Blue Horsehead Nebula (IC 4592)
History
This nebula was discovered on 23 March 1895 by American astronomer Edward Emerson Barnard on photograph he made with the 6" Willard lens at Lick Observatory. [277]
In 1946 the Swedish astronomer Sven Cederblad published a study of bright diffuse galactic nebulae where he listed this nebula as number 128 (Cederblad 128). [130]
The Canadian astronomer Sidney van den Bergh searched in 1966 the photo plates of the «Palomar Observatory Sky Survey» (POSS) and identified a weak, moderately blue reflection nebulae with radius of 5.7 arcminutes around star BD -19°4333 (ν Scorpii). He listed it as vdB 100 and noted: «BD -19°4332, V=7.3 also involved. Dimensions given are those of the blue portion of nebula. The outer region of the nebula is red due to emission or reflected light from α Sco.» [255]
Physical Properties
IC 4592 is a reflection nebula illuminated by the double or multiple star ν (nu) Scorpii. The star has a visual brightness of 4 mag and is of spectral type B2V. The distance of the star is given with 375 pc. [145]
| Designation | IC 4592 |
| Type | RN+* |
| Right Ascension (J2000.0) | 16h 11m 59.6s |
| Declination (J2000.0) | -19° 27' 35" |
| Diameter | 150 × 60 arcmin |
| Metric Distance | 0.120 kpc |
| Dreyer Description | vL, E, ν2 Scorpii inv |
| Identification, Remarks | LBN 1113; ESO 584-N*6; CED 128 |
Finder Chart
The reflection nebula IC 4592 is located in the constellation Scorpius around the 4 mag star ν Scorpii (Jabbah). The best time to observe is April to August.
