Willem Jacob Luyten (1899–1994)

Willem Jacob Luyten was born in Samarang, Java on 7 March 1899. At the age of 11, his uncle awakened him at 4:30 am and told him "Come on outside; there is something marvelous to see." It was Halley's Comet, and while the head was below the horizon, the end of the tail was past the zenith. That was a sight he never forgot and it was an experience that convinced him to become an astronomer.

Luyten returned to Holland with his family in 1912. He began his first observations of variable stars with field glasses and a small refracting telescope. Those observations led to his becoming a charter member of the American Association of Variable Star Observers at the age of 15. He entered the University of Amsterdam in 1916 and completed his B.A. examinations in mathematics and astronomy in June 1918. Luyten then went to the University of Leiden to work with Ejnar Hertzsprung, the Danish astronomer who had worked with Karl Schwarzschild at Potsdam and just had been appointed Professor in Leiden. During his years at Leiden, Luyten spent several summers at the Royal Observatory, Greenwich and wrote his first scientific paper. He also became a Fellow of the Royal Astronomical Society.

Upon completing his Ph.D. at Leiden in 1921 with a thesis on observations of variable stars, Luyten was offered a Morrison Fellowship at the Lick Observatory, in the mountains above San Jose, California. He arrived at Lick in September 1921 to begin a new research career in stellar motions and white dwarfs. In 1923 he was invited by Harlow Shapley to join the staff of the Harvard College Observatory. At Harvard, Luyten helped to improve a recently developed horizontal blink machine which placed the photographic plates in parallel, rather than in a single plane. His refined design eliminated various optical problems with the original design. With it he was able to compare photographic images taken at different times to identify and estimate stellar variability and stellar motions. This manual blink is now in the national collections of the Smithsonian Institution.

It was during his Harvard tenure that Luyten made a personal commitment to complete a proper motion study of the entire sky. But at Harvard he also embarked on many other activities. First, he became interested in astronomical journalism. The total eclipse of the sun on 25 January 1925 gave him an opportunity — he convinced the editor of the New York Times, Carr van Anda, to send up a plane to photograph the eclipse and the shadow of the moon as it moved across Manhattan. Luyten also wrote about the 1927 Lapland eclipse and his subsequent journey through Russia for the Boston Globe. He continued to write for the Times, the Globe and later for the Minneapolis Star and Tribune. He was elected to the American Academy of Arts and Sciences and appointed as an Assistant Professor of Astronomy at Harvard. In 1928 Luyten went to Bloemfontein, South Africa on a Guggenheim Foundation Fellowship to use the new telescope at Harvard's Radcliffe Observatory. Unfortunately the telescope was not yet operational, so he returned on an epic journey from the Cape to Cairo via car.

In the spring of 1931, Luyten was appointed an Assistant Professor of Astronomy at the University of Minnesota in Minneapolis, where he stayed for the rest of his life. During much of this time, he was a one-man department, teaching both undergraduates and graduate students. He continued his research actively, extending his interests from stellar motions and white dwarfs to include faint blue stars and low mass faint red dwarfs. From this expanded sample he made a determination of the stellar luminosity function for stars in the galaxy — an indicator of the frequency distribution of stars as a function of luminosity and hence mass. In later years some of his faint blue objects turned out to be quasars, which caused him to adjust his statistics.

He loved to make direct observations and always was testing his ideas against evidence in nature. This was difficult in Minneapolis, since there was no suitable telescope for research. Accordingly, he developed associations with many observatories, including the Mount Wilson and Hale Observatories, as well as those in Argentina, Mexico, and with those outside Tucson, Arizona. His research lead to the discovery of more than 80% of the known white dwarfs, which led Walter Baade to refer to Luyten as a Stellar Mortician.

No doubt Luyten's great legacy is the fact that over the course of his career he was able to determine the motions of 544,000 stars, which started with the Bruce Proper Motion Survey and ended with his monumental Luyten-Palomar proper motion survey. In the 1960s, faced with the daunting task of completing the survey of the sky that he had begun in 1925, Luyten worked closely with engineers at the Control Data Corporation to develop an automated measuring machine which could use lasers and computer techniques to compare photographic plates, discriminate flaws in the plates from stars and determine stellar motions. His contact with the engineers who later worked with him at CDC began in the early 1950s when they approached him for information on celestial navigation techniques useful in high-altitude balloon flight. Through this interaction the engineers learned of Luyten's interests and technical needs, and an effective liaison was forged. The eventual automatic blink project was supported by NASA in the 1960s and the machine was completed in 1970. In the years following its completion, Luyten was able to finish much of his original commitment.

He was a prolific scientist, having published 490 scientific articles during his 71 years of active research, as well as an additional 200 notes, reviews and newspaper articles. Luyten received many honors for his research in astronomy, including the Watson Medal of the National Academy of Sciences (1964), the Bruce Medal of the Astronomical Society of the Pacific (1966) and election to the National Academy of Sciences (1970). He was elected to the Century Association in New York in 1950 and was awarded the honorary D.Sc. from the University of st. Andrews in Scotland and from Case-Western Reserve. Luyten was also elected a Commandeur in the Confrerie des Chevaliers du Tastevin in France.

Willem J. Luyten died quietly on 21 November 1994 at home. He is survived by his wife, Willemina H. Luyten, three children, Mona L. Coetzee, Ann L. Dieperink and James R. Luyten, several grandchildren and one great-grandchild. He authored an autobiography, My First 72 Years of Astronomical Research (1987), which was published privately, and his papers have been donated to the University of Minnesota Archives. Among his obituary notices are: "Willem Jacob Luyten," by Arthur Upgren, PASP 107 (1995), 603-605.