From: Jeanne Miller (JMMiller@lbl.gov)
Date: Thu Sep 26 2002 - 09:21:54 PDT
attached mail follows:
Saul Perlmutter Wins E. O. Lawrence Award in Physics
Contact: Paul Preuss, paul_preuss@lbl.gov
An online version of this release, with illustration, can be
found at
http://www.lbl.gov/Science-Articles/Archive/Phy-Lawrence-Award-Perlmutter.html
BERKELEY, CA -- Saul Perlmutter, a member of Lawrence
Berkeley National Laboratory's Physics Division and leader
of the international Supernova Cosmology Project based here,
has won the Department of Energy's 2002 E. O. Lawrence Award
in the physics category. Perlmutter is Berkeley Lab's 25th
recipient of the prestigious award, which includes a gold
medal and $25,000.
Perlmutter will be cited at the awards ceremony in
Washington D.C. on October 28 "for his leading contributions
to an unexpected discovery of extraordinary importance: the
determination, through the careful study of distant
supernovae, that the expansion of the universe is speeding
up rather than slowing down." The announcement of the
"accelerating universe" in 1998 was named scientific
"breakthrough of the year" by the journal Science.
"We are all enriched by the contributions these researchers
have made, ranging from understanding the genetic code to
measuring the expansion of the universe itself," said
Secretary of Energy Spencer Abraham.
Said Berkeley Lab Director Charles V. Shank, "We are proud
that the techniques for measuring cosmic expansion were
developed and proven at Berkeley Lab under Saul's leadership
of the Supernova Cosmology Project. His Lawrence Award
recognizes the kind of imaginative basic research done here
to address the most fundamental questions about nature,
yielding knowledge whose benefits we may only begin to
imagine."
The Lawrence Awards, established by Dwight D. Eisenhower in
1959 as a memorial to Ernest Lawrence, are chosen by
independent panels from thousands of nominations by
scientists and research organizations. The awards recognize
achievements in atomic research, broadly defined, and are
intended to encourage the careers of scientists who show
exceptional promise.
In addition to Perlmutter's award in physics, this year's
winners are, in chemistry, Keith O. Hodgson of the Stanford
Linear Accelerator Center; in environmental science and
technology, Benjamin D. Santer of Lawrence Livermore
National Laboratory; in life sciences, Claire M. Fraser of
the Institute for Genomic Research; in materials research,
C. Jeffrey Brinker of Sandia National Laboratory and the
University of New Mexico; in national security, Bruce T.
Goodwin of Lawrence Livermore National Laboratory; and in
nuclear technology, Paul J. Turinsky of North Carolina State
University.
The fundamental questions:
"What is true about the world no matter where, no matter
when?" is the kind of question that has fascinated Saul
Perlmutter since childhood. After graduating magna cum laude
in physics from Harvard in 1981, he headed for graduate work
at the University of California at Berkeley, where he soon
realized that to pursue such fundamental questions in
high-energy physics would require vast machines "and involve
hundreds of people. So I thought it would be fun to try
astrophysics."
Many of Perlmutter's subsequent accomplishments, notably his
leading role in the discovery of the universe's accelerating
expansion, owe much to the practical methods he and his
colleagues devised for using supernovae as "standard
candles" to measure the cosmic expansion rate.
Astronomical standard candles are objects whose calculable
brightness reveals their distance from our solar system,
just as the apparent brightness of a candle depends on its
distance across a room. Supernovae are among the brightest
objects in the universe, visible at much greater distances
than other standard candles like Cepheid variable stars.
Although the idea had been circulating within the
astronomical community for years, Perlmutter says, "In the
early days, people thought measuring expansion with
supernovae would be hard." Different kinds of supernovae
explode in different ways, and it wasn't apparent that any
were really "standard."
Moreover, in a universe filled with some hundred billion
galaxies of a hundred billion stars each, finding random
exploding stars with a telescope was a chancy business; in
the 1980s, one search for the extremely distant supernovae
required to measure changes in the universe's expansion rate
found only a single supernova after two and a half years of
looking -- and that one was already faded past its peak
brightness.
The group in which Perlmutter did his graduate work, headed
by Berkeley Lab and UCB physicist Richard Muller, was
constructing a robotic telescope to look for relatively
nearby Type II "core collapse" supernovae, whose brightness,
it was thought, could be calculated from the velocity of
their expanding shells. Although the robotic search was
successful, finding some 20 supernovae, distance measurement
with Type IIs was "a tough technique, still not perfected,"
Perlmutter remarks.
