Energy Transport

Inside a main-sequence star, energy travels outward through two mechanisms. In the radiative zone, photons creep outward in a slow random walk, scattering off particle after particle. In the convective zone, hot plasma rises, cools, and sinks in giant circulation patterns, much like water boiling in a pot.

The balance between radiative and convective zones depends on mass. Low-mass stars are fully convective — energy churns from core to surface. High-mass stars have convective cores and radiative envelopes. This difference affects how they mix their fuel and ultimately how they die.