** Based on F.W. Astons measurements of the masses of low-mass elements and Einsteins discovery that E=mc, Arthur Eddington proposes that large amounts of energy released by fusing small nuclei together provides the energy source that powers the stars.
** Henry Norris Russell notes that the relationship in the Hertzsprung–Russell diagram suggests a hot core rather than burning throughout the star. Eddington uses this to calculate that the core would have to be about 40 million Kelvin. This was a matter of some debate at the time, because the value is much higher than what observations suggest, which is about one-third to one-half that value.
** George Gamow introduces the mathematical basis for quantum tunnelling.
** Atkinson and Houtermans provide the first calculations of the rate of nuclear fusion in stars. Based on Gamows tunnelling, they show fusion can occur at lower energies than previously believed. When used with Eddingtons calculations of the required fusion rates in stars, their calculations demonstrate this would occur at the lower temperatures that Eddington had calculated.