364]
John Herschel also discovered NGC 6404 (h 4020, GC 4317) on 27 June 1837 and recorded: «Cluster, faint, large, pretty rich, little compressed, stars 13...15» [467]
The open cluster Trumpler 28 was cataloged by Robert. J. Trumpler in 1930 with remark that it was first mentioned by Barnard (Bd. Atl. pl. 2) as a «very loose open cluster, not rich, but regular in outline and structure.» [712]
| Name | Type | RA (J2000.0) |
Dec (J2000.0) |
PM [mas/y] |
Parall. [mas] |
Rvel [km/s] |
z | Size ['] |
Magnitudes | Identifiers |
|---|---|---|---|---|---|---|---|---|---|---|
| NGC 6383 | OpC | 17h 34m 42s | -32° 34' 23" | 2.596 | 0.873 | -1.2 | -0.000004 | 20 × 20 | C 1731-325; Cl VDBH 232; NGC 6383; OCl 1026.0; [KPR2004b] 402; [KPS2012] MWSC 2631; [SC96] GC 103; [SC96] Mis 540 | |
| NGC 6404 | OpC | 17h 39m 40s | -33° 13' 26" | 0.194 | 0.355 | 10.12 | 0.000034 | 5 × 5 | V 10.6 | C 1736-332; Cl VDBH 240; NGC 6404; UBC 567; [KPS2012] MWSC 2658 |
| Tr 28 | OpC | 17h 36m 55s | -32° 28' 08" | -0.851 | 0.678 | -39.396 | -0.000131 | 5 × 5 | C 1733-324; Cl Trumpler 28; Cl VDBH 238; [KPR2004b] 404; [KPS2012] MWSC 2641 |
Dark Nebulae
| Name | Type | RA (J2000.0) |
Dec (J2000.0) |
Size ['] |
Identifiers |
|---|---|---|---|---|---|
| Barnard 273 | DNe | 17h 38m 30s | -33° 20' 00" | 15 × 15 | Barnard 273; [DB2002b] G355.46-1.02 |
| Barnard 275 | DNe | 17h 39m 00s | -32° 19' 00" | 13 × 13 | Barnard 275; TGU H2190 P8; [DB2002b] G356.37-0.57 |
Finder Chart
The nebula Sh 2-12 is located in the constellation Scorpius, roughly 1.5° west of Messier 6. On 14 June it is in opposition to the Sun and culminates at local midnight. The best time to observe is April to August.
