A project to investigate the large-scale structure of the Universe by mapping the three-dimensional distribution of galaxies and quasars over a quarter of the sky, mostly around the north galactic pole but with three strips near the south galactic pole. The survey started in 1998 and used a wide-field 2.5-m telescope at Apache Point Observatory, New Mexico. The first phase of observations, SDSS-I, was completed in 2005. It was followed by SDSS-II, in three parts: the Sloan Legacy Survey, to fill remaining gaps in the main survey; SEGUE (Sloan Extension for Galactic Understanding and Exploration), to map the structure and stellar makeup of our own Galaxy from the spectra of 240 000 stars; and the Sloan Supernova Survey, searching for distant Type Ia supernovae to measure changes in the rate of expansion of the Universe. SDSS-II was completed in 2008, bringing the total observations to more than 930 000 galaxies and over 120 000 quasars. SDSS-III began at Apache Point Observatory in 2008 and consists of four surveys: the Baryon Oscillation Spectroscopic Survey (BOSS) which maps the walls and voids in the distribution of galaxies resulting from density fluctuations in the early Universe; SEGUE-2, continuing the original SEGUE study with the spectra of an additional 214 000 stars; the Apache Point Observatory Galactic Evolution Experiment (APOGEE), a spectroscopic survey of 100 000 red giant stars at infrared wavelengths; and the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS), which monitors the radial velocities of 11 000 bright stars for signs of orbiting planets. SDSS-III will continue until 2014.
http://www.sdss.org/ Official project website with many images.
Subjects: Astronomy and Astrophysics.