Herbig Ae/Be stars
FU Orionis stars
Herbig-Haro objects
T Tauri stars
Stellar evolution
Pre-main sequence stars
Young stellar objects
YSO
YSOs
Protostars
Any star that has evolved past the protostar stage, but has not yet arrived on the main sequence. There is a variety of YSOs depending on their age, mass, and environment, including Herbig stars, T Tauri stars, and, in general, compact infrared sources embedded in molecular clouds.