1938

Ernst Öpik presented the theory of the inner structure of the stars and showed that the direction of the evolution of the star was from the stars of the main sequence to the red giant stars.

The recognized leading theoretician in this field was Arthur Eddington (1882–1944) under whose influence the general viewpoint that stars develop from the red giant stars into dwarf stars was prevailing. Öpik showed that the development of stars had the opposite direction – from the stars of the main sequence to the red giant stars.

The life-cycle of a star (www.enchantedlearning.com/subjects/astronomy/stars/lifecycle/)