George H. Herbig
It is fitting that, in opening this Symposium with consideration of the T Tauri stars, we note that this month marks the tenth anniversary of the September 1945 issue of the Astrophysical Journal, in which appeared the remerkable pioneering paper by Alfred H. Joy that initiated the study of emission-line stars associated with nebulosity. This contribution opened a new aproach to the study of the relationship of stars to their environment. Today, ten years later, the T Tauri stars and their interaction with nebualr material form a topic whose significance we may not fully appreciate and whose opportunities have been as yet only superficially exploited.
In the decade that has passed since the appearance of Joy's 1945 paper, a great deal of work has been done in this field (most of it, I should remark, by astronomers who are to participate in this Symposium). Rather than attempting to summarize these ten years of progress, I wish to do only two things: first, to present an assessment of the problem of the nature of T Tauri stars as it stands today, and second, to discuss some evidence that may bear on the question of the origin of these objects. If a satisfactory solution to even one of these problems can be found, it will then be possible to look for a deeper significance in the instability of the T Tauri stars.