stellar structure
Stellar structure, physical properties of a star and the processes taking place within it. Except for that of the sun, astronomers must draw their conclusions regarding stellar structure on the basis of light and other radiation from stars that are light-years away; this light enables them to observe only the stars' surfaces. Knowledge of the processes taking place in a star and of conditions within its interior must be inferred from the laws of physics and chemistry. A star is a nearly spherical body of incandescent gas, mostly hydrogen and helium. Because it is observed to be stable, astronomers can conclude that the inward pressure of gravitation holding the star together is balanced by the outward pressure due to the energy generated by the star, and that the rate at which energy is radiated away from the star's surface is equal to the rate at which it is produced in the interior. The most important properties of a star are its size, mass, luminosity, chemical composition,