Lectures on Physics has been derived from Benjamin Crowell's Light and Matter series of free introductory textbooks on physics. See the editorial for more information....

A reaction occurring in the sun

One can not even imagine the tremendous energy released by the nuclear fusion in the sun. Photo courtesy NASA.
The sun produces its energy through a series of nuclear fusion reactions. One of the reactions is

1H + 2H → 3He + γ

The excess energy is almost all carried off by the gamma ray (not by the kinetic energy of the helium-3 atom). The binding energies in units of pJ (picojoules) are:

1H 0 J

2H 0.35593 pJ

3He 1.23489 pJ

The total initial potential energy is 0 pJ+0.35593 pJ, and the final potential energy is 1.23489 pJ, so by conservation of energy, the gamma ray must carry off 0.87896 pJ of energy. The gamma ray is then absorbed by the sun and converted to heat.
See A Trip Into Space for more photos of the sun.

Last Update: 2010-11-11