Stellar Lifetime

Luminosity is the total power output of a star. Power is the rate of producing energy or the rate of using energy. The source of energy in a star is the conversion of mass into energy. Using Einstein’s equation,

Therefore, luminosity is proportional to the mass divided by the lifetime. Using units of solar luminosity and solar mass, and the lifetime of our sun (10 billion years):

in billions of years. The mass-luminosity relation shows that luminosity is proportional to the mass raised to the 3.5 power. Lifetime then is proportional to one over mass raised to the 2.5 power.

in billions of years (M in units of solar mass)

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