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Dark energy, the Milky Way galaxy and giant planets: Sloan Digital Sky Survey continues (Forwarded)



 
 
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Old January 11th 08, 02:47 AM posted to sci.space.news
Andrew Yee[_1_]
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Default Dark energy, the Milky Way galaxy and giant planets: Sloan Digital Sky Survey continues (Forwarded)

Sloan Digital Sky Survey

Contacts:

Daniel Eisenstein, Director of Sloan Digital Sky Survey III
University of Arizona
520-621-5904

David Weinberg, Scientific Spokesperson
Sloan Digital Sky Survey
614-406-6243

James Gunn, SDSS-II Project Scientist
Princeton University
609-258-3801

Gary S. Ruderman, Public Information Officer
Sloan Digital Sky Survey
312-320-4794

January 10, 2008

Dark energy, the Milky Way galaxy and giant planets: Sloan Digital Sky
Survey continues

Building on eight years of extraordinary discoveries by the Sloan Digital
Sky Survey (SDSS and SDSS-II), a new program of four coordinated surveys
will revolutionize the study of the distant universe, the Milky Way galaxy,
and giant planets orbiting other stars. The largest of these surveys will
use a novel and powerful technique to study dark energy, one of the biggest
mysteries in contemporary science.

"The cosmological measurements in SDSS-III could rewrite fundamental
physics, either pinning down the properties of an exotic form of energy that
fills the universe or showing that Einstein's theory of gravity fails at
cosmological distances," explains Daniel Eisenstein of the University of
Arizona and director of the newly formed collaboration.

The SDSS-III program was announced today at the American Astronomical
Society meeting in Austin, Texas. It is described in a poster presentation
entitled SDSS-III: Massive Spectrographic Surveys of the Distant Universe,
the Milky Way Galaxy and Extra-Solar Planetary Systems."

The Alfred P. Sloan Foundation of New York has approved a $7 million grant
in support of SDSS-III, conditional on raising the additional funds from
collaboration members and federal agencies needed to complete the project.

SDSS-III is slated to run from mid-2008 to mid-2014. Its four component
surveys will all operate from the 2.5-meter telescope at Apache Point
Observatory in New Mexico, using optical fibers to capture the light of
hundreds of objects simultaneously. This technique allowed the SDSS and
SDSS-II to create the largest three-dimensional map of the present-day
universe.

The largest of the four surveys, the Baryon Oscillation Spectroscopic Survey
(BOSS), will measure the expansion of the universe with unprecedented
precision. A decade ago, Eisenstein explains, astronomers made the startling
discovery that the expansion of the universe is speeding up. "It's like
tossing a ball in the air, waiting for it to fall, and instead seeing it
accelerate upwards and disappear from sight."

Cosmologists attribute this acceleration to so-called "dark energy," which
pervades otherwise empty space and exerts repulsive gravitational force.
Dark energy could be the cosmological constant proposed by Albert Einstein
in 1917, or it could be a new form of energy whose properties evolve with
time. Distinguishing these possibilities, or determining whether the theory
of gravity itself is at fault, requires measuring the history of cosmic
expansion with very high precision, explains David Schlegel of Lawrence
Berkeley National Laboratory, principal investigator of BOSS.

In 2005, the SDSS achieved one of the first clear detections of "baryon
acoustic oscillations," a feature imprinted on the clustering of galaxies by
sound waves that traveled in the early universe. BOSS will use this feature
as a "yardstick in the sky" to measure cosmic distances, says Schlegel. "Our
measurements should reach one-percent accuracy and extend to distances of
ten billion light years, giving us strong tests of dark energy theories."

While new, more sensitive instruments are being constructed for BOSS,
SDSS-III will carry out a one-year extension of SEGUE, an SDSS-II survey
mapping the outer Milky Way. "The Galaxy's stellar halo is much more complex
than anyone realized a decade ago, and we want to understand what that is
telling us about the formation of the Milky Way," explains Constance Rockosi
of the University of California at Santa Cruz, the principal investigator of
SEGUE-2.

Interstellar dust blocks visible light coming from stars in the inner Milky
Way. Infrared light penetrates this dust, revealing stars even from heavily
obscured regions near the Galactic center. The new APOGEE survey will employ
a unique new instrument that observes infrared light from 300 stars
simultaneously, enabling a survey of 100,000 stars across the entire Galaxy.

"When stars die, the chemical elements forged by nuclear reactions in their
cores are released into space," explains Steven Majewski of the University
of Virginia, principal investigator of APOGEE. "The APOGEE measurements will
provide detailed chemical 'fingerprints' for each target star, which in turn
reveal the properties of the stars that preceded them. It's the ultimate
exercise in forensic archeology."

And what about planets orbiting those stars? Of the 200 or so planetary
systems currently known, most are very different from our own solar system,
notes Jian Ge of the University of Florida. The majority of known planets
are gaseous giants, like Jupiter, but they follow elongated (instead of
circular) trajectories and orbit much closer to their parent stars.

Ge is the principal investigator of MARVELS, which will search more than
10,000 stars for orbiting giant planets, a three-fold increase on the number
searched by all other telescopes to date. "By systematically monitoring such
a large number of stars," says Ge, "MARVELS will address two of the biggest
questions in planetary science: how do giant planets form, and why are so
many in such unusual orbits?"

Jim Gunn of Princeton University, who has led nearly two decades of
construction and operation of the Sloan Digital Sky Survey, is excited about
its new ventures. "It's amazing to see that the SDSS can transform
scientific fields we hadn't even conceived of 20 years ago."

Definitions:

* BOSS -- Baryon Oscillation Spectroscopic Survey
* SEGUE and SEGUE 2 -- Sloan Extension for Galactic Understanding and
Exploration
* APOGEE -- Apache Point Observatory Galactic Evolution Experiment
* MARVELS -- Multi-Object Apache Point Observatory Radial Velocity Exoplanet
Large-area Survey

Authors:

* David H. Weinberg, Ohio State University
* T. Beers, Michigan State University
* M. Blanton, New York University
* D. Eisenstein, University of Arizona
* H. Ford, The Johns Hopkins University
* J. Ge, University of Florida
* B. Gillespie, Apache Point Observatory
* J. Gunn, Princeton University
* M. Klaene, Apache Point Observatory
* G. Knapp, Princeton University
* R. Kron, University of Chicago
* S. Majewski, University of Virginia
* R. Nichol, University of Portsmouth, UK
* R. W. O'Connell, University of Virginia
* M. J. Raddick, The Johns Hopkins University
* C. Rockosi, University of California, Santa Cruz
* N. Roe, Lawrence Berkeley National Laboratory
* R. Schiavon, Gemini Observatory
* D. Schneider, Pennsylvania State University
* D. Schlegel, Lawrence Berkeley National Laboratory
* M. Skrutskie, University of Virginia
* S. Snedden, Apache Point Observatory
* M. Strauss, Princeton University
* X. Wan, University of Florida
* M. White, University of California, Berkeley

[NOTE: Images supporting this release are available at
http://www.astronomy.ohio-state.edu/...3/sdss3pr.html ]
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