A type of irregularly varying star whose spectrum shows broad and very intense emission lines. T Tauri stars are believed to be very young and have not yet settled onto the main sequence depicted in the Hertzsprung-Russell diagram.
Protostar in the late stages of formation, often exhibiting violent surface activity. T Tauri stars have been observed to brighten noticeably in a short period of time, consistent with the idea of rapid evolution during this final phase of stellar formation.
A young star with a circumstellar disk and a bipolar outflow.