ABSTRACT
A star is by definition a celestial object, bound by self-gravity, in which thermal energy is produced from a nonthermal source (nuclear reactions) and is radiated outward from the object’s surface to its surroundings. We shall extend this definition somewhat so as to include objects such as white dwarfs and neutron stars which produced nuclear energy in their past, as well as objects that are in the process of becoming stars (protostars). According to this definition, planets, meteorites, comets, and other similar celestial objects are not stars.
