Gravitational binding energy

The gravitational energy is in astrophysics, the term for the potential energy that is released during the contraction of celestial bodies. It is adjacent to the fusion, the source of high-energy radiation from stars and galaxies. For light or very extended celestial bodies, it plays only a marginal role.

Appraisal

According to Newton's law of gravitation, the gravitational energy is of the order of:

With:

If a very widely extended gas cloud contracted to form a star with the dimensions of the sun, is an energy of about 1041 J is available. Partly it heats the body, partly it is radiated as thermal energy and neutrinos.

For comparison:

• An oxyhydrogen mixture of the mass of the sun produces an energy of about 1033 J.
• The helium burning of the sun delivers an energy of 1045 J.
• The rotational energy of a rotating fast neutron star is in the order of 1040 J.

Homogeneous solid sphere

For the important case of a homogeneous solid sphere, the gravitational energy is calculated to

(for a detailed account see Article bond energy )

Observations

Transport processes that are required for the maintenance of a nuclear fusion, in stars limit the maximum radiant power. Many astronomical observations can not be explained, therefore, on this reaction process.

A star collapse of a sun -like structure to a neutron star decreases the radius of 16 km. In accordance with the coarse estimation of (1) where an energy on the order of 1046 J is emitted in a short time.

Through the release of gravitational energy to the illumination of supernovae or gamma-ray bursts can be explained, as are the high radiation power of active galactic nuclei.

The accretion is based on the same effect. For example, relate X-ray binaries, the energy from the contraction of a cloud of material around a neutron star.