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Subject: Jesse Greenstein, 93, Mentor to Astronomers

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[ Next Thread | Previous Thread | Next Message | Previous Message ] Date Posted: October 26, 2002 7:25:01 EDT In reply to: catching up 's message, "Norbert Schultze, German Composer" on October 26, 2002 7:12:39 EDT Jesse L. Greenstein, who helped explain astronomical exotica like unimaginably bright beacons at the edge of the universe and hot cinders of burned-out stars, died on Monday in Arcadia, Calif. He was 93. Dr. Greenstein also mentored a generation of astronomers, sometimes referring to himself as "a metapapa." "He was the father figure for many of us," said Dr. Marshall H. Cohen, an emeritus professor of astronomy at the California Institute of Technology. Over his career which spanned more than a half-century, Dr. Greenstein's research helped alter astronomers' view of the universe from that of a placid, unchanging tapestry of twinkling stars to something in constant, violent turmoil, filled with strange objects with names like quasars and white dwarfs. When Dr. Greenstein began his academic career in 1937 after completing his Ph.D. at Harvard, astronomy consisted of what could be seen through optical telescopes: stars and galaxies. That year, he and Dr. Fred Whipple of Harvard wrote one of the first scientific papers to offer a detailed explanation for the origin of radio signals from outer space. Although the explanation turned out to be incorrect, "that paper essentially proved that the sky was not this quiet, tranquil place everyone thought," Dr. Cohen said. "That was a forerunner of what became the violent universe. He was one of the people who appreciated this from the very beginning." Dr. Greenstein's research was rich and broad. He measured the elemental makeup of stars, finding that they varied considerably, some rich in carbon, others heavier in other atoms. Working with physicists, he helped explain how nuclear reactions within stars could produce all of the naturally occurring elements. Dr. Greenstein also explained how the vibrations of electric and magnetic fields in light from distant stars, which point in random directions when they are emitted, become partly lined up by the time they reach Earth. He and a colleague, Dr. Leverett Davis Jr., postulated that even in the dark voids of interstellar space, weak magnetic fields cause iron-containing dust particles to spin like tiny hypercharged windmills. Light bouncing off the grains then becomes lined up, or polarized. In 1963, astronomers discovered that objects they had thought were strange stars within the galaxy — they called them quasars, short for quasi-stellar objects — were actually the most distant objects in the universe. Dr. Greenstein, along with Dr. Maarten Schmidt, also of Caltech, showed that quasars could not be diffuse galaxy-size objects, but are much more compact. They concluded, rightly as it seems now, that the energy source that could spew out that much light could only be tremendous amounts of matter pouring into what is now called a black hole. That paper appeared in a compendium, published in 2000, of the 53 most important papers from The Astrophysical Journal and The Astronomical Journal in the 20th century. Dr. Greenstein also cataloged hundreds of remnants of stars that had exhausted their hydrogen fuel, known as white dwarfs. Jesse Leonard Greenstein was born in New York City in 1909. He went to Harvard at 16. After completing his master's degree in astronomy there in 1930, he returned to New York City to help with his father's real estate business. "It was his duty," said William T. Golden, a longtime treasurer for the American Association for the Advancement of Science and a boyhood friend of Dr. Greenstein. "It was not the kind of thing he liked at all." After four years in real estate, he quit and returned to Harvard. After earning his doctorate he worked at the Yerkes Observatory in Williams Bay, Wis., then moved to the University of Chicago and became an instructor and later a professor. In 1948, he became the founding member of the astronomy department at Caltech. In that first year, he taught all of the astrophysics classes himself. He retired from Caltech in 1979. Dr. Greenstein was elected to the National Academy of Sciences in 1957. His awards include the NASA Distinguished Public Service Medal in 1974 and the Gold Medal of the Royal Astronomical Society in 1975. His wife, Naomi, whom he met as an undergraduate at Harvard, died this year. They lived in Duarte, Calif. He is survived by two sons, Peter, of Oakland, Calif., and George, of Amherst, Mass.; and a granddaughter. [ Next Thread | Previous Thread | Next Message | Previous Message ]