born Dec. 20, 1876, Syria
died May 11, 1956, Pasadena, Calif., U.S.
Syrian-born U.S. astronomer.
He returned to the U.S. with his missionary parents when he was eight and studied at Dartmouth College, the University of Chicago, and the University of Munich. Using spectroscopy , he investigated sunspots and the rotation of the Sun, the velocities and distances of thousands of stars, and planetary atmospheres. In 1904 he joined the original staff of Mount Wilson Observatory , where he served as director (1923–46). He took an important part in planning the 200-in. (5-m) telescope for the Palomar Observatory .