Osterbrock, the former director of the Lick Observatory, collapsed while strolling across the UC Santa Cruz campus Thursday. Paramedics arrived within minutes but were unable to save him, according to campus spokesman Tim Stephens. The cause of death has not been determined.

Osterbrock's book, "The Astrophysics of Gaseous Nebulae and Active Galactic Nuclei," has become a standard textbook for student astronomers the world over, according to [Joseph Miller]. Osterbrock retired in 1992, but continued to work in his campus office.

Osterbrock was born and raised in Cincinnati and earned his doctorate in astronomy from the University of Chicago. He came to UC Santa Cruz in 1972 after holding faculty positions at Caltech and the University of Wisconsin. He served as director of the Lick Observatory on Mt. Hamilton east of San Jose from 1973 to 1981.