Statistical physics a probabilistic examination of the underlying microscopic systems. Historically, one of the first topics in physics where statistical methods were applied was the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force. Statistical mechanics provides a framework for relating the microscopic properties of individual atoms and molecules to the macroscopic or bulk properties of materials that can be observed in everyday life, therefore explaining thermodynamics as a natural result of statistics, classical mechanics, and quantum mechanics at the microscopic level. Because of this history, the statistical physics is often considered synonymous
Molecules in stars don't allow atoms to form molecules. Stars have very high temperatures, primarily in their interior, and therefore there are few molecules formed in stars. For this reason, a chemist (who studies atoms and molecules) would not have much to study in a star, so stars are better explained by physicists. However, low abundance of molecules in stars is not equated with no molecules at all. Although the Sun is a star, its photosphere has a low enough temperature of 6,000 kelvins, and therefore molecules can form. Water has been found on the Sun, and there is evidence of H in