Researchers at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory (LBNL) have been awarded the 2007 Gruber Cosmology Prize for their role in the seminal discovery that the expansion of the universe is accelerating.
This year's prize recognizes Saul Perlmutter, a UC Berkeley physics professor and an LBNL astrophysicist; Brian Schmidt, an astronomer at Australian National University; and the respective international teams they led - the Supernova Cosmology Project and the High-z Supernova Search Team.
The $500,000 award will be shared by Perlmutter, Schmidt and the other members of the two supernova teams, which included 51 researchers from around the world. Both teams included faculty, post-doctoral researchers and graduate students from UC Berkeley.
"The Gruber Cosmology Prize is a great honor for all of us in both teams," said Perlmutter. "It's rare that a scientific prize is able to include a very large number of those in the community whose work became the underpinnings of the discovery being celebrated. Yet with the exception of a few notable contributors, that's the case here - and that's terrific."
Each team presented its findings in two key papers, which were specifically noted by the Gruber award committee and whose co-authors comprise the list of awardees. Adam Riess was a Miller Postdoctoral Research Fellow at UC Berkeley working with astronomy professor Alex Filippenko on the High-z team when he led the study for which the group is being honored. Riess produced the bulk of the analysis for the team and was lead author of its publication.
UC Berkeley Chancellor Robert Birgeneau said, "Perlmutter, Schmidt, Riess, Filippenko and their many colleagues are responsible for one of the most striking and counter-intuitive scientific discoveries in recent history. It seems likely that scientists will be working for decades to unravel the fundamental physics underlying dark energy. I am very proud of the role that Berkeley and LNBL scientists played in this discovery and, of course, grateful to the Gruber Prize committee for having the perspicacity to recognize so many of the contributors."
"I am happy to see all of the members of these two teams honored for their hard work," said Riess, who is now a professor of astronomy and physics at Johns Hopkins University and an astrophysicist at the Space Telescope Science Institute.
"The Gruber Foundation should be commended for honoring the teams as well as their leaders," added Filippenko. "Many people worked very hard on the research that led to this fantastic discovery, and it's wonderful to see their accomplishments recognized in this way."
Riess said he came to UC Berkeley 11 years ago because of Filippenko's world-renowned expertise in identifying and analyzing supernovae. Critical to the observations was Filippenko's ability to measure the nature of the supernova explosions in distant galaxies whose apparent brightness was used to derive accurate distances. The explosions occurred billions of light-years away, providing researchers with a glimpse into the past.
"When Adam Riess first showed me the evidence for his conclusion that the expansion of the universe is accelerating, I was truly shocked," said Filippenko, who was a member of both the Supernova Cosmology and High-z teams. "I thought there must be some kind of mistake in the data analysis or interpretation."
Supernova Cosmology Project co-founder Carl Pennypacker, now with UC Berkeley's Space Sciences Laboratory and a guest in LBNL's Physics Division, recalls that in the beginning, "the most striking part of the project was the huge skepticism" - not only about proposed techniques but even about the underlying science. "Nobody believed we could do it, and it was an enormous challenge to get things done."
Having spent eight years on supernova searches and measurements, Gerson Goldhaber, UC Berkeley physics professor, astrophysicist at the Physics Division of LBNL and a member of the Supernova Cosmology Project, recalls the moment he realized what the findings from the team meant. "We had set out to measure the deceleration of the universe, and we found it was accelerating," he said. "This was one of the eureka moments I have been privileged to observe."
The results were unexpected, as most cosmologists at the time believed that the expansion of the universe was slowing down. The big question was whether the universe would expand forever while gradually slowing down, or eventually halt its expansion and start contracting in on itself due to gravity.
The discovery of an accelerating universe turned those beliefs around, giving birth to the theory of dark energy - a mysterious, gravitationally repulsive effect that is causing the expansion to speed up with time.
It is now believed that up to three-quarters of the cosmos consists of dark energy. "I think these discoveries represent the end of the beginning for cosmology," said Riess. "The universe's constituents have been plumbed, though their nature remains a mystery."
"The discovery of the accelerating expansion of the universe, driven by some kind of unknown 'dark energy,' was tremendously exciting," said Filippenko. "In my wildest dreams, I didn't imagine that I would be involved in such an amazing breakthrough."
It is now widely thought that a deep understanding of dark energy will require a unification of the two great pillars of modern physics: quantum mechanics, which govern the physics of small, atomic and subatomic particles, and Albert Einstein's general theory of relativity, describing the physics of large, massive bodies.
The same work being recognized by the Gruber Foundation has been honored previously, most recently by a $1 million Shaw Prize in 2006 that was shared by Perlmutter, Riess and Schmidt.
The Gruber Cosmology Prize is given in recognition of theoretical, analytical or conceptual discoveries leading to fundamental advances in the field. Since 2001, the prize has been awarded in collaboration with the International Astronomical Union.