R.I.P. John M. Bahcall

[Xjmt]

From today's NYTIMES:

August 19, 2005
John N. Bahcall, 70, Dies; Astrophysicist at Princeton
By DENNIS OVERBYE
John N. Bahcall, an astrophysicist who helped prove what makes the sun shine and worked behind the scenes in Washington for more than three decades to help ensure the construction and survival of the Hubble Space Telescope, died on Wednesday at NewYork-Presbyterian/Weill Cornell hospital. He was 70.

The cause was a rare blood disorder, his family said.

A professor for 35 years at the Institute for Advanced Study in Princeton, N.J., Dr. Bahcall was one of the scientific brahmins of his time, leading numerous influential committees and organizations, including the American Physical Society and the American Astronomical Society, and advising NASA and Congress.

He led the National Academy of Sciences panel that produced an influential report in 1990 laying out what should be done in the next decade of astronomy. In 1964, Dr. Bahcall and Raymond Davis, of the Brookhaven National Laboratory, began a lifelong collaboration when they suggested testing theories of what happens inside the sun by measuring the flow of subatomic particles called neutrinos, produced by its nuclear reactions.

When Dr. Davis's detector, a tank of cleaning fluid in an old gold mine in Lead, S.D., failed to see as many neutrinos as Dr. Bahcall's model had predicted, few physicists took the discrepancy seriously.

But Dr. Bahcall trumpeted the results to his colleagues, urging them to investigate the solar neutrino problem as an issue in fundamental physics.

The result was "a scientific gold mine for both astronomy and physics," said Michael S. Turner, a cosmologist at the University of Chicago and the assistant director of the National Science Foundation. It led to the birth of neutrino astronomy, the detection of these particles from a supernova explosion in 1987, and the discovery that these strange particles, once thought massless, have a tiny mass and can change form as they fly along.

That changing of form, it turned out, according to experiments in Japan, Canada, Italy and Russia, allowed the solar neutrinos to elude detection in South Dakota. Referring to it, John G. Learned, a neutrino physicist at the University of Hawaii, said in an e-mail message, "We now know that the trouble was with the slippery shape-shifting neutrinos, and John B. had it right."

Along the way, as Dr. Bahcall never tired of pointing out, one of the enduring mysteries of modern science had been solved. "The nuclear reactions that produce the neutrinos also cause the sun to shine," he wrote in an article in 1996.

In 2002, Dr. Davis and Masatoshi Koshiba of the University of Tokyo shared the Nobel Prize in Physics for neutrino work, a prize some physicists thought Dr. Bahcall should also have shared. If he was disappointed he did not show it. "He only had generous words for Ray Davis and Koshiba," Dr. Turner said.

John Norris Bahcall was born in Shreveport, La., on Dec. 30, 1934. He enrolled at Louisiana State University intending to study philosophy and perhaps become a rabbi, but then decided on science and transferred to the University of California, Berkeley, where he graduated in 1956 with a degree in physics.

After emerging from Harvard with a Ph.D. in 1961, he took a research position at Indiana University to work with Emil Konopinski, an expert on the so-called weak force that governs some types of radioactive decay. Among the products of the weak force are neutrinos, which play a crucial role in nuclear reactions in stars.

Dr. Bahcall's interest in such interactions got him an invitation to the California Institute of Technology to work with William A. Fowler, an expert in the field. While he was there, he suggested the solar neutrino experiment.

Turning his attention much farther outward, he and Edwin E. Salpeter of Cornell suggested in 1965 that quasars, brilliant explosions billions of light-years away, could be used as searchlights by studying the intervening gulfs of time and space.

By studying which wavelengths of light were absorbed as the quasar radiation passed through clouds of gas on its way here, they said, astronomers could ascertain the temperatures, densities and compositions of remote regions of the cosmos.

When the Hubble Space Telescope flew a quarter-century later, a substantial fraction of the telescope's time was allocated to such studies, with Dr. Bahcall as the principal investigator.

About the same time, on a trip to Israel, he was introduced to a young physics graduate student, Neta Assaf, to whom he took a liking, even though he spoke no Hebrew and she, little English. After a dozen rejections, he got a date with her. Within a year they were married.

"The persistence and never giving up was a theme for my dad," said his older son, Safi Bahcall, in an e-mail message. "Solar neutrinos were just one example."

The Hubble Space Telescope was another beneficiary of that persistence. The idea of putting a telescope in space, where it would be unencumbered by the atmosphere, was first proposed by the Princeton astronomer Lyman Spitzer Jr. in 1946. But it was 44 years of delays, cancellations, bargaining and lobbying before the telescope was finally launched from the space shuttle in 1990.

Any time there was trouble, "Lyman Spitzer and John would put on their sincere suits and go down to Washington," recalled James Peebles, a Princeton cosmologist.

Maarten Schmidt, a Caltech astronomer said, "It was John, I thought, who for years kept up the advocacy in a very effective way."

Dr. Bahcall recently said that some scientists initially opposed launching the telescope with the shuttle, recalling the time in the 1970's that a prominent physicist had driven to Princeton to persuade him and Dr. Spitzer not to go along with it. NASA, however, had another idea. "In the end we played ball," Dr. Bahcall said.

The advocacy continued to the end. Dr. Bahcall was upset when, after the Columbia disaster, NASA's previous administrator, Sean O'Keefe, ruled out any more shuttle missions to refurbish the orbiting observatory, condemning it, in effect, to an early demise.

Dr. Bahcall was cheered when a National Academy of Sciences report a year ago rejected Mr. O'Keefe's reasoning and endorsed an astronaut mission instead of a robotic one as the best way to keep the Hubble flying. "Finally, somebody told the king he didn't have any clothes," Dr. Bahcall said at the time.

The present administrator, Michael Griffin, has said he will re-examine the issue.

John M. Grunsfeld, an astronaut who has worked on the Hubble and was once NASA's chief scientist, said in an e-mail message from Moscow, "John and I had quite a bit of communication regarding H.S.T., and I consider that he played a pivotal role in keeping the flame of H.S.T. alive through the events of the last year and a half."

Even in the hospital, Dr. Bahcall was making calls about his beloved Hubble and other scientific matters, said his wife, Neta A. Bahcall, a cosmologist at Princeton.

In addition to his wife and his son Safi, he is survived by his daughter, Orli, of New York; a son, Dan, of Berkeley, Calif.; and a brother, Robert, of Baton Rouge, La.

Dr. Bahcall summarized his beliefs about scientific discovery when the Hubble was launched. "We often frame our understanding of what the Space Telescope will do in terms of what we expect to find," he said then, "and actually it would be terribly anticlimactic if in fact we found what we expect to find.

"The most important discoveries will provide answers to questions that we do not yet know how to ask and will concern objects we have not yet imagined."



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[Henry J]

Re "and actually it would be terribly anticlimactic if in fact we found what we expect to find."
Well put!

Re "urging them to investigate the solar neutrino problem as an issue in fundamental physics. "
As Mr. Spock might say - fascinating.

Re ""We now know that the trouble was with the slippery shape-shifting neutrinos, and John B. had it right." "
As long as none of them are from the Delta quadrant...

Re "The Hubble Space Telescope was another beneficiary of that persistence."




Henry