John N. Bahcall





Born John Norris Bahcall, December 30, 1934, in Shreveport, LA; died of a rare blood disorder, August 17, 2005, in New York, NY. Astrophysicist and astronomer. Princeton astrophysicist John N. Bahcall is best known for his work concerning the creation of the Hubble Space Telescope. Launched in 1990 and still orbiting the earth, Hubble has helped scientists solve many of the universe's mysteries. In addition, Bahcall is credited with unlocking answers to several other cosmological puzzles, including the mystery of what makes the sun shine. Bahcall's research in the 1960s proved once and for all that the sun is fueled by nuclear reactions.

Bahcall was born on December 30, 1934, in Shreveport, Louisiana. He played tennis in high school and had no interest in science. When Bahcall enrolled at Louisiana State University, he decided to study philosophy, figuring he might become a rabbi. A year later, Bahcall transferred to the University of California at Berkeley, having never completed a science class in his life. At Berkeley, science was required, so he opted for physics. "It was the hardest thing I have ever done in my life, but I fell in love with science," Bahcall recalled during a 2002 commencement speech, according to Washington Post staffer Joe Holley. "I was thrilled by the fact that by knowing physics you could figure out how real things worked, like sunsets and airplanes, and that after a while everyone agreed on what was the right answer to a question." After the course, Bahcall decided to study physics and astronomy, choosing to rely on science—not spirituality—in his quest for greater truths.

Bahcall finished his undergraduate degree at UC Berkeley in 1956, then earned graduate degrees in physics, including a master's in 1957 from the University of Chicago and a doctorate from Harvard University, which he completed in 1961. Bahcall then worked as a research fellow at Indiana University and later joined the Kellogg Radiation Laboratory at the California Institute of Technology. While there, he worked on a series of calculations concerning the sun. Bahcall believed that the sun was probably powered by nuclear reactions, and he concluded that if so, the sun should be sending subatomic particles called neutrinos toward the earth along with its light.

He started working with astrophysicist Raymond Davis Jr. of the Brookhaven National Laboratory and the pair began what would become a decades-long collaboration. Together, they concocted an experiment to collect neutrinos. They built a neutrino detector, which was really an enormous tank filled with a chlorine-based cleaning fluid and sunk into the pit of an abandoned South Dakota gold mine. For the most part, the neutrinos passed through the tank undetected, just as they passed through all other matter, including the earth. Some neutrinos, however, collided with the chlorine atoms to create radioactive atoms. Periodically, Davis and Bahcall counted the radioactive atoms.

In 1968 they reported their experiment to the scientific world, noting that they had been able to capture and study neutrinos from the sun, thus proving that the sun's light is derived from nuclear reactions. The mystery of how the sun shines had puzzled scientists for decades—and Bahcall's investigation settled the matter.

That same year, Bahcall joined the Institute for Advanced Study at Princeton University. There, he continued his investigations with neutrinos and also studied the dark matter of the universe and the evolution of stars. By 1971, he was a full faculty member—a professor of natural resources. He trained batches of astrophysicists, many of whom became leaders in the field.

Bahcall spread his passion around the globe, traveling abroad to help launch astronomy groups at Tel Aviv University and the Weizmann Institute of Science, both in Israel. During one of these trips, he met Israeli graduate student Neta Assaf. Bahcall asked her out more than ten times before she accepted a date. Though Bahcall could not speak Hebrew and Assaf was not fluent in English, their relationship flourished and they married within a year. After relocating to the United States with her new husband, Neta Bahcall became a cosmologist at Princeton. They hold the distinction of being the only astronomy couple each with memberships to the National Academy of Sciences.

By the 1970s, Bahcall had started working with Princeton astronomer Lyman Spitzer Jr. to advocate for the development of a space telescope. Spitzer had proposed the idea of a space telescope back in the 1940s but the project did not seem viable until the 1970s when technology had advanced. Bahcall and Spitzer made numerous appearances before Congress and, after winning approval, worked on the Hubble Space Telescope's development. It was finally launched in 1990 by the space shuttle Discovery and put into orbit 370 miles above the earth. Since then, the telescope has been making daily observations of space free from the distractions imposed by the earth's atmosphere.

Speaking to the Los Angeles Times shortly after Bahcall's death, Caltech astronomer Maarten Schmidt recalled Bahcall as a "tenacious" creature who would never give up on an idea "and it really paid off with the Hubble Space Telescope." Bahcall remained loyal to the instrument to the end. When former National Aeronautics and Space Administration (NASA) administrator Sean O'Keefe announced that there would be no more shuttle missions to repair the telescope following the 2003 explosion of the shuttle Columbia, Bahcall put up a fight. He penned editorials and made calls on the telescope's behalf from his hospital bed as he lay dying. Eventually, NASA agreed to reconsider.

In 2002, Raymond Davis—the man Bahcall had done his neutrino collaboration with—earned the Nobel Prize in Physics for his investigations into neutrinos. Davis shared the award with University of Tokyo professor Masatoshi Koshiba, who had also worked on neutrino detection. Many physicists believed Bahcall should have been honored as well, but he never complained. Bahcall did receive numerous awards over his lifetime, including NASA's Distinguished Public Service Medal in 1992 for his work with the Hubble Space Telescope. Bahcall also received the National Medal of Science in 1998. Over the course of his career, Bahcall wrote more than 500 scientific papers and published five books related to astrophysics, astronomy, and neutrinos. His writings helped other scientists better understand the cosmos.

Bahcall died of a rare blood disorder on August 17, 2005, at New York-Presbyterian/Weill Cornell Hospital. He was 70. Survivors include his wife, sons Safi and Dan, his daughter, Orli, and his brother, Robert. Sources: Los Angeles Times, August 20, 2005, p. B16; New York Times, August 19, 2005, p. C14; Times (London, England), September 1, 2005, p. 68; Washington Post, August 20, 2005, p. B6.

Lisa Frick



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