Stjernekataloger

Stjernekataloger are systematic listings of stars and stellar properties compiled by astronomers. They range from historical inventories used for navigation to modern, multi-wavelength datasets containing hundreds of millions of objects. The term stjernekataloger is used in Scandinavian languages to refer to such catalogs.

Typically an entry in a stjernekatalog lists an identifier, celestial coordinates, epoch, and a set of measured properties such as apparent magnitude, color indices, spectral type, parallax and proper motion. Many catalogs also include photometric bands, radial velocity, angular separation from companions, variability information, and cross-identifications with other catalogs.

Historical catalogs include Ptolemy’s Almagest and the Bayer and Flamsteed star catalogs, while modern catalogs are generated by large sky surveys. Notable examples are Hipparcos, its Tycho-2 successor, Gaia (with successive data releases), 2MASS, UCAC, and SDSS. Modern catalogs can contain billions of entries and are often multi-wavelength.

Stjernekataloger support a wide range of astronomical activities, including astrometry, calibration of telescopes, cross-matching objects between surveys, and studies of stellar populations and Galactic structure. Access is provided through online services such as VizieR, SIMBAD, Gaia Archive, and observatory data portals, which offer search, cross-identification, and data retrieval.

Coordinates are usually given in standard systems such as the International Celestial Reference System (ICRS) with equinox J2000.0, and may include epoch-specific proper motions. Cross-identification and homogeneous data calibration are ongoing challenges due to varying measurement methods and selection effects.