Tuesday, October 8, 2002

3 Physicists Share Nobel Prize for Work on Cosmic Neutrinos and X-Rays By RICHARD MONASTERSKY Three scientists have won the Nobel Prize in Physics for exploring some of the most violent and the most subtle aspects of the universe. Working independently, the researchers pioneered ways to observe X-rays and the wraithlike particles known as neutrinos coming from space. Riccardo Giacconi, director of Associated Universities Inc., in Washington, D.C., will receive half of the prize, which is worth a total of $1.08-million, for developing the first methods to detect X-rays from outside our solar system. The other half will be shared by Raymond Davis Jr., a professor emeritus of physics and astronomy at the University of Pennsylvania, and by Masatoshi Koshiba, a professor emeritus at the University of Tokyo's International Center for Elementary Particle Physics. They constructed the first detectors capable of capturing the elusive neutrinos coming from the sun and more-distant stars. Mr. Giacconi started his X-ray search at the age of 28, in 1959, when he helped design a detector that could capture the extremely energetic photons. In the 1960s, he and colleagues launched those detectors on rockets to get above the earth's atmosphere, which absorbs all X-rays from space. He then began construction of Uhuru, a satellite carrying an X-ray sensor, which was launched in 1970. He designed a second satellite mission, the Einstein X-Ray Observatory, which flew in 1978, and started work on a third satellite, which eventually took off in 1999 as the Chandra X-Ray Observatory. The satellite observatories have given astronomers insights into processes that take place in explosive bursts, such as the blastlike death of stars into supernovas and the voracious consumption of matter by black holes. The citation by the Royal Swedish Academy of Sciences states: "A new, fantastic zoo of important and strange celestial bodies has been discovered and studied. Today the universe seems much more remarkable than we believed 50 years ago -- in no small part thanks to X-ray astronomy." Mr. Davis won his share of the prize for hunting the sun's neutrinos, particles that interact so skittishly with normal matter that trillions zoom through our bodies every second without touching any atom. To capture such particles, Mr. Davis had a tank with more than 600 tons of dry-cleaning fluid installed nearly a mile below ground in a gold mine. Neutrinos from the sun occasionally hit a chlorine atom in the fluid and formed atoms of argon, which Mr. Davis detected and used to measure the amount of solar neutrinos. The Swedish Academy called that experiment "an achievement considerably more difficult than finding a particular grain of sand in the whole of the Sahara." Mr. Koshiba developed a different type of underground detector, a gigantic tank filled with ultrapure water. Neutrinos passing through the tank rarely interacted with the water, producing flashes of light that were captured by banks of instruments on the sides of the tank. He designed an even larger tank, called Super Kamiokande, which began observations in 1996. That detector provided the first evidence that neutrinos alter their form, switching from one type of neutrino to another. Such transformations indicate that neutrinos are not massless, as had long been thought, but carry a small mass -- a result "which is of great significance for the Standard Model of elementary particles and also for the role that neutrinos play in the universe," said the Swedish Academy. The text of the Nobel announcement is available on the Nobel Foundation's World Wide Web site. Background articles from The Chronicle: Proof That Neutrinos Have Mass Sparks a Revolution in Physics (12/18/1998) X-Ray Eyes: Orbiting Telescope Helps Scientists Probe Some of the Darkest Objects in the Universe (9/21/2001) Other news of 2002 Nobel Prizes: Nobel Prize in Medicine Goes to 3 Scientists Who Study Cell Death (10/7/2002) Easy-to-print version E-mail this article

More than 300 college presidents sign statement condemning anti-Semitism Students on more than 30 campuses protest against threatened war with Iraq 3 physicists share Nobel Prize for work on cosmic neutrinos and X-rays Feud erupts between 2 Catholic higher-education groups over approaches to student life U.S. House panel proposes a record $5.4-billion budget for NSF TIAA-CREF chooses former Merrill Lynch executive as its new leader Physicist who runs university in India is accused of plagiarizing Stanford professor Congress eases copyright restrictions on distance education Agreement on Webcast fees won't help college radio stations