Pasadena, CA—The Peter and Patricia Gruber Foundation awarded the 2009 Cosmology Prize to Carnegie’s Wendy Freedman; Robert Kennicutt of the Institute of Astronomy at the University of Cambridge; and Jeremy Mould at the University of Melbourne School of Physics. The prize is for their work defining the Hubble constant—the rate at which the universe is expanding.

The three investigators led an international team of astronomers on the Hubble Space Telescope (HST) Key Project to provide the definitive measurement of the Hubble constant. The Hubble constant is needed to determine the age of the universe and it underpins every other basic cosmological measurement.

Freedman is the Crawford H. Greenewalt Chair, director of the Carnegie Observatories. She was chosen as the scientific leader for the Key Project for her years of developing innovative techniques and technologies and her management style. She refined measurements of pulsating stars called Cepheid variables used as “standard candles” to measure extragalactic distances. Freedman developed schemes to determine distances to Cepheids, correcting for the obscuring effects from interstellar dust. On the Key Project, her team searched for Cepheids in nearby galaxies. It took over ten years and culminated with the calculation of the Hubble constant at 72  kilometers per second per megaparsec (km/sec/Mpc). The number yields an estimate of the age of the universe, accepted everywhere, at 13.7 billion years.

“Wendy Freedman is an outstanding scientist and an inspired leader,” remarked Carnegie president Richard A. Meserve. “At a very early stage in her career she produced a body of work that is recognized worldwide for its impact and importance. We are very proud of her accomplishments and of the recognition of them as reflected in this prestigious award.”

One of the most important implications of the research is its contribution to the understanding of dark energy—the force that is accelerating the expansion rate of the universe. Einstein’s equations contained a cosmological constant. If the constant is ignored, there is a contradiction between the age of the universe that Freedman established and the ages of the oldest stars. The concept of dark energy solves the dilemma. Freedman now observes distant supernovae, also standard candles, to understand the cosmic acceleration caused by dark energy.   

In addition to leading the Carnegie Observatories, Freedman is chair of the Giant Magellan Telescope Corporation Board, which is designing and constructing a 25-meter optical telescope. She is a Fellow of the American Association of Arts & Sciences and a Fellow of the American Philosophical Society. She was elected to the National Academy of Sciences in 2004. Freedman will receive the prize at the annual meeting of the International Astronomical Union in Rio de Janeiro, Brazil, on August 4, 2009. Other Carnegie recipients of the Cosmology Prize include Allan Sandage (2000), Vera Rubin (2002) and a team, which included Mark Phillips (2007).

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