Vesto Melvin Slipher | |
|---|---|
| Born | (1875-11-11)November 11, 1875 Mulberry, Indiana, United States |
| Died | November 8, 1969(1969-11-08) (aged 93) Flagstaff, Arizona, United States |
| Alma mater | Indiana University Bloomington (BS,MS,PhD) |
| Known for |
|
| Spouse | |
| Children | 2 |
| Relatives | Earl C. Slipher (brother) |
| Scientific career | |
| Fields | Astronomy |
| Institutions | Lowell Observatory |
Vesto Melvin Slipher (/ˈslaɪfər/; November 11, 1875 – November 8, 1969) was an Americanastronomer who performed the first measurements of radial velocities for galaxies. He was the first to discover that distant galaxies areredshifted, thus providing the first empirical basis for the expansion of the universe.[1][2][3][4] He was also the first torelate these redshifts to velocity.[5]
Vesto Melvin Slipher was born inMulberry, Indiana, to Daniel Clark and Hannah App Slipher. He spent his early years working on his family farm in Mulberry.[6] Vesto had a younger brother,Earl C. Slipher, who was also an astronomer atLowell Observatory.[6]Slipher went to high school inFrankfort, Indiana. He then attendedIndiana University Bloomington and earned his Bachelor's Degree in Mechanics and Astronomy in June 1901.[7] Two years later, Slipher earned his Master's Degree in the same program.[7] At the age of 33, Vesto graduated with his Ph.D. in Mechanics and Astronomy from Indiana University.[7]
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.[8] Cogshall convincedPercival Lowell, director of the Lowell Observatory inFlagstaff, Arizona, to take Vesto in as a temporary assistant.[8] Slipher worked as an assistant from 1901 to 1915 when Lowell finally named him the assistant director of the observatory.[9] One year later Percival Lowell died and Vesto became the acting director for the next ten years.[9] In 1926, 25 years after arriving in Flagstaff, Slipher was named director of the Lowell Observatory.[9] He remained in charge for 28 more years when he retired from professional life.[9] Slipher spent his years there studying many things, but most notably,spectroscopy and redshifts ofspiral nebulae.
The first major task Slipher was given was to measure theSolar System's planets' rotation interval.[10] He was one of the first astronomers to show thatUranus has a much faster rotation thanEarth, similar to the othergiant planets in the Solar System.[10] What Vesto is most known for though is his work with spiral nebulae, or, spiral galaxies, like theMilky Way andAndromeda.[10] His initial goal was to measure how fast the nebulae were moving.[10] His discoveries were confirmed ten years later whenEdwin Hubble used theMount Wilson Observatory reflector to view the galaxies much more clearly.[10]
Slipher introduced as early as 1909 that theinfrared spectrum could be recorded usingphotographic emulsions, and used those to record the absorption lines of sunlight and major planets.[11] He found that the planets showed different absorption lines that were not present in sunlight, and identified those bands withammonia andmethane.[11] In the early twentieth century, Vesto Slipher elongated the spectrum to include the red and infrared wavelengths and showed that the major planets display strong absorption lines at many different wavelengths.[12] Slipher usedspectroscopy to investigate the rotation periods ofplanets and the composition of planetary atmospheres. In 1912, he was the first to observe the shift of spectral lines ofgalaxies, making him the discoverer of galacticredshifts.[13] Using the Doppler effect and noting subtle changes, he measured the speeds in which spiral nebulae traveled during his research from 1912 and onward.[14]These subtle changes in the speeds of the nebulae led Slipher to conclude that the nebulae were not within the Milky Way galaxy.[15] In 1914, Slipher also made the first discovery of the rotation of spiral galaxies.[16]He discovered thesodium layer in 1929.[17] He was responsible for hiringClyde Tombaugh and supervised the work that led to the discovery ofPluto in 1930.[1]
By 1917, Slipher had measured the radial velocities of 25 "spiral nebulae," and found that all but three of those galaxies were moving away from us, at substantial speeds. Slipher himself speculated that this might be due to the motion of our own galaxy – as in his sample, those galaxies moving towards us and those moving away from us were roughly in opposite directions.[18] In hindsight, this was the first data supporting models of anexpanding 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 termedthe Hubble–Lemaître law (formerly named Hubble's law; the IAU Decision of October 2018 recommends the use of a new name[19]), was formulated by Hubble and Humason in 1929 and became the basis for the modern model of theexpanding universe.
Slipher married Emma R. Munger in 1904 in Frankfort, Indiana. Vesto and Emma had two children – David Clark and Marcia Frances.[20]
In 1901 Slipher moved toFlagstaff, Arizona, and began work at Lowell Observatory.[20] He continued at Lowell as an assistant and as the director until his retirement in 1954. Slipher died in Flagstaff in 1969 at age 93.[20] He is buried atCitizens Cemetery in Flagstaff.[21][22]
{{cite book}}: CS1 maint: others (link){{cite book}}: CS1 maint: others (link)| International | |
|---|---|
| National | |
| Academics | |
| People | |
| Other | |
