What is a Kramers Opacity?

Question

I'm doing a summer research project (17 year old), and in order for some of my calculations to work, the stars need to satisfy Kramers opacity. What is this?

Answer 1

Kramer's Opacity refers to the fact that gases in a star are so dense that they are really opaque, or "cloudy", as opposed to being transparent ("clear", like Earth's atmosphere). The greater the opacity, the longer it actually takes light generated within the star to get to the surface. Because of this effect, it's estimated that radiation ("light") produced deep within the Sun's interior can take anywhere from 10,000 to 170,000 years to reach the surface of the Sun, where it then takes an additional 8 minutes to reach Earth.

In a star, Kramer's Opacity at a given depth equals the density of the gases at that dept divided by the temperature of those gases raised to the 3.5 power.