- 560

- 2

"When reaching point 2 in the HR-diagram, the radius of the star has

been increasing so much that the surface temperature is close to 2500 K

which is a lower possible limit. When reaching this limit, the dominant

mechanism of energy transport in the star changes from being radiation

to convection. Convection is much more efficient, the energy is released

at a much larger rate and the luminosity increases rapidly."

"When reaching point 2 in the HR-diagram, the radius of the star has

been increasing so much that the surface temperature is close to 2500 K

which is a lower possible limit. When reaching this limit, the dominant

mechanism of energy transport in the star changes from being radiation

to convection. Convection is much more efficient, the energy is released

at a much larger rate and the luminosity increases rapidly."

Two questions: why does convection start to dominate over radiation at 2500K, and why is convection -- in general -- a more efficient way of transporting energy than radiation?