T Tauri stars: from mystery to magnetospheric accretion

摘要

This is a selective historical overview of the process in understanding T Tauri spectra.Originally they were understood to be very young, but the physical conditions (or even geometry)of the material on the star and in its surroundings were mysterious. The origin and meaningof the emission lines was largely unknown. Today we have a detailed consensus of what ishappening near and on these newly forming stars. They are very magnetically active, and thestellar field is strong and extensive enough to control both the final accretion onto the star andthe launching of outflows which solve the angular momentum problem during formation. Muchof this consensus has emerged from spectral information, but much remains to be learned. Ihighlight some of the seminal breakthroughs that have led to the current picture. There arevery complex and time-variable components to the entire physical system that constitutes a TTauri star, and spectral information at various wavelengths and resolutions is crucial to makingfurther progress.