La Serena, Chile – Carnegie astronomer Mark Phillips will share the 2007 Cosmology Prize of the Peter and Patricia Gruber Foundation for his role in discovering that the universe is expanding at an accelerating rate.
Phillips was one of twenty members of the High-z Supernova Search Team,* which looked for distant type Ia supernovae—violent explosions of white dwarfs, the remnants of stars that have exhausted their nuclear fuel. Because the supernovae are extremely bright and similar to each other, they can be used as cosmological “standard candles” for accurately measuring distances to galaxies halfway across the universe. The High-z team revealed the universe’s accelerating behavior by measuring the expansion rate of the universe over time, using distant and nearby type Ia supernovae.
“The Carnegie Institution salutes Dr. Phillips for the insight his contributions have provided regarding the fundamental nature of the universe,” said President Richard A. Meserve. “We are very proud of his accomplishments.”
Phillips, who aided in the discovery while at the Cerro Tololo Inter-American Observatory (CTIO) in Chile, moved to Carnegie from CTIO in 1998. Phillips was a pioneer in demonstrating that type Ia supernovae could be used as precise cosmological standard candles; with colleagues, he established the techniques used for discovering and measuring distances to these objects.
As an ambulance drives away, the sound waves from its siren spread out behind it in a phenomenon known as the Doppler effect; the increased wavelength is perceived as a lower pitch. Similarly, when light-emitting objects move away, wavelengths of light lengthen, resulting in a redder color. This “redshift” allows scientists to measure how quickly celestial objects are moving away from us and, from that, establish how quickly the universe is expanding. This rate of expansion observed today—known as the Hubble Constant—is a critical component to calculating the age and size of the universe.
Phillips’ work in determining accurate distances to type Ia supernovae allowed the High-z Supernova Search Team to measure how the Hubble constant has evolved since the universe was half its present age. If dominated by gravity, the universe would be decelerating. Yet Phillips and colleagues discovered, to their amazement, that the expansion rate is currently accelerating. The team’s findings were independently confirmed by the Supernova Cosmology Project.**
Some propose that an unseen force called “dark energy” is driving the acceleration; others interpret it as a failure of Einstein’s theory of general relativity. Whatever the explanation, the implications for modern physics are profound.
“I am delighted to know that Mark will share the 2007 Gruber Prize. He has played a seminal role in turning supernovae into precise tools for cosmology, a critical ingredient in the discovery of the accelerating universe,” remarked Wendy Freedman, director of the Carnegie Observatories.
The Gruber Cosmology Prize is awarded annually to honor those scientists who make discoveries that alter perceptions and comprehension of the universe. The $500,000 prize will be presented to Phillips and colleagues in a ceremony at the University of Cambridge on September 7. Two other Carnegie astronomers have held the honor: the Department of Terrestrial Magnetism’s Vera Rubin received the prize in 2002 for her work on dark matter in the universe and her exploration of the rotation of spiral galaxies. In 2000, Allan Sandage, Staff Astronomer Emeritus at the Carnegie Observatories, shared the first Gruber Prize for Cosmology for his achievements in observational cosmology.
Phillips, a California native, received a Bachelor’s degree in Astronomy from San Diego State University in 1973 and a Ph.D. in Astronomy from the University of California at Santa Cruz in 1977. Since 1998, Phillips has been associate director at Carnegie’s Las Campanas Observatory in Chile, where he continues to extend the applications of Ia supernovae and is refining measurements of the nature of dark energy.
The team members jointly recognized by the Gruber Foundation are:
*The High-z Supernova Search team: Brian Schmidt and his team from the USA, UK, Germany, Chile and Australia: Peter Challis, Harvard University; Alejandro Clocchiatt, Pontificia Universidad Católica de Chile; Alan Diercks, Institute for Systems Biology, Seattle; Alexei V. Filippenko, University of California, Berkeley; Peter M. Garnavich, University of Notre Dame; Ronald L. Gilliland, Space Telescope Science Institute; Craig J. Hogan, University of Washington; Saurabh Jha, Stanford Linear Accelerator Center; Robert P. Kirshner, Harvard University; Bruno Leibundgut, European Southern Observatory; Mark M. Phillips, Carnegie Observatories; David Reiss, Institute for Systems Biology. Seattle; Adam G. Riess, Space Telescope Science Institute; Robert A. Schommer (Deceased); R. Chris Smith, Cerro Tololo Inter-American Observatory, Chile; Jason Spyromilio, European Southern Observatory; Christopher Stubbs, Harvard University; Nicholas B. Suntzeff, Texas A&M University; John L. Tonry, Institute for Astronomy, Honolulu.
**Saul Perlmutter and the Supernova Cosmology Project team from Australia, Chile, France, Spain, Sweden, UK and USA: Gregory Aldering, E. O. Lawrence Berkeley National Laboratory; Brian J. Boyle, Australia Telescope National Facility; Patricia G. Castro, University of Edinburgh; Warrick Couch, University of New South Wales; Susana Deustua, American Astronomical Society; Richard Ellis, California Institute of Technology; Sebastien Fabbro, Instituto Superior Técnico, Lisbon; Alexei Filippenko, University of California, Berkeley (also a member of the High-z team); Andrew Fruchter, Space Telescope Science Institute; Gerson Goldhaber, Lawrence Berkeley National Laboratory; Ariel Goobar, University of Stockholm; Donald Groom, Lawrence Berkeley National Laboratory; Isobel Hook, Oxford University; Mike Irwin, University of Cambridge; Alex Kim, Lawrence Berkeley National Laboratory; Matthew Kim; Robert Knop, Vanderbilt University; Julia C. Lee, Harvard-Smithsonian Center for Astrophysics; Chris Lidman, European Southern Observatory; Richard McMahon, University of Cambridge; Thomas Matheson, NOAO Gemini Science Center; Heidi Newberg, Rensselaer Polytechnic Institute; Peter Nugent, Lawrence Berkeley National Laboratory; Nelson Nunes, University of Cambridge; Reynald Pain, University Paris VI & VII; Nino Panagia, Space Telescope Science Institute.
The Carnegie Institution of Washington (www.carnegieinstitution.org), a private nonprofit organization, has been a pioneering force in basic scientific research since 1902. It has six research departments: the Geophysical Laboratory and the Department of Terrestrial Magnetism, both located in Washington, D.C.; The Observatories, in Pasadena, California, and Chile; the Department of Plant Biology and the Department of Global Ecology, in Stanford, California; and the Department of Embryology, in Baltimore, Maryland.