A star's core fuses hydrogen, generating outward radiation pressure that balances inward gravity (hydrostatic equilibrium). Higher fusion rate increases luminosity and outward photon flux (glowing particles); orbiting planets trace Keplerian orbits set by the star's mass and the gravity constant.
L ∝ fusion_rate · M^3.5 (mass-luminosity relation, simplified)
Balance = P_radiation / (G·M/r²)
T² ∝ r³ / (G·M) (Kepler's third law)
- Star mass — sets gravitational pull and baseline luminosity via the mass-luminosity relation.
- Fusion rate — throttles core energy generation, driving luminosity and outward photon particles.
- Orbiting bodies — number of planets/bodies orbiting under the star's gravity.
- Gravity strength — scales the effective gravitational constant G, changing orbital speed and radius stability.
Real-world application: this radiation-pressure/gravity balance is what keeps stars stable for billions of years, and what causes a supernova when fusion can no longer hold gravity back.