Monday, Jul 1, 2024

IC 4604 (Rho Ophiuchi Nebula) is a large diffuse nebula of 5th magnitude located in the southwestern corner of the constellation Ophiuchus, surrounding the bright multiple star system Rho Ophiuchi. Several regions of bright and dark nebulosity surround this area, which takes its name from Oph. Highlighted by the bright star Antares, the region provides an impressive spectacle of colorful glowing gases, juxtaposed with converging dark rivers of thick dust. Other areas of nebulosity within the region include IC 4603, centered around the star SAO 184376; and IC 4605, around 22 Scorpii. The nebulosity around Antares itself (a Sco) is designated IC 4606. Dark nebulae Barnard 45 and Barnard 42 separate the reflection nebulosity near ? Oph (IC 4603 and IC 4604) from the nebulosity closer to 22 Sco and Antares (IC 4605 and IC 4606). At a distance of some 540 light years, IC 4604 is one of the nearest star-forming regions to the Sun. The colorful clouds surrounding Rho Ophiuchi represent the visible counterpart of a much larger but invisible molecular cloud permeating the region. This Ophiuchus cloud lies well above the plane of the galaxy, near the border of the Scorpius-Centaurus OB association. About 1.5 million years ago, a massive star in upper Scorpius exploded as a supernova, sending a powerful shock wave through the Ophiuchus clouds about 1 million years ago, triggering star formation that is still continuing today.