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NGC 4889 (also known as Caldwell 35, Coma B) is a class-4 supergiant elliptical galaxy. It was discovered in 1785 by the British astronomer Frederick William Herschel I, who catalogued it as a bright, nebulous patch. The brightest galaxy within the northern Coma Cluster, it is located at a distance of 94 million parsecs (308 million light years) from Earth. Unlike a flattened, disc-shaped spiral galaxy like the Milky Way, NGC 4889 has no visible dust lanes or spiral arms and has a smooth, featureless, egg-shaped profile that diminishes in luminosity with distance from the center. At the core of the galaxy is a supermassive black hole that heats up the intracluster medium through the action of friction from infalling gases and dust. The X-ray emission from the galaxy extends out to several million light years of the cluster. As with other similar elliptical galaxies, only a fraction of the mass of NGC 4889 is in the form of stars. They have a flattened, unequal distribution that bulges within its edge. Between the stars is a dense interstellar medium full of heavy elements emitted by evolved stars. In addition it also has a diffuse stellar halo that extends out to one million light years in diameter. Orbiting the galaxy is a very large population of globular clusters. NGC 4889 is also a strong source of soft X-ray, ultraviolet, and radio frequency radiation. As the largest and the most massive galaxy easily visible to Earth, NGC 4889 has played an important role in both amateur and professional astronomy, and has become a prototype in studying the dynamical evolution of other supergiant elliptical galaxies in the more distant universe. ==Observation== NGC 4889 was not included by the French astronomer Charles Messier in his famous Messier catalogue despite being an intrinsically bright object quite close to some Messier objects. The first known observation of NGC 4889 was that of Frederick William Herschel I, assisted by his sister, Caroline Lucretia Herschel, in 1785, who included it in the Catalogue of Nebulae and Clusters of Stars published a year later. In 1864, Herschel's son, John Frederick William Herschel, published the General Catalogue of Nebulae and Clusters of Stars. He included the objects catalogued by his father, including the later to be called NGC 4889, plus other objects he found that were somehow missed by his father. In 1888 the Danish-Irish astronomer John Louis Emil Dreyer published the New General Catalogue of Nebulae and Clusters of Stars (NGC), with a total of 7,840 objects, but he erroneously duplicated the galaxy in two designations, NGC 4884 and NGC 4889. Within the following century, several projects aimed to revise the NGC catalogue were conducted, such as The NGC/IC Project, Revised New General Catalogue of Nebulae and Clusters of Stars, and the NGC 2000.0 projects, discovered the duplication. It was then decided that the object to be called by its latter designation, NGC 4889, which is in use today. In December 1995, Patrick Caldwell Moore compiled the Caldwell catalogue, a list of 109 persistent, bright objects that were somehow missed by Messier in his catalogue. The list also includes NGC 4889, which is given the designation Caldwell 35. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「NGC 4889」の詳細全文を読む スポンサード リンク
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