Sloan Digital Sky Survey

Sloan Digital Sky Survey (SDSS) is a large-scale astronomical survey conducted by the Sloan Foundation. It uses a dedicated 2.5-meter telescope at Apache Point Observatory in New Mexico to image and measure the properties of more than 300 million celestial objects. The SDSS has imaged one-fifth of the sky and has discovered hundreds of thousands of galaxies, quasars, and stars. In addition to its imaging data, the SDSS has also obtained spectra for more than 3 million objects, making it one of the largest spectroscopic surveys ever undertaken.

The original goals of the SDSS were to map the large-scale structure of the Universe and to measure the physical properties (e.g., luminosities, sizes, masses, and chemical abundances) of a large sample of galaxies. These goals have been largely accomplished through two generations of surveys: The Legacy Survey (2000-2005), which mapped nearly 10,000 square degrees of sky in five optical bands (u*, g*, r*, i*, z*), and The Baryon Oscillation Spectroscopic Survey (BOSS; 2009-2014), which extended these measurements to higher redshifts using longer wavelength light collected with fiber optic cables attached to robotic positioners on 500 specially selected plates covering an additional 20% Ǟ sky area. A third generation survey called eBOSS will further extend these measurements by targeting tracers such as emission line galaxies, quasars, and Lyman alpha emitters out to redshifts z ~ 3 over an even larger fraction (~ 35%) Ǟof the sky.
In addition to its primary science goals described above related to cosmology and galaxy evolution physics, serendipitous discoveries made with SDSS data have led to fundamental advances across a wide range of astrophysical topics including solar system science , stellar astrophysics , Galactic archaeology , extragalactic transient science , time domain astronomy , near Earth object detection , circumstellar disk characterization around other stars similar to our own Sun .