Kelvin-Helmholtz contraction
The Kelvin-Helmholtz contraction (also called Kelvin contraction ; after the physicists Lord Kelvin and Hermann von Helmholtz , who proposed this contraction) describes the contribution of gravitational binding energy to the total luminosity of celestial bodies such as stars and objects of planetary mass .
In the theoretical models of star formation , the idea of the Kelvin-Helmholtz contraction is that a protostar covers its future radiation losses from its potential energy . With the Kelvin-Helmholtz time, a firmly defined limit is set for the star , which largely depends on its luminosity.
The mechanism of the Kelvin-Helmholtz mechanism was proposed as a solution to the problem of where the sun radiated from her energy receives. About 150 years ago, Kelvin estimated the age of the earth from the heat flow in the upper mantle to be many millions of years, so that a chemical energy source was out of the question. According to current knowledge, the mechanism actually plays a role in the early and late phases of stellar evolution. However, at 4.7 billion years, the age of the sun is two orders of magnitude higher than Kelvin's estimate, while mantle convection , radioactive decay in the mantle and, disregarding Kelvin, the shrinking of the earth's core due to crystallization contribute to the earth's superficial heat flow .
For both Jupiter and Saturn , which both emit significantly more heat than they receive from the sun, it is being discussed whether gravitational energy is responsible for this .
See also
Individual evidence
- ↑ Miguel A. Morales et al .: Phase separation in hydrogen-helium mixtures at Mbar pressures. PNAS , February 3, 2009; accessed January 20, 2019 . doi : 10.1073 / pnas.0812581106