Vesto Melvin Slipher

Vesto Melvin Slipher , 1875-1969, American astronomer, b. Mulberry, Ind. From 1901 he was at Lowell Observatory, Flagstaff, Ariz., where he served as director (1917-54). Much of his attention was devoted to the investigation of astronomical spectroscopy, in particular to the rotations and atmospheres of planets and nebulae. His major contribution was determining that the spectra of the vast majority of external galaxies had red shifts . This crucial discovery laid the foundation for Hubble's law and the theory of the expansion of the universe. His brother, Earl C. Slipher, 1883-1964, was a noted planetary astronomer who also worked at the Lowell Observatory. His many years of observations of the planet Mars were published in 1962 as The Photographic Story of Mars.

Slipher, VestoMelvin (1875–1969)Americanspectroscopist, brother of E. C.Slipher. At Lowell Observatory he used spectroscopy to measure planetary rotation periods and atmospheric compositions. In 1912 he obtained the first radial-velocity measurements from the spectrum of a so-called ‘spiral nebula’ (the Andromeda Galaxy). By 1925 he had 45 radial velocities of other such nebulae, nearly all of which were receding too fast to belong to the Milky Way. This was the observational foundation for theories of an expanding Universe. In 1912 he discovered the existence of reflection nebulae from a study of the nebulosity around the Pleiades, proving that there is dust as well as gas in space. He supervised the photographic search that led to C. W.Tombaugh's discovery of Pluto in 1930.