Monday, March 24, 2008

Dark Energy: Beyond Einstein Missions


Charles L. Bennett

"ADEPT will measure these supernovae, but its real advance lies in a new, more powerful technique. Patterns in temperature of the very young universe provide a 'standard ruler' that is imprinted on the pattern of galaxies across the sky. ADEPT aims to map these through space and time," according to Bennett

ADEPT promises to provide the galaxy positions needed to follow the historical development of the universe, so that astronomers can determine the role played by the dark energy. Bennett says that the ADEPT mission will help answer many questions about the role played by dark energy in both fundamental physics and cosmology. Jonathan Bagger, chair of the Johns Hopkins physics and astronomy department, agreed. "Twenty-first century physics is at a crossroads," he said. "Our fundamental theories of gravity and quantum mechanics are in conflict. Dark energy might point the way out."
See: for Concept Development-Lisa De Nike">NASA Selects Hopkins-led "ADEPT" Space Mission
for Concept Development


Artist's rendition of the Destiny spacecraft-Image Credit: NASA/GSFC

Known as Destiny, the Dark Energy Space Telescope, the small spacecraft would detect and observe more than 3,000 supernovae over its two-year primary mission to measure the expansion history of the Universe, followed by a year-long survey of 1,000 square-degrees of the sky at near-infrared wavelengths to measure how the large-scale distribution of matter in the Universe has evolved since the Big Bang. Used together, the data from these two surveys will have 10 times the sensitivity of current ground-based projects to explore the properties of Dark Energy, and will provide data critical to understanding the origin of Dark Energy, which is poorly explained by existing physical theories.

“Destiny’s strength is that it is a simple, low-cost mission designed to attack the puzzling problem of Dark Energy directly with high statistical precision,” said Tod R. Lauer, the Principal Investigator for Destiny and an astronomer at NOAO. “We build upon grism technology used in the Hubble Space Telescope’s Advanced Camera for Surveys to help us provide spectra of the supernovae as well as images. Spectra are critical to diagnosing the properties of the supernova, but are very difficult to obtain with more traditional cameras. Destiny’s grism camera, however, will take simultaneous spectra of all objects in its field. This is a major advantage of our approach, which greatly increases the ability to detect and characterize these distant stellar explosions.”
See:NASA Funds Development of Destiny: The Dark Energy Space Telescope


NASA will support the SNAP mission concept for probing dark energy by observing distant Type Ia supernova and studying weak gravitational lensing.

SNAP, the SuperNova/Acceleration Probe, is an experiment designed to learn the nature of dark energy by precisely measuring the expansion history of the universe. At present scientists cannot say whether dark energy has a constant value or has changed over time — or even whether dark energy is an illusion, with accelerating expansion being due to a gravitational anomaly instead.

"SNAP will investigate dark energy using two independent and powerful techniques," says Saul Perlmutter of Berkeley Lab's Physics Division, a professor of physics at the University of California at Berkeley who is principal investigator of SNAP and leader of the international Supernova Cosmology Project based at Berkeley Lab. "The best proven and most powerful current technique is to determine changes in the expansion rate by comparing the redshift and distance of Type Ia supernovae, but we are also targeting the most promising complementary technique, called 'weak gravitational lensing.'"
See: SNAP Wins NASA Support for Joint Dark Energy Mission

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