September 13, 1912–August 29, 200

BY GEORGE W. PRESTON

HORACE BABCOCK’S CAREER at the Mount Wilson and Palomar (later, Hale) Observatories spanned more than three decades. During the first 18 years, from 1946 to 1964, he pioneered the measurement of magnetic fields in stars more massive than the sun, produced a famously successful model of the 22-year cycle of solar activity, and invented important instruments and techniques that are employed throughout the world to this day. Upon assuming the directorship of the observatories, he devoted his last 14 years to creating one of the world’s premier astronomical observatories at Las Campanas in the foothills of the Chilean Andes.

Horace Babcock was born in Pasadena, California, the only child of Harold and Mary Babcock. Harold met Horace’s mother, Mary Henderson, in Berkeley during his student days at the College of Electrical Engineering, University of California. After brief appointments as a laboratory assistant at the National Bureau of Standards in 1906 and as a physics teacher at the University of California, Berkeley, in 1907, Horace’s father was invited by George Ellery Hale in 1908 to join the staff of the Mount Wilson Observatory (MWO), where he remained for the rest of his career. (Harold