Protostars with emission lines as well as absorption lines in their spectra and whose luminosity can change irregularly as they eject material into space are
A) asymptotic giant branch stars.
B) T Tauri stars.
C) red-giant stars.
D) main-sequence stars.

Question

Quizplus · Accepted Answer

Protostars with emission lines and irregular luminosity changes are characteristics of T Tauri stars, which are young, pre-main sequence stars. Asymptotic giant branch stars and red giants are more evolved stars, while main-sequence stars typically do not have emission lines or irregular luminosity changes during their stable phase.

Protostars with Emission Lines as Well as Absorption Lines in Their