Willem Jacob Luyten

Willem Jacob Luyten (born March 7, 1899 in Semarang , Indonesia , † November 21, 1994 in Minneapolis ) was a Dutch astronomer who lived and worked in the United States .

He played a decisive role in determining the mass-luminosity relationship of the stars , examined the proper motion of stars, discovered many white dwarfs and some of the sun's closest neighbors, such as Luyten's star . He worked at the Lick Observatory and Harvard College Observatory and taught at the University of Minnesota .

Life

Luytens ancestors came from the French Provence . The original family name Lutin goes back to lute players who lived at the Pope's court in Avignon in the 14th century and who later settled in Burgundy and finally the Netherlands.

Luyten's parents come from North Holland , but emigrated to Indonesia, which was a Dutch colony at the time . His father was a French teacher at the high school in Semarang, in the north of the island of Java . Willem Jacob was born here in 1899. In 1912 the family returned to the Netherlands.

Luyten's interest in astronomy grew in 1910 when Halley's Comet became visible in the night sky. He made his first observations in 1912 on Java. In the Netherlands he studied at the universities of Amsterdam and Leiden . In Leiden he was Ejnar Hertzsprung's first student . He received his doctorate in 1921, with his doctoral thesis based on the evaluation of the visual observation of 13,500 variable stars , which he had carried out with the 6- inch (15 cm) refractor at the Leiden Observatory . During his time in Leiden he was in contact with Jacobus Kapteyn , Willem de Sitter , Paul Ehrenfest and Albert Einstein .

In 1921 Luyten went to the USA, where he worked at the Lick Observatory for two years. In 1925, Harlow Shapley offered him a position at the Harvard College Observatory. Luyten worked for Harvard for seven years, the last two years in Bloemfontein , South Africa . In South Africa he met his future wife Willemina Miedema, with whom he was married for almost sixty years and had three children.

Although Luyten was interested in many of the areas of astronomy, he paid particular attention to the sizes and proper motion of the sun's neighboring stars . The fact that the stars were obviously unevenly distributed struck him as particularly striking. In the immediate vicinity of the sun (10 parsecs ) there are no red giants and only four luminous stars of spectral class A, although 99% of the stars visible to the naked eye are more luminous than the sun. He carried out exact measurements of proper movements, further developing Hertzsprung's thesis, according to which the absolute brightness and thus the distance can be inferred from the measure of the proper movement and the apparent brightness . While this method is not as accurate as determining parallax , it can be used with a large number of stars. He found that of the approximately 700 stars within 10 parsecs of the sun, about 96% are less luminous than this. From 1925 on, Luyten determined the proper motion of over 200,000 stars himself.

In 1927 a systematic survey of the sky, the "Bruce Proper Motion Survey", began. For this purpose, photo plates were evaluated that had been created between 1896 and 1910 with the 60 cm refractor (Bruce telescope) from Arequipa , Peru , and that depicted the entire southern sky. Stars up to the 17th magnitude were visible on over 1000 plates, each exposed for three hours . Luyten made over 300 photo plates from Bloemfontain, which he compared with the older plates using a blink comparator . 94,263 stars with significant proper movements were found. Most were brighter than the 14th magnitude and showed movements of up to 0.1 arc seconds per year. The evaluation took decades and the final star catalog was not published until 1963.

The survey revealed a multitude of white dwarfs that represent the final stages of relatively low-mass stars (like our Sun). In 1921 only three white dwarfs were known, in 1963 there were several hundred.

Luyten extended his investigations to the northern sky. Since the Bruce telescope was unsuitable for this because of its southern location, he initiated the "National Geographic / Palomar Observatory Sky Survey", using the 1.2 m Schmidt telescope of the Mount Palomar observatory . Instead of the laborious work with the blink comparator, the evaluation was carried out automatically using a special densitometer . This enabled the movement of more than 300,000 stars to be determined within a few years.

In 1967 Luyten retired. He has received numerous honors for his life's work. In 1925 he was elected to the American Academy of Arts and Sciences . In 1968 he received the Bruce Medal of the Astronomical Society of the Pacific , in 1970 he was admitted to the National Academy of Sciences .

The asteroid (1964) Luyten was named after him.

literature

• Willem J. Luyten: White dwarfs. Reidel, Dordrecht 1971, ISBN 90-277-0180-6
• Willem J. Luyten: The hyades. Univ. of Minnesota, Minneapolis 1971
• Willem J. Luyten, Anton E. La Bonte: The south galactic pole. Univ. of Minnesota, Minneapolis 1973
• Willem J. Luyten: The north galactic pole. Univ. of Minnesota, Minneapolis 1976

Web links

• Publications by WJ Luyten in the Astrophysics Data System
• Obituaries for WJ Luyten in the Astrophysics Data System
• Detailed biography
• Obituary, The New York Times November 26, 1994