Habitable Zone Map (2D)

This 2D top-down simulator lets you dial a star's mass from a dim red dwarf to a hot blue-white star and watch its habitable zone — the annulus where a rocky planet could keep liquid water — shrink close and inward or spread out and widen, following the real relation that luminosity scales roughly with mass to the 3.5 power and zone distance scales with the square root of luminosity. Slide the test planet's orbital distance to see it turn red (too hot, water boils away), green (habitable), or blue (too cold, water freezes), with live readouts of the star's spectral class, temperature, luminosity, and the zone's inner and outer boundaries in astronomical units.