Interactions News Wire #47-07
5 September 2007 http://www.interactions.org
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Source: Berkeley Lab
Content: Press Release
Date Issued: 5 September 2007
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JOINT DARK ENERGY MISSION A TOP PRIORITY FOR NASA, SAYS NRC
Contact: Paul Preuss, (510) 486-6249, paul_preuss@lbl.gov
[An html version of this release is at
http://www.lbl.gov/Science-Articles/Archive/Phys-JDEM.html]
BERKELEY, CA -- The National Research Council's Beyond Einstein Program
Assessment Committee has recommended that the Joint Dark Energy Mission
(JDEM), jointly supported by the National Aeronautics and Space
Administration and the Department of Energy, be the first of NASA's Beyond
Einstein cosmology missions to be developed and launched.
One of the three competing projects in the JDEM program is Lawrence
Berkeley National Laboratory's SuperNova/Acceleration Probe, or SNAP, a
versatile space-borne observatory with a powerful two-meter-class
telescope and a half-billion pixel imager, designed to study dark energy
by recording the distance and redshift of some 2,000 Type Ia supernovae a
year and mapping the sky with unprecedented resolution. Dark energy is the
name given to the mysterious entity which is causing the universe to
expand ever more rapidly. It accounts for nearly three-quarters of all the
energy in the universe.
The recommendations of NRC's Beyond Einstein Program Assessment Committee
(BEPAC), posted on the internet Sept. 5, follow nearly a year of intensive
study of the five proposed missions in the Beyond Einstein program. Due to
budget constraints and technological readiness only one such mission can
be started at this time, so NASA and DOE requested in August, 2006 that
the NRC, while assessing the program as a whole, recommend which mission
should be developed and launched first.
"NASA and DOE have moved forward together since joining forces on the
Joint Dark Energy Mission four years ago, including their support for
Berkeley Lab's approach to the mission, SNAP," says Steven Chu, Director
of the Department of Energy's Lawrence Berkeley National Laboratory. "By
recommending that JDEM be the first Beyond Einstein mission to be
launched, the National Research Council has assured that the two agencies
will be partners in investigating one of the most pressing scientific
questions of the 21st century. We look forward to the agencies' moving
forward upon receiving the NRC Committee Report."
"It's wonderful to know that NASA will be moving forward with this
exciting project as a result of the committee's recommendation that JDEM
be the first mission to fly," says Saul Perlmutter, a member of Berkeley
Lab's Physics Division and Professor of Physics at the University of
California at Berkeley. "Each of the highly ranked Beyond Einstein
projects will contribute greatly to our understanding of the universe, yet
few questions are more fundamental or pressing than the mysterious nature
of dark energy, which accounts for some three-quarters of the density of
our universe -- but about which we know almost nothing."
"It is not surprising that the BEPAC reaffirmed the importance of the
exciting science that connects quarks with the Cosmos -- the stunning
scientific opportunities, from understanding how the Universe began to
unraveling the mystery of the dark energy to probing black holes, speak
for themselves," says Michael Turner, Professor of Physics and of
Astronomy and Astrophysics at the University of Chicago, who led an NRC
Quarks-to-the-Cosmos study which stimulated the Beyond Einstein program.
However, says Turner, "Today's real milestone is the selection of the
Joint Dark Energy Mission as the first of multiple missions in NASA's
Beyond Einstein program.... JDEM will harness the powerful combination of
two science agencies, DOE and NASA, and the scientists they support, to
shed light on the most abundant and most mysterious stuff in the Universe.
JDEM will set a high mark for the Beyond Einstein missions that follow."
The JDEM Mission to Explore Dark Energy
Three concepts for a JDEM mission have been proposed: the
SuperNova/Acceleration Probe (SNAP), the Dark Energy Space Telescope
(DESTINY), and the Advanced Dark Energy Physics Telescope (ADEPT).
SNAP is being developed by an international collaboration led by principal
investigator Perlmutter and by co-principal investigator and project
director Michael Levi, of Lawrence Berkeley National Laboratory's Physics
Division and UC Berkeley's Space Sciences Laboratory. In addition to
Berkeley Lab, partner institutions include the Space Sciences Laboratory;
the French Space Agency, the Centre National D'Etudes Spatiales; and a
number of U.S. and Canadian universities. DESTINY is led by Tod Lauer of
the National Optical Astronomy Observatory, and ADEPT is led by Charles
Bennett of Johns Hopkins University.
Dark energy, which accounts for about three-quarters of the energy density
of the universe, was unknown before 1998. Early that year two
international teams, the Supernova Cosmology Project based at Lawrence
Berkeley National Laboratory and led by Perlmutter, and the High-Z
Supernova Search Team led by Brian Schmidt of the Australian National
University, independently announced their discovery that the expansion of
the universe is not slowing from the contracting force of gravity but is
in fact growing more and more rapidly. The cause of accelerating expansion
was soon named dark energy.
Perlmutter and Schmidt and the members of their teams share the 2007
Gruber Cosmology Prize for their discovery. Perlmutter, Adam Riess of
Johns Hopkins University, and Schmidt shared the 2006 Shaw Prize in
Astronomy for this discovery. Perlmutter also received the 2006
International Antonio Feltrinelli Prize in the Physical and Mathematical
Sciences, awarded once every five years, for his work leading to the
discovery of dark energy.
