Vesto Slipher

Infobox person


caption=
name=Vesto Melvin Slipher
birth_date=birth date|1875|11|11
birth_place=Mulberry, Indiana
death_date=dda|1969|11|08|1875|11|11
death_place=Flagstaff, Arizona
nationality=American
occupation=Astronomer
employer=Lowell Observatory
relatives=Earl C. Slipher (brother)
known_for=Expanding universe

Vesto Melvin Slipher (November 11, 1875 – November 8, 1969) was an American astronomer.Citation
last =
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publication-date = November 10 1969
date = November 9 1969
year = 1969
title = Nesto Slipher, 93, Astronomer, Dies
periodical = The New York Times
series =
place = Flagstaff, AZ
publisher =
volume =
issue =
page = 47
url =
issn = 1452424
doi =
oclc =
accessdate = 2008-04-17] His brother Earl C. Slipher was also an astronomer and a director at the Lowell Observatory. His children are son David C. Slipher and daughter K. J. Nicholson

Slipher was born in Mulberry, Indiana, and completed his doctorate at Indiana University in 1909. He spent his entire career at Lowell Observatory in Flagstaff, Arizona, where he was promoted to assistant director in 1915, acting director from 1916, and finally director from 1926 until his retirement in 1952. He used spectroscopy to investigate the rotation periods of planets, the composition of planetary atmospheres. In 1912, he was the first to observe the shift of spectral lines of galaxies, so he was the discoverer of galactic redshifts. [Slipher first reports on the making the first Doppler measurement on September 17, 1912 in [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1913LowOB...1b..56S&db_key=AST&data_type=HTML&format=&high=448f04e38822894 "The radial velocity of the Andromeda Nebula"] in the inaugural volume of the "Lowell Observatory Bulletin", pp.2.56-2.57. In his report Slipher writes: "The magnitude of this velocity, which is the greatest hitherto observed, raises the question whether the velocity-like displacement might not be due to some other cause, but I believe we have at present no other interpretation for it." Three years later, Slipher wrote a review in the journal "Popular Astronomy", Vol. 23, p. 21-24 [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1915PA.....23...21S&db_key=AST&data_type=HTML&format=&high=448f04e38822894 "Spectrographic Observations of Nebulae"] , in which he states, "The early discovery that the great Andromeda spiral had the quite exceptional velocity of - 300 km(/s) showed the means then available, capable of investigating not only the spectra of the spirals but their velocities as well." Slipher reported the velocities for 15 spiral nebula spread across the entire celestial sphere, all but three having observable "positive" (that is recessional) velocities.] He was responsible for hiring Clyde Tombaugh and supervised the work that led to the discovery of Pluto in 1930.

Edwin Hubble was generally incorrectly credited with discovering [This had actually been observed by Vesto Slipher in the 1910s, but the world was largely unaware. Ref: Slipher (1917): Proc. Amer. Phil. Soc., 56, 403.] the redshift of galaxies; these measurements and their significance were understood before 1917 by James Edward Keeler (Lick & Allegheny), Vesto Melvin Slipher (Lowell), and William Wallace Campbell (Lick) at other observatories.

Combining his own measurements of galaxy distances with Vesto Slipher's measurements of the redshifts associated with the galaxies, Hubble and Milton Humason discovered a rough proportionality of the objects' distances with their redshifts. Though there was considerable scatter (now known to be due to peculiar velocities), Hubble and Humason were able to plot a trend line from the 46 galaxies they studied and obtained a value for the Hubble-Humason constant of 500 km/s/Mpc, which is much higher than the currently accepted value due to errors in their distance calibrations. Such errors in determining distance continue to plague modern astronomers (See cosmic distance ladder for more details).

In 1929 Hubble and Humason formulated the empirical Redshift Distance Law of galaxies, nowadays termed simply Hubble's law, which, once the redshift is interpreted as a measure of recession speed, is consistent with the solutions of Einstein’s General Relativity Equations for a homogeneous, isotropic expanding space de Sitter universe or de Sitter space. Although concepts underlying an expanding universe were well understood earlier, this statement by Hubble and Humason lead to wider scale acceptance for this view. The law states that the greater the distance between any two galaxies, the greater their relative speed of separation.

This discovery later resulted in formulation of the Big Bang theory by George Gamow, a consequence of the observed velocities of distant galaxies that when taken together with the cosmological principle imply that space is expanding according to the Friedmann-Lemaître model of general relativity.

He died in Flagstaff, Arizona and is buried there in Citizens Cemetery.

Awards

*Lalande Prize (1919)
*Gold Medal of the Paris Academy of Sciences (1919)
*Henry Draper Medal of the National Academy of Sciences (1932)
*Gold Medal of the Royal Astronomical Society (1932)
*Bruce Medal (1935)
*Slipher crater on the Moon is named for Earl and Vesto Slipher, as is a crater on Mars and the asteroid 1766 Slipher, discovered September 7, 1962, by the Indiana Asteroid Program.

Notes

External links

* [http://www.lowell.edu/Research/library/paper/vm_slipher.html Library of Lowell Observatory: Biography of V. M. Slipher]
* [http://www.roe.ac.uk/~jap/slipher/ The Royal Observatory, Edinburgh: History, Papers & External Links on V. M. Slipher]