Robert Julius Trumpler

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Robert Julius Trumpler (October 2, 1886 – September 10, 1956, Berkeley, California) was a Swiss-American astronomer. He was born in Zürich, Switzerland, entered Universität Zürich but later transferred to University of Göttingen where he earned his Ph.D. in 1910. In 1915, during World War I he emigrated to the United States, and joined the University of California. He took a position at Allegheny Observatory, and later went to Lick Observatory. In 1921, he became a naturalized citizen of the United States. He was elected a member of the United States National Academy of Sciences in 1932.[1]

He is most noted for observing that the brightness of the more distant open clusters was lower than expected, and the stars appeared more red. This was explained by the interstellar dust scattered through the galaxy, resulting in the absorption (extinction) of light or interstellar extinction of light.^[1]

Trumpler further studied and catalogued open clusters in order to determine the size of the Milky Way galaxy. At first he thought his analysis placed an upper limit on the Milky Way's diameter of about 10,000 parsecs with the Sun located somewhat near the center although he later revised this. While catalogueing open clusters he also devised a system for their classification by according them designations for their central concentration, the range of brightness of their individual stars and the number of stars in the cluster. This system of classifying open clusters, called the Trumpler classification,^[2] is still in use today.

The Robert J. Trumpler Award, awarded by the Astronomical Society of the Pacific for an outstanding PhD Thesis in austronomy, is named in his honor.^[3]

[edit] Honors

The following celestial features are named after him:

• The crater Trumpler on the Moon.
• A crater on Mars.

[edit] Publications

1. R.J. Trumpler, 1930. Preliminary results on the distances, dimensions and space distribution of open star clusters. Lick Obs. Bull. Vol XIV, No. 420 (1930) 154-188. Table 16 is the Trumpler catalog of open clusters, referred to as "Trumpler (or Tr) 1-37

[edit] References

• National Academy of Sciences biography - Biographical Memoirs V.78 (2000) pp. 276–297
• The Munich Astro Archive – Robert Julius Trumpler (October 2, 1886 - September 10, 1956)
• The Interstellar Medium: Dust
• "LAUDS ASTRONOMY ON '35 DISCOVERIES; Dr. Shapley Lists Outstanding Developments of the Year in a Talk at Cambridge.". The New York Times: pp. Page 24. October 20, 1935. http://select.nytimes.com/gst/abstract.html?res=F10612FB3C5B1B7B93C2AB178BD95F418385F9&scp=1&sq=Julius%20Trumpler&st=cse. Retrieved on 2008-09-05. "... perhaps, among the high lights of 1935 the preliminary results announced by Trumpler (Dr. Robert Julius Trumpler) of the Lick Observatory on his test of ..."