Galactic Nebulae NGC 6857 (Sh 2-100) + Sh 2-99
History
On 6 September 1784 William Herschel discovered an object which he classified as «very faint nebula» with the designation III 144. He noted: «Some extremely small stars with nebulosity, irregularly extended. Verified with 240x magnification.» [463] John Herschel made three observation and listed it has h 2062. He noted: «A small bunch of very minute Milky Way stars, so small as almost to look nebulous; north preceding is another.» [466]
In 1946 the German-American astronomer Rudolph Minkowski has identified NGC 6857 (Min 1-98) and the two much fainter preceding nebulae as emission nebulae and concluded they are probably the brightest parts of one very extended, extremley faint nebulosity. [397]
In the 1950-ies the American astronomer Stewart Sharpless discovered two H II regions on the 48 inch Schmidt telescope photo plates of the «Palomar Observatory Sky Survey». In the catalogue of 1959 the nebulae are listed as Sh 2-99 and Sh 2-100. [310]
Physical Properties
| Name | Type | RA (J2000.0) |
Dec (J2000.0) |
Size ['] |
Magnitudes | Identifiers |
|---|---|---|---|---|---|---|
| Sh 2-99 | HII | 20h 00m 53s | +33° 29' 26" | 2.666666746 × 2.666666746 | B 13.79; V 12.86 | GSC 02674-02056; IRAS 19589+3320; LBN 070.13+01.71; LBN 160; PK 069+01 1; PN Kj 1-2; SH 2-99; WSRTGP 1958+3321; [ABB2014] WISE G070.149+01.725; [BNM96] 070.144+1.725; [T70] 29; [TGC96] 1958+3321; [TP72] 75 |
| Sh 2-100 | HII | 20h 01m 45s | +33° 31' 14" | LBN 070.24+01.53; LBN 161; SH 2-100; [T70] 30 | ||
| NGC 6857 | HII | 20h 01m 48s | +33° 31' 33" | 1.766666651 × 1.766666651 | Min 1-98; NGC 6857; PK 070+01 2; PN ARO 196; PN VV 247; PN VV' 523; [ABB2014] WISE G070.280+01.583; [W69] D |
Finder Chart
The two H-II regions Sh 2-99 and Sh 2-100 are located in the constellation Cygnus. On 20 July they are in opposition to the Sun and culminates at local midnight. The best time to observe is March to December, when the constellation is highest at night.
