YOUNG STARS AND THEIR SURROUNDINGS

As stars are created by the gravitational contraction of knots in gian t interstellar clouds, they shed angular momentum and magnetic and gra vitational energy in an interplay of complex circumstellar structures: swirling disks, fast collimated jets, and shock waves in the surround ing cloud. Many of these structures were inferred a decade ago from gr ound-based telescope observations.' The high resolution of the Hubble Space Telescope and other instruments has now revealed these circumste llar regions in great detail, showing features never before imagined. In the Orion Nebula alone, examples of all types of interactions betwe en young stars and their environment can be seen simultaneously, highl ighting circumstellar dynamics in sharp relief in one of astronomy's m ost famous objects.