In the core of a star the intense heat destroys the internal
structure of an atom and consequently all atoms are
broken down into their constituent
parts. An atom is constructed of protons, electrons and neutrons. Neutrons
have no electric charge and therefore do not interact much with the
surrounding medium. As a result neutrons leave the core fairly quickly. The
protons, which have positive electric charge, and the
electrons, which have negative electric charge, remain in the core and
drive the reactions which fuel the Sun. The
charge neutral material of protons and electrons that makes up the core is
called plasma.
The high temperature provides the protons and
electrons with a large amount of thermal energy and as a result they move
around quite quickly. This motion, combined with the high density of the
plasma, causes the particles to continuously slam into one another creating
nuclear reactions. It is the fusion, or slamming together, of particular
combinations of particles that provides the energy source of the Sun.