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August 15, 2006

Cosmic Background Explorer (COBE) Team Wins Gruber Prize

BERKELEY, CA — John Mather, Project Scientist of NASA's Cosmic Background Explorer satellite mission, and eighteen members of COBE's Science Working Group, including George Smoot of the Department of Energy's Lawrence Berkeley National Laboratory, have jointly received the 2006 Gruber Cosmology Prize for their ground-breaking studies of the cosmic microwave background (CMB). The COBE experiments not only confirmed that the universe was born in a big bang but shed light on its subsequent structure.

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Astrophysicist George Smoot

The Gruber Prize was awarded at the opening ceremony of the International Astronomical Union's General Assembly in Prague on Tuesday, August 15. In response to news of the prize, Smoot said, "We are pleased that the work and results of the COBE scientists, engineers, and staff are being honored by the Gruber Foundation. It was such a pleasure first to participate in COBE's discoveries, and then again to have them recognized."

Smoot is a member of Berkeley Lab's Physics Division and a professor of physics at the University of California at Berkeley. He became interested in cosmology while at MIT, where he received his Ph.D. in 1970. After he joined UC Berkeley he continued to pursue questions in astrophysics and realized that the relic radiation from the big bang would be a unique and useful tool to probe cosmology.

The CMB is the remnant of radiation that has filled the universe since the moment, some 300,000 years after the big bang, when the universe cooled enough for protons and electrons to form hydrogen atoms -- freeing photons from what had been a hot primordial soup of subatomic particles. Ever since that time these energetic photons have been traveling through space, their wavelength now stretched to microwave scale and their frequency reduced to the equivalent of radiation from a black body at only 2.73 degrees Kelvin.

Among the CMB's most interesting features are minute variations in its temperature in different parts of the sky. Smoot proposed that differential microwave radiometers (DMRs) be carried aboard a satellite to map these differences. His proposal and those of other investigators were combined in the COBE experiment, NASA's first dedicated cosmology mission, which after many setbacks was finally launched late in 1989. The experiments aboard COBE included three DMRs, with Smoot as principal investigator, a far infrared absolute spectrophotometer (FIRAS), with John Mather as PI, and the diffuse infrared background experiment (DIRBE), with Michael Hauser as PI.

After years of data analysis, COBE's results confirmed that the cosmic microwave background had indeed originated in the big bang and, from the DMR data, revealed tiny but regular temperature fluctuations, or "wrinkles" in its structure. Variations in the CMB are now recognized as the seeds of the intricate large-scale structures that exist everywhere in the cosmos.

In subsequent years, ever finer measurements of the CMB from balloon-borne experiments like BOOMERANG and MAXIMA and from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) have yielded new information about the history of the universe, the evolution of its structures, and even what unknown "stuff" it contains, including mysterious dark matter and dark energy. Many of these projects have been supported by the Department of Energy's Office of Science, as well as by NASA and the National Science Foundation.

spacer image COBE satellite
Of the three experiments aboard the COBE satellite, George Smoot was principal investigator of the differential microwave radiometer (DMR) experiment, which used three DMRs to measure minute temperature differences in the cosmic microwave background.

All subsequent CMB studies owe much to COBE, which revealed that the universe is filled with diffuse infrared radiation from previously unknown galaxies and proved that the universe indeed began in a hot big bang, from which evolved a dense, almost uniform soup containing weak fluctuations that grew into today's galaxies and stars.

The Gruber Cosmology Prize consists of a gold medal and $250,000 in cash, half of which is awarded to Mather, with the rest divided by COBE Science Working Group members Charles Bennett, Nancy Boggess, Edward Cheng, Eli Dwek, Samuel Gulkis, Michael Hauser, Michael Janssen, Thomas Kelsall, Philip Lubin, Stephan Meyer, S. Harvey Moseley, Thomas Murdock, Richard Shafer, Robert Silverberg, George Smoot, Rainer Weiss, the estate of David Wilkinson (deceased), and Edward Wright.

The Peter Gruber Foundation, based in the Virgin Islands, supports five international awards, in Cosmology, Justice, Genetics, Neuroscience, and Women's Rights.

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