"In the meantime Carl Pennypacker and I, the two postdocs in
the group, got interested in looking at Type Ia supernovae
at much greater distances," says Perlmutter, "and we began
what was later called the Supernova Cosmology Project." Type
Ia supernovae were not only brighter than Type IIs but, if
carefully distinguished from superficially comparable types,
had proved impressively similar in brightness.
Supernova cosmology -- the early days:
To find enough Type Ia's for meaningful data about
expansion, Perlmutter and Pennypacker wanted to use a
wide-area telescope to scan thousands of galaxies at once.
But competition for telescope time among astronomers was
fierce. It was a time when sensitive CCDs (charge-coupled
devices) were fast replacing photographic plates in
astronomy, and they found an Australian observatory willing
to trade observing time for a custom-made CCD camera with a
novel wide-area design.
"In exchange for building the camera we got 12 nights,
spaced over many months," Perlmutter says. "The weather was
good for just two and a half of those nights."
During those two and a half nights they found what
Perlmutter calls a "promising" Type Ia supernova, "but we
couldn't prove it." It's what he calls "a major
chicken-and-egg problem: you couldn't prove you'd found a
supernova unless you could get access to a big telescope,
but you couldn't get access to a big telescope unless you
could prove you'd found a supernova."
In 1992, working at the Isaac Newton Telescope in La Palma,
the Canary Islands, they finally found their first
convincing Type Ia supernova. By 1994 the Supernova
Cosmology Project had managed to scrounge enough telescope
time to prove it could produce large numbers of "supernovae
on demand."
"In retrospect it seems obvious, but we realized that the
whole process could be systematized. The key was to clump
the observations," Perlmutter explains. "By searching the
same group of galaxies three weeks apart, we could find
supernovae candidates that had appeared in the meantime. We
could guarantee four to eight supernovae each time, and all
of them would be on the way up" ?? growing brighter instead
of already fading.
"The first time we tried this scheduling scheme, at the Kitt
Peak and La Palma observatories in late 1993 and early 1994,
we found five supernovae," Perlmutter says. Their success
inspired others who had initially been skeptical. "Since
then everybody has done it. It became a race to build a
statistically significant sample."
Facing up to the cosmos:
Years of refining theory and observational techniques and
painstaking data analysis followed. In 1998 the Supernova
Cosmology Project and the competing High-Z Supernova Search
Team came to a conclusion that both had initially resisted:
the expansion of the universe is not slowing, as everyone
had assumed. On the contrary.
"The chain of analysis was so long that at first we were
reluctant to believe our result," Perlmutter explains. "But
the more we analyzed it, the more it wouldn't go away."
The discovery that the universe is expanding at an
accelerating pace, soon bolstered by independent
measurements of other cosmological parameters, instantly
revolutionized cosmology. Apparently some mysterious "dark
energy" drives cosmic acceleration and constitutes
two-thirds of the density of the universe; the nature of
dark energy is one of the most significant questions facing
high-energy physics in the 21st century.
"This discovery was very much a team effort," Perlmutter
stresses, citing the efforts of the Supernova Cosmology
Project's individual members in theoretical studies of
supernova dynamics, the detection of supernovae near and
far, data analysis and interpretation, and other research
components.
Moreover, Perlmutter says, the sustained effort that led to
the breakthrough was possible because of Berkeley Lab's
unique status as a national laboratory. "It was the freedom
to look ahead that the Lab offered. No one knew if the
effort would work, and it was ten years before there was a
result. Where else could you find the support to do that?"
The Berkeley Lab is a U.S. Department of Energy national
laboratory located in Berkeley, California. It conducts
unclassified scientific research and is managed by the
University of California. Visit our website at
http://www.lbl.gov
Additional information:
The Department of Energy announcement of the Lawrence Awards
can be found at
http://www.energy.gov/HQPress/releases02/seppr/pr02199.htm
More about the Supernova Cosmology Project can be found at
http://panisse.lbl.gov/
More about the SuperNova/Acceleration Probe (SNAP satellite)
can be found at http://snap.lbl.gov/
More about Saul Perlmutter can be found at
http://www.lbl.gov/wonder/perlmutter.html
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