Brian Schmidt (Australian National University) and the High-z Supernova Search team have been awarded the 2007 Gruber Cosmology Prize for their discovery that the universe's expansion is accelerating under the influence of dark energy. They will share the honor with Saul Perlmutter (University of California at Berkeley) and the Supernova Cosmology Project, a second team of astronomers who also observed the accelerating expansion.
“The Gruber Prize is a great honor reflecting on the work done by more than 20 people over a decade,” said Schmidt. “When I look at the previous winners of the award, I feel humbled, but it shows the strength of a team working together.”
Eleven of the 19 members of the High-z Supernova Search Term are or previously were affiliated with Harvard University. Clowes Professor of Science Robert Kirshner, leader of the Harvard supernova group since 1986, worked with all of them.
“I am especially proud because so many of the people being recognized by this award are my Ph.D. students, postdocs, and co-workers here at Harvard,” enthused Kirshner. “Brian Schmidt, Adam Riess, Saurabh Jha, and Chris Smith were all terrific students. Bruno Leibundgut, Peter Garnavich, and Peter Challis have been great staff members, and Chris Stubbs has been a great catch for Harvard’s faculty.”
Harvard University graduates Craig Hogan and John Tonry round out the list of Harvard affiliates on the High-z team.
Julia Lee, a faculty member who has recently joined the Harvard Astronomy Department, also was recognized in the prize as a member of the Supernova Cosmology Project team.
The $500,000 Gruber Cosmology Prize is awarded in partnership with the International Astronomical Union. According to its sponsor, the Peter & Patricia Gruber Foundation, the Cosmology Prize honors a leading cosmologist, astronomer, astrophysicist or scientific philosopher for theoretical, analytical or conceptual discoveries leading to fundamental advances in the field.
The two teams receiving the 2007 Prize were cited because “the discovery of the accelerated expansion has radically changed our perception of cosmic evolution.” Astronomers now recognize that the universe is dominated by dark energy, and that the eventual fate of the universe is inextricably tied to the presence of dark energy and dark matter.
“I think this discovery represents the end of the beginning for cosmology,” said Adam Riess (Johns Hopkins University and Space Telescope Science Institute), who led the study for which the group is being honored. “The universe’s constituents have been plumbed, though their nature remains a mystery.”
In 1997, the High-z team’s analysis of observations of distant exploding stars first showed evidence that the expansion of the universe is speeding up. That discovery flew in the face of common wisdom that the universe’s expansion should be slowing due to gravity.
The team examined so-called Type Ia supernovae, which act as “standard candles” since their intrinsic brightness is known. By measuring the observed brightness and recession velocity due to cosmic expansion (or redshift), astronomers can calculate the distance to the supernova. Their calculations showed that the farthest supernovae were dimmer than expected, and therefore more distant than expected. As a result, the universe had to be expanding faster than expected.
“When Adam Riess told me what the data were saying, late in 1997, I could not believe it,” said Kirshner. “We double-checked the analysis and got the same answer. That’s when the horrible truth dawned on me: we had a result that was going to turn this field upside down.”
The High-z Supernova Search team announced their discovery of the accelerating universe in February 1998. A detailed paper was submitted to the Astronomical Journal in March 1998 and published in September (Riess et al. 1998, AJ, 116, 1009). It is available online at http://www.journals.uchicago.edu/AJ/journal/issues/v116n3/980111/980111.web.pdf.
In the nine years that followed, study after study has confirmed the findings of the High-z Supernova Search team and the Supernova Cosmology Project. The current standard model for cosmology describes a universe that is 70 percent dark energy, 25 percent dark matter, and only 5 percent normal matter.
“I am still trying to come to grips with our discovery of an accelerating universe,” said Schmidt. “It didn’t make much sense in 1998, and the whole notion of dark energy that seems to make up most of our universe is still very foggy.”
“We don’t know what the dark energy really is, and we don’t know what the dark matter really is,” summarized Kirshner. “We’ve got a lot of work still to do!”
The Cosmology Prize will be officially awarded at a ceremony in Cambridge, UK on Sept. 7, 2007. The $500,000 prize will be shared in four parts: by Brian Schmidt, Saul Perlmutter, and the two teams, which included fifty-one co-authors between the two key papers.
The full list of High-z Supernova Search team members who will share the Cosmology Prize, and their current affiliations, is Brian Schmidt (Australian National University), Peter Challis (Harvard University), Alejandro Clocchiatt (Pontificia Universidad Catolica 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), and John L. Tonry (Institute for Astronomy, Honolulu).
The official announcement of the 2007 Gruber Cosmology Prize, as well as more information about the Gruber Foundation and its programs, can be found on the Web at http://www.gruberprizes.org/.
Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.