Blue Horsehead Nebula (IC 4592)

IC 4592
IC 4592: Reflection nebula in Scorpius (Blue Horsehead Nebula); Borg 90 FL - Fluorite doublet APO refractor, f=360 mm; CANON 6D (Baader modified); Rainbow Astro RST135E harmonic drive mount; 18 x 600 Sec @ 200ISO; Astrofarm Tivoli, Namibia; © April 2024 Hansjörg Wälchli [46]
IC 4592
IC 4592: Blue Horsehead Nebula (IC 4592), Rho Ophiuchi Nebula Complex (IC 4603-04-05-06, Sh 2-9), B 44, M 4, M 80, NGC 6144 and planet Mars (in Sco) and Saturn (in Oph); Carl Zeiss Apo Sonnar T* 135 mm f/2.0 ZE at f/2.8; Canon EOS 6Da; 21x5 min; ISO 800; Namibia, Tivoli Southern Sky Guest Farm, 1360 m ASL; © 29. 8. 2016 Manuel Jung [45]


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]

Revised+Historic NGC/IC Version 22/9, © 2022 Dr. Wolfgang Steinicke [277]
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.

Finder Chart Blue Horsehead Nebula (IC 4592)
Blue Horsehead Nebula (IC 4592) in constellation Scorpius. Charts created using SkySafari 6 Pro and STScI Digitized Sky Survey. Limiting magnitudes: Constellation chart ~6.5 mag, DSS2 close-ups ~20 mag. [149, 160]

Objects Within a Radius of 15°