Astronomy Bio...Vesto Slipher

Jay Bitterman

Vesto M. Slipher was born on November 11, 1875 in Mulberry, Indiana. In 1902 after graduating Indiana University, at the request of Percival Lowell, he joined the Lowell Observatory in Arizona.

In 1903 he earned his MA and in 1909 his PhD at the University of Indiana plus a number of honorary degrees from many other universities. In 1916 he became the acting director of the Lowell Observatory and in 1926 its director until he retired in 1952. He launched the research that aided in Clyde Tombaugh's discovery of the planet Pluto in 1930. Slipher was an active member of the International Astronomical Union and the American Association for the Advancement of Science, including a number of other astronomical and scientific societies.

Slipher's studies included Venus, Mars and Jupiter. Due to the lack of detail on the surface of Venus his calculation of the rotation period was made difficult. His technique was to measure changes in the inclination of spectral lines while keeping a spectrograph perpendicular to the terminator. His 26 photographs closely agree with what is presently accepted on the basis of the present day computations. Slipher also published the measurements of the period of rotation for Mars, Jupiter, Saturn and Uranus. In 1933 he received the Gold Medal award from the Royal Astronomical Society for his work on planetary spectroscopy.

Slipher was credited with many planetary discoveries. Slipher and his colleagues' investigation of Jupiter were the first to indicate the existence of the elements iron and copper in its spectrum. He found that the spectrum of the diffuse nebula in the Pleiades was similar to its surrounding stars and concluded that the nebula's brightness was due to the reflected light from the stars. Another of Slipher's discoveries became instrumental to work done by Edwin Hubble, Ejnar Hertzsprung and others on emission and absorption nebulae. It depended on Slipher's recognizing the existence of particles of matter in interstellar space. He discovered a non- oscillating calcium line in the spectra of various celestial objects, which indicated that there was gas between the stars and the Earth. His most significant contribution to astronomy centered on spiral nebulae. His research opened the way for a better understanding of the motion of galaxies and cosmological theories to explain the expansion of the Universe. Although Hubble is given the credit for formulating the relationship between velocity and distance in interstellar space, it was Slipher's research into spiral nebulae that aided him.

In 1912 Slipher obtained a set of spectrographs that indicated that the Andromeda spiral nebula was nearing the Sun at a velocity of 300 km/sec. He looked for Doppler shifts for 14 other spirals while continually observing Andromeda. His 1925 catalogue included the radial velocities of almost all of the 44 known spirals. He concluded that spirals were external to our Galaxy since their radial velocities could not be contained within the Milky Way system. His work had an Influence not only on Heber Curtis and Edwin Hubble, each of which put forward an account of the nature of this phenomenon, but also other astronomers who had an interest in discovering the relationship between velocity and distance in interstellar space. Slipher's contribution to this field of study was phenomenal and extremely fundamental to astrophysics.

He died in Flagstaff Arizona on November 8, 1969.