Mass–luminosity relation

Article By:

Popper, Daniel M. Department of Astronomy, University of California, Los Angeles, California.

Last reviewed:June 2020

DOI:https://doi.org/10.1036/1097-8542.408510

The relation, observed or predicted by theory, between the quantity of matter a star contains (its mass) and the amount of energy generated in its interior (its luminosity). Because of the great sensitivity of the rate of energy production in a stellar interior to the mass of the star, the mass–luminosity relation provides an important test of theories of stellar interiors. This predicted relation is a corollary of the more general principle that if a star is in equilibrium—it is neither expanding nor contracting—all its other properties depend only on its mass and the distribution of chemical elements within it. For a family of stars with different masses but with the same mixture of chemical elements uniformly distributed throughout the stellar volumes, there should be a unique mass–luminosity relation. The observed relation, obtained from binary stars for which masses and luminosities can be observationally evaluated, is shown in the illustration. The majority of stars placed on such a plot are found along this relation, called the main sequence, and it implies that all stars begin their lives with roughly the same chemical composition. It conforms reasonably well to theory. It was this agreement that showed the pioneering studies of stellar structure by A. S. Eddington in the 1920s to be on a sound basis. See also: Binary star; Star

The content above is only an excerpt.