Understanding star color & luminosity
Explore how a star’s temperature and radius change its color, peak wavelength, and luminosity.
The idea behind it
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.
The relationship to remember
L / L☉ = 1² × (5,772 / 5772)⁴ = 1. Wien peak = 2,897,772 / 5,772 = 502.04 nm.
Make your own discovery
Keep the radius fixed and double the temperature. Luminosity increases sixteenfold.
Try the interactive lab ↗What this model leaves out
Stars are approximated as blackbodies. Display colors are illustrative, not calibrated spectra. Radius is shown with a compressed visual scale.
Check your understanding
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.
Continue with the formula reference or test yourself in space practice.