Astronomy Bio...Milton Humason

Jay Bitterman

Milton Lasell Humason was an American astronomer famous for his investigation, at Mount Wilson Observatory, into distant galaxies. Born at Dodge Center, Minnesota on August 19, 1891. He died suddenly at his home near Mendocino, California, on June 18, 1972.

When he was 14 his parents sent him to a summer camp on Mount Wilson and because he enjoyed it, he obtained permission from his parents to take a year off school and return there. His "year" was extended well beyond twelve months and he became one of astronomy's most notable educational dropouts. Sometime between 1908 and 1910, after he dropped out from higher education, he became a mule driver for the packtrains that traveled the trail between the Sierra Madre and Mount Wilson during construction work on the Observatory. He brought up much of the timber and other building materials for the telescope's supporting structure, the local cottages and the scientists' quarters.

He became engaged and married the daughter of the Observatory's engineer her in 1911. In the same year he gave up his job as a packtrain driver and went to be foreman on a relative's range in La Verne. But he still loved Mount Wilson and in 1917, when a janitor was leaving, his father-in-law suggested that this would be an opportunity to better himself. So Humason initially joined the staff of Mount Wilson Observatory as a janitor. His position was soon raised to night assistant. In 1919 George Hale, the Director of the Observatory at the time, recognized Humason's unusual ability as an observer and was appointed to the scientific staff. There was considerable opposition to this appointment, partly because Humason had no formal education after the age of 14 and partly because he was the Observatory engineer's son-in law

From 1919 to 1954 Humason was Assistant Astronomer and then Astronomer at both the Mount Wilson and Palomar Observatories. In 1947 he was appointed Secretary of the Observatories, a position which involved him in handling public relations and administrative duties. In 1950 he was awarded the honorary degree of Doctor of Philosophy by the University of Lund in Sweden.

He was a quiet, friendly man who was often consulted on administrative and personal problems. At Mount Wilson Observatory he was extensively involved in a study of the properties of galaxies that was started by Edwin Hubble. In 1928 the research program began and consisted of making a series of systematic spectroscopic observations to test and extend the relationship that Hubble had established between the red shifts and the apparent magnitudes of galaxies. But because of the low surface brightness of galaxies there were many technical difficulties. With the use of the Rayton lens and the solid block Schmitt camera it became possible to obtain a spectrum of a galaxy too faint to be picked up visually with the telescope in use. The method was to photograph the field containing the galaxy and accurately measure the position of its image with respect to two or more bright stars. Guide microscopes were then set up at the telescope with exactly the same offsets from the slit of the spectrograph. It was a tedious task and often took several nights of exposure to produce a spectrum on a 12.7 mm (half-inch) plate.

Humason undertook this exacting program and personally developed a technique for determining the exposures and plate measurements. During the period from 1930 until his retirement in 1957, he measured the velocities of 620 galaxies. He used the 100-inch (2.5 m) telescope. When the 200 inch (5 m) Hale telescope was available the program was shifted. Humason's results were published jointly with those of N.U. Mayall and A. R. Sandage in "Redshifts and Magnitudes of Extragalactic Nebulae", which appeared in the Astronomical Journal of 1956. This data still represents the majority of known values of radial velocities for normal galaxies, including most of the large values.

Humason applied the techniques he had developed for recording spectra of faint objects to the study of supernovae, old novae that were well past peak brightness, and faint blue stars (including white dwarfs). During his studies on galaxies he discovery the Comet 1961e which is notable for its large perihelion distance and its four-year period of visibility with remarkable changes in it's form.

Humason will be remembered for his ability to handle instruments with meticulous care and great skill. He also provided criteria for studying various models of the Universe. He is internationally famous for his work on galaxies and, in spite of his lack of formal training, won a leading role in American astronomy.

Published in the August 1999 issue of the NightTimes