Describe Why Energy Must Flow in Stars and Two Ways It Can Flow in Normal Stars.

Energy must flow in stars in order to balance the force of gravity and maintain stability. If energy did not push (flow), the star would collapse in on itself due to gravitational forces. The energy produced by stars creates massive amounts of heat. Heat naturally flows from a hotter area to a cooler area; therefore heat flows from the center of the star out towards the surface, because the core of a star is much hotter than the surface. There are three ways heat can flow from a hot area to a cooler area: conduction, radiation or convection.

Two ways heat can flow in normal stars are by radiation and convection, the processes in our sun.

Convection can be defined as fluid circulation that is heat driven. We can see convection at work if we put some cold milk into a hot cup of tea without stirring it; the cold milk will sink, warm up, expand, rise to the top, cool again, and sink again etc. leaving spots of milk on the top of the tea where the heated milk 'broke through' the surface and the heat escaped. Similarly, our sun has regions of convection at its surface, where hot gas comes up in the middle of the region, flows to the edge and sinks back down again. These regions are about the size of Texas and are called granules.

The radiative area of the sun is between the core and the convective area. In this region, gamma rays produced by the hot core bounce off of electrons and are scattered in random directions. Eventually, the gamma rays make their way outward to cooler areas; are absorbed and re-emitted first as X-rays, then as photons of increasing wavelength, over and over until they reach the convective area.

Conduction is insignificant in most stars because it requires particles to be in close contact with each other to work effectively. In normal stars, particles are not in close contact. White dwarfs (which are not really stars) utilize conduction.