Solar energy is produced by interactions of particles—that is, protons, neutrons, electrons, positrons, and neutrinos. Specifically, the source of the Sun’s energy is the fusion of hydrogen to form helium.

Since Earth and the solar system are roughly 4.5 billion years old, this means that the Sun has been producing vast amounts for energy for a very, very long time. The series of reactions required to convert hydrogen to helium is called the proton-proton chain.

neutrino — fundamental particle that has no charge and a mass that is tiny relative to an electron; it rarely interacts with ordinary matter and comes in three different types. solar system — roughly 4.5 billion years old, this means that the Sun has been producing vast amounts for energy for a very, very long time. helium atom — about 0.71% less massive than the four hydrogen atoms that combine to form it, and that lost mass is converted to energy (with the amount of energy given by the formula E. proton-proton chain — series of thermonuclear reactions by which nuclei of hydrogen are built up into nuclei of helium.