Fortunately for astronomers, this complex is relatively close to us— only about 500 light years away— and is also quite young. This means astronomers can observe it precisely, something they cannot do with more distant clouds. The only other cloud that is so close is the Taurus-Auriga molecular cloud complex, which is much less dense and somewhat older than Rho Oph. Age is important to the study of star formation, since little is known about the order in which stars of different masses form out of a molecular cloud. The star-forming region in this image is estimated to be only a few million years old— very young indeed, when one remembers that our Sun is thought to be 5 billion years old.