Brown dwarfs and the minimum mass of stars

Abstract

Stars form from large clouds of gas and dust that contract under their own gravity. The birth of a star occurs when a fusion reaction of hydrogen into helium is ignited in its core. The key variable that determines the formation of a star is mass. If the mass of the contracting cloud is below a certain minimum value, instead of a star, a substelar object—known as a brown dwarf—will form. How much mass is required for a star to form? This article aims to answer this question by means of a simple heuristic argument. The found value is ∼0.016 solar masses, which is of the same order of magnitude as the accepted value, ∼0.08 solar masses. This article may be useful as pedagogical material in an introductory undergraduate astronomy course.