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How Astronomers Know — Evidence Lab

Stellar Lifetime from Mass

Estimated time
~30 min
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Learning goals
  • A star's main-sequence lifetime is set by how much fuel it has and how fast it burns that fuel. Both scale with mass, and burning speed wins.
  • HS-ESS1-1 — Students relate stellar mass to lifetime via fusion energy production.
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Question 1 of 3

Using the approximate relation t ≈ 10¹⁰ years × (M/M_sun)^(-2.5), estimate the main-sequence lifetime of a 3 solar-mass star. Give your answer in units of 10⁹ years (Gyr).

The relation combines two ideas: a star's luminosity grows steeply with mass (L ∝ M^3.5), while the fuel supply only grows linearly with mass. So burn rate wins.

Gyr

    Sources