The Sloan Digital Sky Surveys have formed important catalogs of parts of the night sky to answer some fundamental questions and lead to new ones. A description of the project is here (pdf) - a bit techncal, but the introduction
The past decade has seen extraordinary progress in our understanding of the Universe, the Milky Way galaxy, and the population of extra-solar planets. A wide range of observations have converged on a consistent cosmological model that incorporates cold dark matter, a baryon-to-dark-matter ratio ∼1:6, flat space, and primordial fluctuations with the statistical properties predicted by infla- tion. This model requires one very surprising ingredient, “dark energy,” which drives accelerating expansion of the Universe. Large-scale imaging and spectroscopic surveys have revealed rich, com- plex structure in the outer Milky Way, residual traces of the Galaxy’s hierarchical formation history. These surveys have discovered more than a dozen new members of the Local Group of galaxies and identified thousands of the most chemically primitive stars in the Milky Way. The population of known extra-solar planets has grown from a handful to over 200. Many of the newly discovered systems are radically different from our own solar system, while others could possibly harbor life like that on Earth.
The Sloan Digital Sky Survey (SDSS), both the original 5-year program and its ongoing 3- year extension (SDSS-II), has made enormous contributions across a wide span of astronomical fields, including contributions to many of the discoveries mentioned above. Along the way it has exemplified a new mode of astronomical discovery, with teams of scientists cooperating in organized, systematic surveys to produce large data sets that are made publicly available and support a rich variety of investigations. The result has been unprecedented productivity: 1500 SDSS-based papers published in refereed journals, more than five dozen PhD theses, and 16 of the top 100 cited papers in the past five years. In a recent analysis of the observatories with the highest impact on astronomy, the SDSS has been ranked at the top for three of the last four years (see §2).
Building on this extraordinary legacy, we propose a six-year program (2008-2014) that will use the SDSS facilities at Apache Point Observatory (APO) to carry out four surveys on three scientific themes: dark energy and cosmological parameters; the structure, dynamics, and chemical evolution of the Milky Way; and the architecture of planetary systems. The wide field of view and efficient, multiplexed spectroscopic capability of the APO 2.5-m telescope make it ideally suited to exploit the new opportunities arising from recent discoveries in these fields. The overall program is divided into dark-time (moonless) and bright-time surveys. The main dark-time survey, which takes five years, is a precision measurement of the cosmic distance scale and the effects of dark energy (BOSS). The first year of dark time will be devoted to a spectroscopic study of the structure and chemical evolution of the Milky Way (SEGUE-2). The bright-time surveys are a high-resolution infrared spectroscopic survey that can penetrate obscuring dust to see deep into the heart of the Milky Way (APOGEE), and a highly multiplexed search for extra-solar planets (MARVELS). These surveys can observe simultaneously with each other and with an extension of SEGUE-2 that concentrates on bright stars. Each of the four surveys will produce the largest and most powerful data set of its kind over the next decade, and the combination of surveys efficiently devotes all of the available observing time to a rich program of first-class science.
The acceleration of the expansion of the Universe poses the most profound question in physical science today. Even the most prosaic explanations of cosmic acceleration demand the existence of a pervasive new component of the Universe with exotic physical properties. More extreme alternatives include extra spatial dimensions or a breakdown of General Relativity on cosmological scales. To distinguish competing hypotheses, we require precise measurements of the cosmic expansion history over a wide span of time. Of the four most widely studied measurement techniques, the “baryon acoustic oscillation” method, pioneered in the SDSS, is especially attractive for its simplicity and its freedom from systematic uncertainties. Sound waves that propagate in the hot plasma of the early
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Recently a gee-whiz view of a 3d flythrough of galaxies was created from the latest data release
The Sloan Digital Sky Survey III (SDSS-III) has released the largest-ever three-dimensional map of massive galaxies and distant black holes, which will help astronomers explain the mysterious dark matter and dark energy that makes up 96 percent of the universe.
Data Release 9 is the latest in a series of data releases stretching back to 2001. This release includes new data from the ongoing SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), which will eventually measure the positions of 1.5 million massive galaxies over the past six billion years of cosmic time, as well as 160,000 quasars — giant black holes actively feeding on stars and gas — from as long ago as 12 billion years in the past.
Carl Sagan would have loved it.