Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Astronomers Begin New Search for Dark Energy

02.10.2009
Astronomers from the University of Arizona and 41 other institutions are beginning the most ambitious project yet to map the three-dimensional structure of the universe in a quest to understand dark energy.

"Making a three-dimensional map is essential to understanding why the universe is expanding at an ever-accelerating rate," said UA astronomy professor Daniel Eisenstein, director of the Sloan Digital Sky Survey III, known an SDSS-III, a collaboration of 350 scientists.

The new SDSS-III mapping project, called the Baryon Oscillation Spectroscopic Survey, or BOSS, collected its first astronomical data -- a milestone called achieving "first light" -- on a thousand galaxies and quasars on Sept. 14 - 15.

The BOSS team uses new, extremely sensitive optical-infrared spectrographs on the Sloan Foundation 2.5-meter telescope at Apache Point Observatory in New Mexico.

Their goal is to collect spectra for 1.4 million galaxies and 160,000 quasars by 2014.

Measuring the spectra, or colors, of galaxies and quasars allows astronomers to determine how far away and how far back in time these celestial objects are.

"The data from BOSS will be the best ever obtained on the large-scale structure of the universe," said BOSS principal investigator David Schlegel of the U.S. Department of Energy's Lawrence Berkeley National Laboratory.

In the early universe, cosmic matter -- the protons and neutrons, or "baryons" -- interacted with the light from the Big Bang to create pressure oscillations much like sound waves. Just as sound waves compress air molecules in our atmosphere, these "baryon acoustic oscillations" created density variations as they traveled through the early universe.

When the universe was around 400,000 years old, conditions were finally cool enough to halt the propagation of the sound waves, and this left a "frozen" sound wave signature, said UA astronomy professor Xiaohui Fan.

Fan is UA's representative to the SDSS-III collaboration council.

"We can see these frozen waves in the distribution of galaxies today,"
Eisenstein said. "The signature is that pairs of galaxies are somewhat more likely to be separated by 500 million light years, rather than 400 million or 600 million light years."

The sound wave signature today is expected to be about 500 million light years long because the universe has greatly expanded since those early times, Fan said.

"By measuring the length of the baryon oscillations, we can determine how dark energy has affected the expansion history of the universe,"

Eisenstein said. "That, in turn, helps us figure out what dark energy could be."

Astronomers study baryon oscillations as an exciting new method for measuring "dark energy," the name they give to the mysterious physical mechanism that is causing the universe to expand at an accelerating rate.

Astronomers have known since the 1920s that the universe is expanding, but they were stunned when they discovered in 1998 that the universe is expanding at an accelerating rate.

"We're trying to understand why that is. It's a very odd thing,"
Eisenstein said. "Gravity pulls things together, so you'd expect gravity would be pulling the universe back together so that it would expand at a decelerating rate.

"But something is causing the universe to expand at an accelerating rate. Either we misunderstand how gravity works on the largest scales, or there's some extra thing in the universe that actually causes gravity to repel structure," Eisenstein said.

The BOSS spectrographs have more than 2,000 large metal plates that are placed at the focal plane of the telescope. These plates are drilled with the precise locations of nearly two million objects across the northern sky. Optical fibers plugged into a thousand tiny holes in each of the "plug plates" carry the light from each observed galaxy or quasar to BOSS's new spectrographs.

The SDSS-III team plans to release its first data to the public in December 2010.

About SDSS-III and BOSS

BOSS is the largest of four surveys in SDSS-III, which includes 350 scientists from 42 institutions. The BOSS design and implementation has been led from the U.S. Department of Energy's Lawrence Berkeley National Laboratory. The optical systems were designed and built at Johns Hopkins University, with new CCD cameras designed and built at Princeton University and the University of California at Santa Cruz/Lick Observatory. The University of Washington contributed new optical fiber systems, and Ohio State University designed and built an upgraded BOSS data-acquisition system. The "fully depleted" 16-megapixel CCDs for the red cameras evolved from Berkeley Lab research and were fabricated in Berkeley Lab's MicroSystems Laboratory.

Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the participating institutions, the National Science Foundation, and the U.S. Department of Energy.

SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration, including the University of Arizona, the Brazilian Participation Group, University of Cambridge, University of Florida, the French Participation Group, the German Participation Group,the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, the U.S. Department of Energy's Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, New Mexico State University, New York University, the Ohio State University, University of Portsmouth, Princeton University, University of Tokyo, the University of Utah, Vanderbilt University, University of Virginia, University of Washington and Yale University.

Lori Stiles | University of Arizona
Further information:
http://research.icg.port.ac.uk/node/940

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Northern oceans pumped CO2 into the atmosphere

27.03.2017 | Earth Sciences

Fingerprint' technique spots frog populations at risk from pollution

27.03.2017 | Life Sciences

Big data approach to predict protein structure

27.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>