Slipher, Vesto Melvin (18751969), a United States astronomer. He made perhaps more basic contributions in various fields of astronomy than any of his contemporaries, Slipher is best known for his fundamental spectroscopic discoveries, especially of the rotations and atmospheres of planets. He also pioneered in the measurement of the rotations of galaxies and their movement through space, providing observational evidence for the expanding-universe theory. Slipher was born in Clinton County, Indiana, and graduated from Indiana University. He served as director of the Lowell Observatory at Flagstaff, Arizona, 191752.