Robert Julius Trumpler

Robert Julius Trumpler ( until 1915 Robert Trumpler, born October 2, 1886 in Zurich, Switzerland, † September 10, 1956 in Berkeley, California ) was a native of Switzerland, American astronomer.

In 1915 Trumpler went to the U.S. to accept a position at the Allegheny Observatory. Later he went to the Lick Observatory. In 1921 he became a U.S. citizen. In 1938 he became professor at the University of California, Berkeley, where he remained until his retirement in 1951. Thereafter he lived in Rio del Mar.

Trumpler is known primarily for his classification of open star clusters and for the discovery of the phenomenon of light absorption by interstellar dust. A Martian craters and a lunar crater have been named after him.