Jesse L. Greenstein ’29, a pioneer in the field of astronomy whose insatiable passion for studying the galaxy compelled him to spend more than 1,000 hours in an observatory during his lifetime, died last Monday in California. He was 93.

Greenstein is remembered by his colleagues for his groundbreaking work on quasi-stellar objects, known as quasars, and White Dwarfs, which are remnants of destroyed stars. His advances provided evidence for the existence of black holes.

His love of astronomy also led him to determine many of the magnetic, nuclear and chemical properties of stars and galaxies.

Greenstein received his doctorate in 1937 from Harvard’s fledgling graduate astronomy department before receiving a grant to work at the University of Chicago. In 1948, Greenstein accepted a post at the California Institute of Technology (Caltech), where he helped to found its optical astronomy graduate program.

In the 1960s, at the apex of his career, Greenstein was a member of an advisory body that helped form the Harvard-Smithsonian Center for Astrophysics.

“It was very intoxicating and exciting to talk to Jesse because he was in touch with everything that was going on in astronomy,” said Robert P. Kirshner ’70, professor of astronomy and the assistant director of the Harvard-Smithsonian Center for Astrophysics. “He was a great, inspiring guy, and he was always very warm and encouraging.”

Greenstein was born in New York City in 1909. When he was eight-years-old, his grandfather gave him a brass telescope, which ignited his obsession with stars. As a child, he built his own astronomical equipment, including a spectroscope, an instrument used to examine wavelengths of light.

After attending the Horace Mann School for Boys, Greenstein entered Harvard at age 16. Following his graduation in 1929, Greenstein put astronomy on hold to work in his family’s real estate business, helping them through the early years of the Great Depression.

Greenstein returned to Harvard as a graduate student in 1934.

While at Harvard, Greenstein collaborated with former Harvard Astronomy Professor Fred L. Whipple on a paper that attempted to explain the origin of radio signals in outer space.

“He was a very fine astronomer,” said Whipple. “We were good friends when he was a graduate student.”

After receiving the National Research Council Fellowship grant in 1937, Greenstein started work at the University of Chicago’s Yerkes Laboratory. Two years later he joined the astrophysics department at the University of Chicago where, during World War II, he did research in optical design.

But it was during his years at Caltech that Greenstein made his most lasting contributions to the field of astronomy.

He founded the school’s graduate program in astronomy and spent more than 1,000 nights observing the skies from the Hale telescope at Caltech’s Palomar Observatory. He wrote, on average, eight and a half papers per year during his time at Caltech.

Along with his Caltech colleague Maartin Schmidt, Greenstein made significant strides in understanding quasars, the most distant stellar formations visible from the Earth.