Arthur Stanley Eddington (1882-1944), British astrophysicist, speaking at the Kepler memorial in Heidelburg, Germany, in 1928. Johannes Kepler's statue (upper right) and the word insAstronomiains (upper centre) are seen behind him. Eddington theorised an upper limit on the mass of a star and also discovered the mass-luminosity relationship. He was Chief Assistant at the Royal Greenwich Observatory (1906-1913), Plumian Professor at the University of Cambridge (1913-1944), and President of the Royal Astronomical Society (1921-1923). He was awarded the Gold Medal of the Royal Astronomical Society (1924), the Bruce Gold Medal of the Astronomical Society of the Pacific (1924), and the Royal Medal of the Royal Society (1928).