About SDSS

Mapping the Universe

Mapmaking—laying a gridwork for reality—is an activity central to the step-by-step advance of human knowledge. Recently there has been an explosion in the scale and diversity of mapmaking enterprises, in fields as disparate as genetics, oceanography, neuroscience, and surface physics, applying ever-improving computer technology to the task of exploring enormous and complex new territories. This ability to record and digest immense quantities of data in a timely way is changing the face of science. The Sloan Digital Sky Survey (SDSS), the most ambitious astronomical survey project ever undertaken, applies this ability to cosmography, the science of mapping the universe and determining our place in it.

SDSS is systematically mapping a 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 is also measuring the distances 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. SDSS is also recording the distances to 100,000 quasars — the most distant objects known — giving us unprecedented knowledge of the distribution of matter to the edge of the visible universe.

New Discoveries

In 2006, SDSS advanced mankind's understanding of the universe with several new discoveries. The survey found new dwarf companion galaxies to the Milky Way; confirmed Einstein's prediction of cosmic magnification; observed the largest known structures in the universe (measuring more than a billion light years across); and further unraveled our galaxy's active past, filled with galactic mergers. In the coming years, SDSS will continue to expand our horizons with new studies of the structure and origins of the Milky Way Galaxy and the nature of dark energy.

As the first large-area survey to use electronic light detectors, SDSS produces images substantially more sensitive and accurate than earlier surveys, which relied on photographic techniques. The results are available to the scientific community electronically, both as images and as precise catalogs of all objects discovered. SDSS also represents a significant increase in scale. The total quantity of survey information produced (about 15 terabytes, or a trillion bytes) rivals the information content of the Library of Congress.

By systematically and sensitively observing such a large fraction of the sky, SDSS has had a significant impact on astronomical studies. It represents a new reference point, a field guide to the universe at the millenium, which will be used by scientists for decades to come.