Vesto Slipher

Vesto Melvin Slipher was born in Mulberry, Indiana, to Daniel Clark and Hannah App Slipher. He spent his early years working on his family farm in Mulberry. Vesto had a younger brother, Earl C. Slipher, who was also an astronomer at Lowell Observatory. Two years later, Slipher earned his Master's Degree in the same program. At the age of 33, Vesto graduated with his Ph.D. in Mechanics and Astronomy from Indiana University. ==Career==

While at school at Indiana University, Slipher formed a personal bond with one of his professors, William Cogshall. Cogshall was one of the main reasons Slipher became interested in astronomy in the first place. Slipher worked as an assistant from 1901 to 1915 when Lowell finally named him the assistant director of the observatory. Slipher spent his years there studying many things, but most notably, spectroscopy and redshifts of spiral nebulae. The first major task Slipher was given was to measure the Solar System's planets' rotation interval. He was one of the first astronomers to show that Uranus has a much faster rotation than Earth, similar to the other giant planets in the Solar System. What Vesto is most known for though is his work with spiral nebulae, or, spiral galaxies, like the Milky Way and Andromeda. His initial goal was to measure how fast the nebulae were moving. His discoveries were confirmed ten years later when Edwin Hubble used the Mount Wilson Observatory reflector to view the galaxies much more clearly. ==Discoveries==

in California Slipher introduced as early as 1909 that the infrared spectrum could be recorded using photographic emulsions, and used those to record the absorption lines of sunlight and major planets. He found that the planets showed different absorption lines that were not present in sunlight, and identified those bands with ammonia and methane. Slipher used spectroscopy to investigate the rotation periods of planets and the composition of planetary atmospheres. In 1912, he was the first to observe the shift of spectral lines of galaxies, making him the discoverer of galactic redshifts. Using the Doppler effect and noting subtle changes, he measured the speeds in which spiral nebulae traveled during his research from 1912 and onward. These subtle changes in the speeds of the nebulae led Slipher to conclude that the nebulae were not within the Milky Way galaxy. In 1914, Slipher also made the first discovery of the rotation of spiral galaxies. He discovered the sodium layer in 1929. He was responsible for hiring Clyde Tombaugh and supervised the work that led to the discovery of Pluto in 1930. In hindsight, this was the first data supporting models of an expanding universe. Later, Slipher's and additional spectroscopic measurements of radial velocities were combined by Edwin Hubble with Hubble's own determinations of galaxy distances, leading Hubble to discover the (at that time, rough) proportionality between galaxies' distances and redshifts, which is today termed the Hubble–Lemaître law (formerly named Hubble's law; the IAU Decision of October 2018 recommends the use of a new name), was formulated by Hubble and Humason in 1929 and became the basis for the modern model of the expanding universe. ==Personal life==

Slipher married Emma R. Munger in 1904 in Frankfort, Indiana. Vesto and Emma had two children – David Clark and Marcia Frances. In 1901 Slipher moved to Flagstaff, Arizona, and began work at Lowell Observatory. ==Awards==

• Member of the American Academy of Arts and Sciences (elected 1909) • Lalande Prize (1919) • Member of the American Philosophical Society (1921) • Henry Draper Medal of the National Academy of Sciences (1932) • Gold Medal of the Royal Astronomical Society (1932) • Bruce Medal (1935) • The crater Slipher on the Moon is named after Earl and Vesto Slipher, as is the crater Slipher on Mars and the asteroid 1766 Slipher, discovered September 7, 1962, by the Indiana Asteroid Program. ==References==