An Etymological Dictionary of Astronomy and Astrophysics

A complex region of molecular and dust clouds containing emission and reflection nebulae near the star ρ Oph in the constellation → Ophiuchus. It is one of the closest star forming regions, some 400 light-years distant. Recent studies using the latest X-ray and infrared observations reveal more than 300 young stellar objects within the large central cloud. Their median age is only 300,000 years.

See also: Rho, Gk. letter; → Ophiuchus; → cloud.