"Evidence for dark energy came almost ten years ago," Michael Turner
remarks, "and the mystery of this weird stuff with repulsive gravity which
controls the expansion of the Universe and its destiny has captured the
attention of physicists, astronomers and the public alike." Scientists
still cannot say whether dark energy has a constant value or is changing
over time -- or even whether dark energy is an illusion, with the
accelerating expansion of the universe a consequence of a failure of
general relativity.
SNAP, the SuperNova/Acceleration Probe
It was in 1999, soon after the discovery of dark energy, that members of
the Supernova Cosmology Project joined with their colleagues to devise a
space-based experiment, SNAP, to reveal its nature. Intensive research and
development efforts for SNAP have been vigorously supported by DOE's
Office of Science since it was proposed, and by NASA since 2003, when it
joined with DOE to pursue the Joint Dark Energy Mission.
In May, 2006, NASA, DOE, and NSF's Dark Energy Task Force reported that
different techniques for measuring dark energy in combination "have
substantially more statistical power, much more ability to discriminate
among dark energy models, and more robustness to systematic errors than
any single technique."
"SNAP will investigate dark energy using two independent and powerful
techniques," says Perlmutter, SNAP's principal investigator. "The best
proven and most powerful current technique is to determine changes in the
universe's expansion rate by comparing the redshift and distance of Type
Ia supernovae, of which SNAP will find some 2,000 a year. But we are also
targeting the most promising complementary technique, called 'weak
gravitational lensing.'"
Levi, SNAP's co-principal investigator, explains that "Weak gravitational
lensing has been part of the SNAP concept since its beginning in 1999.
SNAP will make a high-resolution map of the sky covering an area 2,000,000
times larger than the Hubble Deep Field. This map will be sensitive to the
minute distortions of distant galaxy shapes when their light passes
through uneven distributions of matter -- a phenomenon called 'weak
lensing.' Weak lensing promises a powerful way to measure the distribution
of dark matter and to probe dark energy's effect on the growth structure
of the universe. The huge survey map will also provide astronomers with an
unparalleled wealth of high-resolution images never before seen."
NASA incorporated JDEM into the Beyond Einstein program when it was
formulated by the agency's Astronomy and Physics Division in 2004. The
program eventually focused on five such missions: to detect gravitational
waves, provide a more powerful x-ray telescope, investigate models of
cosmic inflation, find black holes, and study the nature of dark energy.
Growing interest in dark energy, which in 2006 was called "among the very
most compelling of all outstanding problems in physical science" by the
Dark Energy Task Force that had been commissioned by NASA, DOE, and the
National Science Foundation, prompted consideration of the relative
urgency of the five Beyond Einstein missions, leading to NASA and DOE's
request in August, 2006, that the National Research Council produce a
report by September, 2007 assessing the five missions and recommending
which should be developed and launched first.
ADEPT and DESTINY, like SNAP, also use more than one measuring technique,
and partly for this reason NASA chose these three proposals for concept
development in 2006. Now that the NRC Beyond Einstein Program Assessment
Committee has recommended that JDEM be the first Beyond Einstein mission
launched, NASA and DOE must jointly choose among the JDEM proposals.
Says Perlmutter, "The Committee's recommendation that JDEM be the first
Beyond Einstein mission to be developed and launched is gratifying to the
many collaborators of SNAP. The whole SNAP team worked for thousands of
hours to answer the Committee's almost 100 questions about the mission,
generating hundreds of pages of written responses and documentation."
In addition to the two lead institutions, the UC Berkeley Space Sciences
Laboratory and Lawrence Berkeley National Laboratory, NASA's Goddard Space
Flight Center, the Jet Propulsion Laboratory, the Fermi National
Accelerator Laboratory, and the Stanford Linear Accelerator Laboratory are
collaborating in development of the SNAP concept, joined by industrial
partners Ball Aerospace & Technologies and the Lockheed Martin Space
Systems Company. Academic institutions who are participating in this work
on SNAP include the American Astronomical Society; the California
Institute of Technology; France's Centre de Physique des Particules de
Marseille (CPPM), Laboratoire d'Astrophysique de Marseille (LAM), and
University of Paris VI (LPNHE), which are funded by the Institut National
de Physique Nucleaire et de Physique des Particules (IN2P3) and Institut
National des Science de l'Univers (INSU) of the Centre National de la
Recherche Scientifique (CNRS), and by the Centre National D'Etudes
Spatiales (CNES); Indiana University; the University of Maryland; the
Rochester Institute of Technology; Sonoma State University; the Space
Telescope Science Institute; Stockholm University; the University of
British Columbia; the University of Chicago; the University of Maryland;
the University of Michigan-Ann Arbor; the University of Pennsylvania; the
University of Victoria; and Yale University.
For more about SNAP, including high-resolution images, visit the SNAP
website at http://snap.lbl.gov/.
For more about JDEM, visit NASA's Beyond Einstein website at
http://universe.nasa.gov/program/probes/jdem.html.
Read the National Research Council's Beyond Einstein Program Assessment
Committee report, NASA's Beyond Einstein Program:
An Architecture for Implementation, at the National Academies Press
website, http://books.nap.edu/catalog.php?record_id=12006.
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.
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