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| This is a still image from a video fly-through of the SDSS-III galaxies mapped in Data Release 9 [Credit: Miguel A. Aragón (Johns Hopkins University), Mark SubbaRao (Adler Planetarium), Alex Szalay (Johns Hopkins University), Yushu Yao (Lawrence Berkeley National Laboratory, NERSC), and the SDSS-III Collaboration] |
This is an animated flight through the universe as seen by SDSS. There are close to 400,000 galaxies in the animation, which places zoomed-in images of nearby galaxies at the positions of more distant galaxies mapped by SDSS [Credit: Miguel A. Aragón (Johns Hopkins University), Mark SubbaRao (Adler Planetarium), Alex Szalay (Johns Hopkins University), Yushu Yao (Lawrence Berkeley National Laboratory, NERSC), and the SDSS-III Collaboration]
The map is the centerpiece of Data Release 9 (DR9), which publicly releases the data from the first two years of a six-year survey project. The release includes images of 200 million galaxies and spectra of 1.35 million galaxies. (Spectra take more time to collect than photographs, but provide the crucial third dimension by letting astronomers measure galaxy distances.)
"Our goal is to create a catalog that will be used long after we are done," said Michael Blanton of New York University, who led the team that prepared Data Release 9.
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| BOSS is capturing accurate spectra for millions of astronomical objects by using 2,000 plug plates that are placed at the Sloan Foundation Telescope’s focal plane. Each of the 1,000 holes drilled in a single plug plate captures the light from a specific galaxy, quasar, or other target, and conveys its light to a sensitive spectrograph through an optical fiber. The plates are marked to indicate which holes belong to which bundles of the thousand optical fibers that carry the object’s light [Credit: Lawrence Berkeley National Laboratory and Sloan Digital Sky Survey III] |
BOSS is targeting these big, bright galaxies because they live in the same places as other galaxies and they're easy to spot. Mapping these big galaxies thus provides an effective way to make a map of the rest of the galaxies in the universe.
With such a map, scientists can retrace the history of the universe over the last six billion years. With that history, they can get better estimates for how much of the universe is made up of "dark matter" - matter that we can't directly see because it doesn't emit or absorb light - and "dark energy," the even more mysterious force that drives the accelerating expansion of the universe.
"Dark matter and dark energy are two of the greatest mysteries of our time," said David Schlegel of Lawrence Berkeley National Laboratory, the principal investigator of BOSS. "We hope that our new map of the universe can help someone solve the mystery."
Source: Harvard-Smithsonian Center for Astrophysics [August 08, 2012]