## FANDOM

155 Pages

Kelvin Helmholtz time scale is an estimate of the time it takes a star to collapse after nuclear burning ceases. This time scale is obtained by taking the ratio of the gravitational binding energy and the luminosity

$t_{KH} = \frac{GM^2}{RL}$

where $G$ is the gravitation constant, $M$ is the mass of the star, $R$ is its radius and $L$ its luminosity. For example, the Kelvin Helmholtz time of our sun is about 30 million years.