Galaxy: Difference between revisions

Millions of galaxies have been catalogued, but [[List of galaxies#Named galaxies|only a few]] have well-established names, such as the [[Andromeda Galaxy]], the [[Magellanic Clouds]], the [[Whirlpool Galaxy]], and the [[Sombrero Galaxy]]. Astronomers work with numbers from certain catalogues, such as the [[Messier catalogue]], the NGC ([[New General Catalogue]]), the IC ([[Index Catalogue]]), the CGCG ([[Catalogue of Galaxies and of Clusters of Galaxies]]), the MCG ([[Morphological Catalogue of Galaxies]]), the UGC ([[Uppsala General Catalogue]] of Galaxies), and the PGC ([[Catalogue of Principal Galaxies]], also known as LEDA). All the well-known galaxies appear in one or more of these catalogscatalogues but each time under a different number. For example, [[Messier 109]] (or "M109") is a spiral galaxy having the number 109 in the catalogcatalogue of Messier. It also has the designations NGC 3992, UGC 6937, CGCG 269–023, MCG +09-20-044, and PGC 37617 (or LEDA 37617), among others.<ref>{{cite web|url=https://ned.ipac.caltech.edu/byname?objname=M109&hconst=67.8&omegam=0.308&omegav=0.692&wmap=4&corr_z=1 |title=Results for object MESSIER 109 (M109)| publisher=[[California Institute of Technology]]|website=[[NASA/IPAC Extragalactic Database]] |access-date=2023-01-13}}</ref> Millions of fainter galaxies are known by their identifiers in [[sky surveys]] such as the [[Sloan Digital Sky Survey]].<ref>{{Cite web |title=What is the Sloan Digital Sky Survey?|url=https://skyserver.sdss.org/dr7/en/sdss/ |archive-url=https://web.archive.org/web/20240112203017/https://skyserver.sdss.org/dr7/en/sdss/ |archive-date=2024-01-12 |access-date=2024-03-03 |website=[[Sloan Digital Sky Survey]]}}</ref>