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In 2016, the International Astronomical Union (IAU) organized a Working Group on Star Names (WGSN) [2] to catalog and standardize proper names for stars. The WGSN's first bulletin, dated July 2016, [3] included a table of 125 stars comprising the first two batches of names approved by the WGSN (on 30 June and 20 July 2016) together with names of stars adopted by the IAU Executive Committee ...
Rings. Galaxies are divided into those possessing ring-like structures (denoted ‘(r)’) and those without rings (denoted ‘(s)’). So-called ‘transition’ galaxies are given the symbol (rs). [16] Spiral arms. As in Hubble’s original scheme, spiral galaxies are assigned to a class based primarily on the tightness of their spiral arms.
A primary star, which is brighter and typically bigger than its companion stars, is designated by a capitalized A. Its companions are labelled B, C, and so on. For example, Sirius, the brightest star in the sky, is actually a double star, consisting of the naked-eye visible Sirius A and its dim white-dwarf companion Sirius B.
The spectral class of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan–Keenan (MK) system using the letters O, B, A, F, G, K, and M, a sequence from the hottest (O type) to the coolest (M type).
Radio-faint galaxies like M 31 and M33, the Milky Way's neighbors, have weaker fields (about 5 μG), while gas-rich galaxies with high star-formation rates, like M 51, M 83 and NGC 6946, have 15 μG on average. In prominent spiral arms, the field strength can be up to 25 μG, in regions where cold gas and dust are also concentrated.
IC – (celestial object) Intracluster, either the regions between stars in star clusters or the region between galaxies in galaxy clusters; ICE – (spacecraft) International Comet Explorer; ICM – (celestial object) intracluster medium, is the superheated gas present at the center of a galaxy cluster; ICQ – (publication) International ...
The characteristics of Seyfert galaxies were first observed in M77 in 1908; however, Seyferts were defined as a class in 1943. [23] First radio galaxy: Cygnus A: Cygnus: 1951 Of several items, then called radio stars, Cygnus A was identified with a distant galaxy, being the first of many radio stars to become a radio galaxy. [24] [25] First ...
Z — Fritz Zwicky, Catalogue of galaxies and of clusters of galaxies; ZC — Robertson's Zodiacal Catalogue (James Robertson's catalogue of 3539 zodiacal stars brighter than 9th magnitude) Zij — Islamic astronomical books that tabulates parameters used for astronomical calculations of the positions of the Sun, Moon, stars, and planets