Stefan-Boltzmann Constant

Relates a blackbody's temperature to its total radiated power, governing stellar luminosity.

Specifications & Metrics

symbol

σ

status

Exact — derived from defining constants

value

5.670374419 × 10⁻⁸ W·m⁻²·K⁻⁴

Relative Scale in Constants

Core Principles & Analysis

• A blackbody radiates σT⁴ watts per square metre — Stefan's 1879 law, derived by Boltzmann in 1884.
• Derived exactly as 2π⁵k_B⁴/15h³c², so the 2019 redefinition fixed it too.
• Balancing absorbed sunlight against σT⁴ emission gives a planet's equilibrium temperature.

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