What determines a star's luminosity?

Primarily its mass and evolutionary stage. More massive stars are much more luminous.

Why use M_sun = 4.83?

That is the Sun's absolute visual magnitude. For bolometric calculations, use M_bol,sun = 4.74.

From about 10^-4 L_sun (faint red dwarfs) to over 10^6 L_sun (the most luminous supergiants).

Calculate a star's luminosity from its absolute magnitude: L/L_sun = 10^((M_sun - M_star) / 2.5).

Absolute Magnitude

Luminosity (L_sun)

85.5067 L_sun

Luminosity (W)32,731,953,769,225,675,000,000,000,000.000 W

Luminosity (L_sun) vs Absolute Magnitude

L / L_sun = 10^((M_sun - M_star) / 2.5)

where M_sun = 4.83 (visual). A star 5 magnitudes brighter than the Sun is 100 times as luminous.

A star with M = 0.

Find absolute magnitude from apparent and distance.

Compute luminosity from temperature and radius.

Estimate luminosity from stellar mass.