Stellar Luminosity Calculator: Star Brightness a...
Calculate a star's luminosity from its radius and surface temperature using the Stefan-Boltzmann law. Compare stars to the Sun and explore the Hertzsprung-Russell diagram.
What is Stellar Luminosity?
A star's luminosity (L) is the total power it radiates into space. It depends on the star's surface area (proportional to R²) and surface temperature (T⁴ by the Stefan-Boltzmann law). Luminosity is the intrinsic brightness of a star — distinct from apparent magnitude which depends on distance.
⭐ Stellar Luminosity Calculator
Free calculator for instant results.
📐 Formula
L = 4πR² × σT⁴
σ = Stefan-Boltzmann constant = 5.67×10⁻⁸ W/(m²·K⁴). R = stellar radius (m), T = surface temperature (K). Often expressed relative to the Sun: L/L☉.
📝 Worked Example
Star: R = 2R☉, T = 1.2T☉ (T☉ = 5778 K):
L/L☉ = (R/R☉)² × (T/T☉)⁴ = 4 × (1.2)⁴ = 4 × 2.07 = 8.3 L☉
The star is 8.3 times more luminous than the Sun.
📝 How to Use
❓ FAQ
What is the most luminous type of star?
Hypergiants (e.g., R136a1): up to ~10⁷ L☉. Compare to the Sun (1 L☉), red dwarfs (~0.001 L☉), and white dwarfs (<0.01 L☉).
What is the Hertzsprung-Russell diagram?
A plot of luminosity vs surface temperature for stars. It reveals stellar evolution — 90% of stars fall on the "main sequence" diagonal band.
Veer Kumavat
Founder & AuthorVeer is a 14-year-old student from Nashik, Maharashtra, who built SciFi Calculators to help students worldwide master STEM subjects. He is passionate about making complex science and math problems accessible through intuitive digital tools.