Galactic Nebula Sh 2-54
History
On 15 July 1784 William Herschel discovered the open cluster NGC 6604 which he listed it as VIII 15 with the notes: «A coarsely scattered cluster of stars.» [463]
In the 1950-ies the American astronomer Stewart Sharpless discovered the H II region on the 48 inch Schmidt telescope photo plates of the «Palomar Observatory Sky Survey». In his 1953 publication the nebula is listed as Sh 1-41 with the notes: «Very bright central portion; cluster.» [309] In his updated catalogue of 1959 the nebula is listed as Sh 2-54 with the notes: «Part of II Ser association. Contains cluster NGC 6604.» [310]
In 1955 Colin S. Gum from the Commonwealth Observatory in Canberra did a survey of H-II regions and identified this nebula as two parts: Stromlo 84 (today Gum 84) with an angular dimension of 70 x 30 arc minutes containing cluster NGC 6604 and Stromlo 85 (today Gum 85) with an angular dimension of 4 arc minutes. For the second one he noted: «Almost lies within Stromlo 84 but this is probably a case of alignment. Stromlo 85 is small, round and compact compared to the more scattered Stromlo 84. They are probably separate objects.» [555]
Physical Properties
| Name | Type | RA (J2000.0) |
Dec (J2000.0) |
PM [mas/y] |
Parall. [mas] |
Rvel [km/s] |
z | Identifiers |
|---|---|---|---|---|---|---|---|---|
| Sh 2-54 | HII | 18h 17m 52s | -11° 40' 58" | IRAS 18150-1142; LBN 018.45+01.87; LBN 72; Mol 46; SH 2-54 | ||||
| NGC 6604 | OpC | 18h 18m 03s | -12° 14' 30" | -0.66 | 0.454 | 16.5 | 0.000055 | C 1815-122; CTB 50; Cl Collinder 373; Cl Mrk 39; LMH 24; MM 23; NGC 6604; NRL 17; OCISM 11; OCl 56; Villafranca O-035; [KPR2004b] 439; [KPS2012] MWSC 2878 |
Finder Chart
The H-II region Sh 2-54 is located in the constellation Serpens. On 24 June it is in opposition to the Sun and culminates at local midnight. The best time to observe is March to September, when the constellation is highest at night.
