How does energy travel from the Sun’s interior to its surface?

Energy generated in the Sun’s core through nuclear fusion travels to the surface via two primary mechanisms: radiation and convection.

In the dense interior, energy is carried outward by gamma-ray photons. Because the solar interior is extremely dense, these photons undergo a random walk, constantly being scattered, absorbed, and reemitted by atoms. This process is highly inefficient, requiring approximately 170,000 years for energy to migrate from the core to the outer layers.

As energy reaches the outer 30 percent of the Sun, the temperature gradient becomes steep enough to trigger convection. In this convective zone, heat is transported by massive currents of hot plasma that rise toward the surface. Atoms are ionized at the base of this zone and release their energy upon recombining in cooler, upper regions. Near the surface, radiation transport becomes efficient again, though the convective motions remain visible in the photosphere.1