IC 4604, Rho Ophiuchi Nebula
The reflection nebula IC 4604 (LBN 1111) belongs together with IC 4603, IC 4605, the Antares nebula vdB 107, Sharpless 2-9 and many dark clouds to a large area of nebula, the Ophiuchus Molecular Cloud. Its center is about one degree south of the star ρ Ophiuchi, is surrounded by dense dust and is only visible in infrared images. The IC numbers were discovered in 1882 by the American astronomer Edward Barnard, who also recorded the dark clouds B 42, B 44 and B 45. [196, 239, 270, 277]
The Ophiuchus Molecular Cloud, also called Rho Ophiuchus Cloud, is an area with active star formation, which is one of the closest to us at a distance of only about 407 light years. X-ray and infrared observations revealed more than 300 young stars within the large cloud in the center. The age of these stars is estimated to be only 300,000 years - very young compared to the oldest stars in the universe, which are more than twelve billion years old. 
The nebula IC 4604 is located in the constellation Ophiuchus (Serpent Bearer) and as the name «Rho Ophiuchi nebula» suggests at the 5 mag star ρ Ophiuchi, around three degrees north of the bright star Antares (α Scorpii) in the constellation Scorpius (Scorpio). The best observation time is April to August.