A colorful orb decorates the region surrounding the bright triple star Rho Ophiuchus. Probably no other region provides such an impressive spectacle of colorful glowing gases juxtaposed with converging dark rivers of thick dust. The area is highlighted by the bright star Antares, a red supergiant 40,000 times more luminous than our sun. The star is immense. With a diameter of 800 million kilometers it is so large that it is one of the few stars with a measurable disk. If placed at the sun its edge would stretch almost to the planet Jupiter. Antares lies embedded in an unusual circumstellar yellow cloud formed by the ionization of the fierce stellar winds blown by the dying star. Antares has a B type companion star only 3 arcseconds away which orbits the larger star every 900 years.
The colorful clouds surrounding Rho Ophiuchus represents the visible counterpart of a much larger but invisible molecular cloud permeating the region and known as the Ophiuchus cloud. This giant molecular cloud is one of the nearest and most studied regions of star formation in the local Milky Way at a distance of about 520 light years. A peculiar feature of the Ophiuchus cloud is the presence of a condensed core with very active star formation. The central core is located in the dark cloud L1688 near the star Rho Ophiuchus. The Ophiuchus cloud lies well above the plane of the galaxy near the border of the Scorpius-Centaurus OB association, the nearest OB association to our sun. It is believed that about 1.5 million years ago a massive star in upper scorpius exploded as a supernova sending a powerful shock wave that now passes through the Ophiuchus cloud triggering star formation in the cloud beginning 1 million years ago and continuing today.