Stellar Interiors & Energy Transport: Structures & Vocabulary

A star's interior is organized by the competition among gravity, nuclear energy generation, opacity, and energy transport. Energy produced in hot central regions reaches the surface mainly through radiation or convection, and the dominant transport process can change with depth and stellar mass.

Radiative transport dominates when photons can carry the required flux without producing an excessively steep temperature gradient. When radiative transport becomes inefficient, buoyancy can make hotter material rise and cooler material sink, producing convection. Opacity, ionization state, mass, and composition determine which regime appears.

Helioseismology maps sound-speed structure in the Sun, neutrinos test core reactions, and asteroseismology measures oscillations in other stars. Surface abundances, luminosities, radii, and evolutionary tracks provide additional constraints on interior mixing and transport.

A star can contain a convective core, radiative envelope, radiative core, convective envelope, or nearly full convection depending on mass and composition. Opacity and the temperature gradient determine where photons can carry the required energy flux efficiently.