SDSS

SDSS stands for Sloan Digital Sky Survey, a major astronomical survey that has produced detailed imaging and spectroscopy of large areas of the sky. Initiated in 2000, it is conducted with a dedicated 2.5-meter telescope at Apache Point Observatory in New Mexico. The project collects wide-field imaging in five filters and follow-up spectroscopy for selected objects, enabling three-dimensional maps of the universe through precise redshifts.

SDSS data have led to catalogs of millions of stars, galaxies, and quasars, and have informed studies of galaxy evolution, the large-scale structure of the cosmos, and the history of the Milky Way. The imaging data allow morphological and photometric classifications, while spectroscopic measurements provide redshifts and physical properties. The data are released publicly through a series of data releases and are accessible via the project’s SkyServer portal.

SDSS has progressed through several phases (SDSS-I/II, SDSS-III, SDSS-IV, and SDSS-V), with collaborations among universities and research institutions worldwide. Its legacy includes large-scale measurements of baryon acoustic oscillations and constraints on dark energy, as well as extensive catalogs used across astronomy. The project continues to expand to time-domain observations and mapping of the Milky Way and nearby galaxies.