UC Berkeley News
Berkeleyan

Berkeleyan

 Saul Perlmutter (Courtesy Lawrence Berkeley National Laboratory)

Berkeley's Perlmutter shares Gruber Cosmology Prize
Prize committee takes care to recognize most of the contributors to the work of both honored teams - many of whom have studied or worked at Berkeley

| 22 August 2007

Researchers at Berkeley and 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, which was announced in July and will be awarded in September, recognizes Saul Perlmutter, a Berkeley physics professor and 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 Gruber Cosmology Prize, awarded (since 2001) in collaboration with the International Astronomical Union, is given in recognition of theoretical, analytical, or conceptual discoveries leading to fundamental advances in the field. 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, postdoctoral researchers, and graduate students from Berkeley.

"The Gruber Cosmology Prize is a great honor for all of us in both teams," says 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 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.

"I am happy to see all of the members of these two teams honored for their hard work," says Riess, 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," adds 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 says he came to 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," says 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 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, a 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. 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," says 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," adds 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 governs 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.