Vesto Melvin Slipher (; November 11, 1875 – November 8, 1969) was an American astronomer who performed the first measurements of radial velocities for galaxies. He was the first to discover that distant galaxies are redshifted, thus providing the first empirical basis for the expansion of the universe. He was also the first to relate these redshifts to velocity.

Early life and education

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. 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. 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.

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

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Sources

  • Library of Lowell Observatory: Biography of V. M. Slipher
  • The Royal Observatory, Edinburgh: History, Papers & External Links on V. M. Slipher
  • V. Slipher @ Astrophysics Data System