Francis G. Pease

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The 100-inch reflector ("Hooker's mirror") at the Mount Wilson Observatory

Francis Gladheim Pease (born January 14, 1881 in Cambridge , Massachusetts , † February 7, 1938 in Pasadena , California ) was an American astronomer .

Pease was born in Cambridge, MA . His parents soon moved to Illinois , so he attended high school in Highland Park and then studied at the Armor Institute of Technology in Chicago .

From 1901 Pease worked at the Yerkes Observatory . There he studied optical design and manufacturing processes under GW Ritchey . He gained practical experience in building instruments, but also worked as an astronomical observer with the observatory's 24-inch reflector .

In 1904, Pease went to Pasadena with George Ellery Hale and Ritchey to build the newly established Mount Wilson Observatory . Together with Ritchey, he constructed most of the new equipment for the observatory. He was partly responsible for the construction of the Snow Telescope, the 60- foot and 150-foot tower telescopes, and the 60- inch reflector. He did most of the construction of the 100-inch reflector. In particular, he oversaw the design and testing of the larger telescope mirrors.

Pease also worked as an observer on Mount Wilson: he used the 60-inch monitor to observe and photograph nebulae and star clusters . He carried out spectroscopic measurements, which among other things led to the first observation of the rotation of extragalactic nebulae. With the 100-inch model, he took photographs of the moon, which contributed to the creation of a photographic map of the moon.

Michelson's 20-foot interferometer, mounted on the 100-inch reflector (1920)

Pease assisted Albert A. Michelson in 1920 with the first successful measurements of star diameters with the help of an interferometer . Michelson had found that even the 2.5 m opening of the 100-inch model was not sufficient as an interferometer base to determine the diameter of Betelgeuse . So they attached a 20 foot (6 meter) long interferometer arm to this telescope, which carried small mirrors at both ends, thus increasing the base width. They succeeded in determining the diameter of Betelgeuse to be 0.047 " ± 10% (consistent with the modern value 0.0566" ± 0.0010 "). Measurements followed on several other bright stars. Pease later conducted these studies with one 50-foot interferometer continued.

When Michelson repeated his earlier measurements of the speed of light in the years 1924–1928 , Pease supported him in building the measuring apparatus and in carrying out the observations. Another repetition of these measurements, begun in 1930 and completed in 1934, using a one- mile- long evacuated pipe, was largely carried out by Pease himself because of Michelson's illness.

In 1929, Pease repeated Michelson and Morley's ether drift experiment with a path length of 85 feet and also got a negative result.

Pease studied construction principles for particularly large telescopes. After work on the 200-inch Hale Telescope for the Palomar Observatory began in 1930 , he devoted half of his time to these design designs.

In 1928, Pease discovered the first planetary nebula located in a globular cluster, Pease 1 , which was later named after him. A lunar crater with a diameter of 38 km was named after him.

literature

  • CH Townes: Michelson & Pease's Interferometric Stellar Diameters. In: Astrophysical Journal. Centennial Issue, Vol. 525C, 1999, p. 148 ( online )

Web links

Individual evidence

  1. ^ Gazetteer of Planetary Nomenclature: Pease
personal data
SURNAME Pease, Francis G.
ALTERNATIVE NAMES Pease, Francis Gladheim
BRIEF DESCRIPTION American astronomer
DATE OF BIRTH January 14, 1881
PLACE OF BIRTH Cambridge , Massachusetts
DATE OF DEATH February 7, 1938
Place of death Pasadena , California