The ability to record and digest immense quantities of data in a timely way is changing the face of science. The Sloan Digital Sky Survey, the most ambitious astronomical survey project ever undertaken, will bring this modern practice of comprehensive and quantitative mapping to cosmography, the science of mapping the universe and determining our place in it.  The Sky Survey will systematically map one-quarter of the entire sky, producing a detailed image of it and determining the positions and absolute brightnesses of more than 100 million celestial objects. It will also measure the distance to a million of the nearest galaxies, giving us a three-dimensional picture of the universe through a volume one hundred times larger than that explored to date. The Sky Survey will also record the distances to 100,000 quasars, the most distant objects known, giving us an unprecedented hint at the distribution of matter to the edge of the visible universe.

The 2.5-meter reflecting telescope of the Sloan Digital Sky Survey. The box-like structure protects the separately mounted telescope from being buffeted by the wind.

As the first large-area survey to use electronic light detectors, the image it produces will be substantially more sensitive and accurate than earlier surveys, which relied on photographic techniques. The results of the Sky Survey will be available to the scientific community electronically, both as images and as precise catalogs of all the objects discovered. The Sky Survey also represents a significant increase in scale. The total quantity of information produced, about 15 terabytes (trillion bytes), rivals the data content of the Library of Congress.  By systematically and sensitively observing such a large fraction of the sky, the Sky Survey will have a significant impact on astronomical studies as diverse as the large-scale structure of the universe, the origin and evolution of galaxies, the relation between dark and luminous matter, the structure of our own Milky Way, and the properties and distribution of the dust from which stars like our sun were created. It will represent a new reference point, a field guide to the universe at the millenium, which will be used by scientists for decades to come.

Redshift 5.8 Quasar: The arrow in this image points to the most distant quasar ever observed, with a record-shattering redshift of 5.8. SDSS astronomers identified this faint speck of light as a possible quasar based on its distinctive red color. A spectrum of this object, obtained with the 10-meter Keck telescope in Hawaii, showed that this was indeed a quasar with a most impressive redshift.