Solar physics is the branch of astrophysics that specialises in the study of the Sun and stars. These articles cover types of stars, the life cycle of stars, spectroscopy and observations of our Sun.
In astronomy, luminosity is the total amount of energy radiated by a star, galaxy, or another astronomical object per unit time. It is related to the brightness, which is the luminosity of an object in a given spectral region. In SI units luminosity is measured in joules per second or watts.