Star color & luminosity
See how a star’s temperature and size set its color, peak wavelength (Wien’s law) and luminosity (Stefan–Boltzmann law). The Sun: 5,772 K, peak near 502 nm.
Your experiment
How it works
Temperature strongly affects emitted power per unit area. A large, cool star can be more luminous than a small, hot star because it has more radiating surface. Wien’s law relates temperature to the wavelength of peak emission.
Star Color, Temperature & Luminosity Explained ↗About this model
Stars are approximated as blackbodies. Display colors are illustrative, not calibrated spectra. Radius is shown with a compressed visual scale.
Key formulas
| Quantity | Formula | Note or example |
|---|---|---|
| Luminosity (Stefan–Boltzmann) | L / L☉ = (R / R☉)² × (T / 5772 K)⁴ | Radius and temperature relative to the Sun |
| Wien’s displacement law | λ_peak = 2,897,772 nm·K ÷ T | Hotter stars peak at shorter wavelengths |
Worked examples
Each row uses one of this lab’s presets and the same model as the interactive tool.
| Example | Luminosity | Peak wavelength | Apparent color |
|---|---|---|---|
| Sun-like | 1 Sun | 502 nm | Yellow-white |
| Cool dwarf | 0.00292 Suns | 966 nm | Orange-red |
| Hot star | 1,140 Suns | 193 nm | Blue-white |
| Sirius A | 25.72 Suns | 292 nm | White |
| Red giant | 216.32 Suns | 828 nm | Orange-red |
Star color & luminosity: common questions
Are blue stars hotter than red stars?
Yes. A hotter blackbody emits relatively more short-wavelength light, shifting its appearance toward blue-white.
Does a brighter-looking star emit more light?
Not necessarily. Apparent brightness also depends on distance and any intervening dust.
What color is the Sun?
The Sun emits most strongly near 500 nm, but its light mixes all visible colors and looks white from space. It appears yellow or orange near the horizon because the atmosphere scatters blue light out of the beam.
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