Peter Garnavich, professor of physics at the University of Notre Dame, was a member of the High-Z Supernova Search Team whose leader, Brian Schmidt, shared in the Nobel Prize in physics announced Tuesday (Oct. 4). Garnavich wrote the team's first paper that included supernovae data from the Hubble telescope.
Team member Adam Riess, who wrote the second paper, shared in the Nobel Prize, along with Saul Perlmutter, leader of the rival Supernova Cosmology Project. The researchers demonstrated in the late 1990s that the universe is accelerating, leading to the now-standard understanding of dark energy in the universe.
The High-Z Supernova Search Team organized in 1994 with about 20 members and elected Schmidt as its leader, Garnavich said. The group was looking for very distant supernovae. "We were trying to measure the density of matter which we thought was the only thing in the universe," he said, explaining that researchers at the time were studying whether the universe would continue to expand or whether it would slow and eventually collapse. "My paper didn't have enough supernovae to detect acceleration, but did show the universe would not ever recollapse."
By the time Riess wrote the second paper, in 1998, the group had gathered sufficient data, including more supernovae data from the Hubble, to show that the universe's expansion is accelerating. "This is a big surprise," Garnavich said. "It requires something that Einstein had postulated, the cosmological constant, but then discarded after it was discovered that the universe is expanding. Now we call it dark energy because we don't know what it is." The group went on to study what dark energy might be, and Garnavich led a paper that constrained the variety of possible models that might produce the acceleration. Since then, researchers have cataloged hundreds of supernovae with ground-based telescopes and hope to collect significantly more data with space-based equipment to pursue understanding of dark energy.
The awarding of a Nobel Prize only 13 years after the discovery indicates the significance of the work, Garnavach said. "It was one of biggest discoveries in last 50 years," he said.