In Astrophysical, the mechanism of Kelvin-Helmholtz is a phenomenon which takes place when the surface of a star or a Planet cools. This cooling involves a fall of Pression and the celestial body compensates for it while contracting. This compression then involves a warming of the center of the body. This mechanism is observable in an obvious way for Jupiter and Saturn.

This mechanism was initially proposed by Lord Kelvin and Helmholtz towards the end of the 19th century in order to explain the source of energy Sun. It on the other hand was given that the quantity of energy generated by this process is too weak to feed the Sun.