Circumstellar Disks and Envelopes around Young Low-mass Stars

How do stars - like our sun - form? Where do planets comefrom? - In the last years astronomers were able to uncover some of the fundamental processes related to these very questions. It showed that circumstellar disks and envelopes of gas, dust and icesare a natural by product of the formation process of young stars. These objects grow then more massive by accreting material from thedisk, which itself is fed by the envelope in the early phases. Inthe course of several million years, the envelope is dispersed, infall onto the disk comes to a hold, and most matter is eitheraccreted onto the young star or possibly built into planets. In this book, astronomical observations of young low-mass stars are presented. Using data from modern telescopes the surrounding accretion disks and envelopes are investigated, and physical parameters, their possible dust compositions, and ice propertiesare derived. Some of the young stars seem to have masses in the range of only several Jupiter masses and might be among the least massive free-floating objects known today. This book is intended for students in physics or astronomy who are interested in the formation of stars and planets.