In the early 1920s, three candidates for white dwarfs were known. These stars were suggested to appear at the end of the star life cycle when the stars collapse under their own weight. The remaining material forms a star in a very dense state. One of the three white dwarfs, Sirius B, a companion to Sirius, was discovered by Walter Sydney Adams after a suggestion by Arthur Eddington to use the relativistic Doppler effect as predicted by special relativity. In 1926, Eddington pointed out a problem with the models at the time which considered such dense matter as the lowest energy state. Eddington suggested that it could not be the case as stars radiate and cool down. Ralph H. Fowler solved this issue by considering that the white dwarf is held for collapsing further due to electron degeneracy pressure.