The enviroments of T Tauri stars

T Tauri stars are probably newly formed stars at a stage when their surroundings have just sufficiently cleared for the stars to be observed optically. The study of these stars should yield valuable clues about the star formation process. Outside of the extended stellar atmosphere is a circumstellar region where the mass loss and radiation from the star interact with the surrounding medium. The circumstellar region is the site of forbidden line emission, H2 line emission, radio emission, infrared emission by dust, and optical polarized radiation. The present investigation has the objective to study the nature of the circumstellar region. The possible dynamics of the region is discussed, taking into account both inflow and outflow of gas from star. The observed radiative phenomena are used to deduce the actual dynamical situation. Attention is given to a model which suggests several possible evolutionary phases for T Tauri stars.