Kelvin–Helmholtz mechanism

The Kelvin - Helmholtz contraction ( also Kelvin contraction) describes the contribution of gravitational binding energy to the total luminosity of stars and planets.

Was first proposed, the mechanism of the physicists Lord Kelvin and Hermann von Helmholtz to solve the problem of where the sun gets radiated from her energy. 150 years ago, Kelvin was the age of the earth through the heat flow in the upper mantle on many millions of years estimated, so that a chemical energy source did not come into question. Based on current knowledge of the mechanism actually plays a role in the initial and late stages of stellar evolution, but the age of the sun is 4.7 billion years, two orders of magnitude over Kelvin's estimate, while the surface heat flow of the Earth's mantle, radioactive decay in the mantle and, no idea of Kelvin that contribute to shrinkage of the core by crystallization. In the theoretical models of star formation is the idea of ​​Kelvin -Helmholtz contraction that still a young protostar his budding radiation losses, covers of its potential energy. Here, the star is set according to the Kelvin - Helmholtz time a defined limit, which depends in large part on its luminosity.

Both Jupiter and Saturn, both planets radiate significantly more heat than they receive from the sun, it is discussed whether nuclear fusion or gravitational energy are responsible.