| 单词 | ngc | ||||||||||||||||||||||||||||||||||||||||||
| 释义 | NGCNGCNGCNGCNGCShort for New General Catalogue of Nebulae and Clusters of Stars, prepared by the Danish astronomer J.L.E. Dreyer at Armagh Observatory, Ireland, and published in 1888. It was based on an earlier General Catalogue of Nebulae and Clusters of Stars (GC),compiled in 1864 by Sir John Herschel from his own observations and previous catalogs by his father and aunt, Sir William and Caroline Herschel. Dreyer's work listed 7840 currently known nonstellar objects – nebulae, clusters, and galaxies (although the galaxies were not yet identified as such). Each object is numbered by right ascension and its position and description given. The number is preceded by the letters NGC; this is the object's NGC number, an example being NGC 1976: the Orion nebula. Some of the brightest NGC objects also appear in the Messier Catalog.Dreyer listed 5386 further discoveries in two supplements to the original NGC. These were the first and second Index Catalogs (IC), published in 1895 and 1908. The three catalogs, now published as one volume, cover the whole sky. The NGC underwent several revisions during its first hundred years. In 1988, on the centenary of Dreyer's original publication, Roger Sinnott published NGC 2000.0, a version of the NGC and IC containing the positions of 13 226 objects for the epoch 2000.0. In 2001 Wolfgang Steinicke produced a more thorough revision, adding a further 767 objects. The NGC/IC Project, accessible over the World Wide Web, seeks to eliminate observing errors and misidentifications inherent in Dreyer's original work to arrive at a clean version of the NGC and IC, with each object unambiguously numbered and identified and correctly attributed to its discoverer. NGC
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英语词典包含2567994条英英释义在线翻译词条，基本涵盖了全部常用单词的英英翻译及用法，是英语学习的有利工具。