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NGC 4818
NGC 4818 is a spiral galaxy in the constellation Virgo. The galaxy lies about 45 million light years away from Earth, which means, given its apparent dimensions, that NGC 4818 is approximately 55,000 light years across. It was discovered by William Herschel on March 3, 1786. NGC 4818 has an elliptical bulge with a bright nucleus. The galaxy has a bar which appears about 30 degrees offset from the major axis of the bulge. Some loosely wrapped spiral arms emerge from the bulge. A faint disk with a low contrast broad spiral pattern is seen surrounding the bulge, aligned with the major axis of the elliptical bulge. The spectrum of the nucleus is similar to that of an HII region. The total star formation rate is estimated to be 0.7 per year. The total gas mass is estimated to be while the total star mass is about . A. M. Garcia considers the galaxy to be a member of the NGC 4699 Group, or LGG 307. Other members of that group include NGC 4699, NGC 4700, NGC 4722, NGC 4742, N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
New General Catalogue
The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxy, galaxies, star clusters and emission nebulae. Dreyer published two supplements to the NGC in 1895 and 1908, known as the ''Index Catalogues'' (abbreviated IC), describing a further 5,386 astronomical objects. Thousands of these objects are best known by their NGC or IC numbers, which remain in widespread use. The NGC expanded and consolidated the cataloguing work of William Herschel, William and Caroline Herschel, and John Herschel's ''General Catalogue of Nebulae and Clusters of Stars''. Objects south of the Celestial sphere, celestial equator are catalogued somewhat less thoroughly, but many were included based on observation by John Herschel or James Dunlop. The NGC contained multiple errors, but attempts to eliminate them were made by the ''Revised New Ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star Formation
Star formation is the process by which dense regions within molecular clouds in interstellar space—sometimes referred to as "stellar nurseries" or "star-forming regions"—Jeans instability, collapse and form stars. As a branch of astronomy, star formation includes the study of the interstellar medium (ISM) and giant molecular clouds (GMC) as precursors to the star formation process, and the study of protostars and young stellar objects as its immediate products. It is closely related to planet formation, another branch of astronomy. Star formation theory, as well as accounting for the formation of a single star, must also account for the statistics of binary stars and the initial mass function. Most stars do not form in isolation but as part of a group of stars referred as star clusters or stellar associations. First stars Star formation is divided into three groups called "Populations". Population III stars formed from primordial hydrogen after the Big Bang. These stars are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Markarian Galaxies
The Markarian galaxies are a class of galaxies that have nuclei with excessive amounts of ultraviolet emissions compared with other galaxies. Benjamin Markarian drew attention to these types of galaxies starting in 1963. The nuclei of the galaxies had a blue colour, associated to stars in the classes from O to A. This blue core did not match the rest of the galaxy. The spectrum in detail tends to show a continuum that Markarian concluded was produced non- thermally. Most of these have emission lines and are characterized by highly energetic activity. Markarian Catalogue entries are of the form "Markarian ####", and can frequently use the abbreviations Mrk, Mkr, Mkn; and rarely Ma, Mk, Mark. History In 1964 Markarian decided to search for this kind of galaxy. The First Byurakan Survey commenced in 1965 using the Schmidt telescope at the Byurakan Astrophysical Observatory in Armenian SSR. The telescope used a 132 cm mirror and 102 cm correcting plate. When this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC Objects
The ''New General Catalogue of Nebulae and Clusters of Stars'' (abbreviated NGC) is an astronomical catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888. The NGC contains 7,840 objects, including galaxies, star clusters and emission nebulae. Dreyer published two supplements to the NGC in 1895 and 1908, known as the ''Index Catalogues'' (abbreviated IC), describing a further 5,386 astronomical objects. Thousands of these objects are best known by their NGC or IC numbers, which remain in widespread use. The NGC expanded and consolidated the cataloguing work of William and Caroline Herschel, and John Herschel's '' General Catalogue of Nebulae and Clusters of Stars''. Objects south of the celestial equator are catalogued somewhat less thoroughly, but many were included based on observation by John Herschel or James Dunlop. The NGC contained multiple errors, but attempts to eliminate them were made by the ''Revised New General Catalogue'' (RNGC) by Jack W. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peculiar Galaxies
A peculiar galaxy is a galaxy A galaxy is a Physical system, system of stars, stellar remnants, interstellar medium, interstellar gas, cosmic dust, dust, and dark matter bound together by gravity. The word is derived from the Ancient Greek, Greek ' (), literally 'milky', ... of unusual size, shape, or composition. Between five and ten percent of known galaxies are categorized as peculiar. Astronomers have identified two types of peculiar galaxies: ''interacting galaxies'' and ''active galactic nuclei'' (AGN). When two galaxies come close to each other, their mutual gravitational forces can cause them to acquire highly irregular shapes. The terms 'peculiar galaxy' and 'interacting galaxy' have now become synonymous because the majority of peculiar galaxies attribute their forms to such gravitational forces. Formation Scientists hypothesize that many peculiar galaxies are formed by the collision of two or more galaxies. As such, peculiar galaxies tend to host more activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intermediate Spiral Galaxies
An intermediate spiral galaxy is a galaxy that is in between the classifications of a barred spiral galaxy and an unbarred spiral galaxy. It is designated as SAB in the galaxy morphological classification system devised by Gerard de Vaucouleurs. Subtypes are labeled as SAB0, SABa, SABb, or SABc, following a sequence analogous to the Hubble sequence for barred and unbarred spirals. The subtype (0, a, b, or c) is based on the relative prominence of the central bulge and how tightly wound the spiral arms Spiral arms are a defining feature of spiral galaxies. They manifest as spiral-shaped regions of enhanced brightness within the galactic disc. Typically, spiral galaxies exhibit two or more spiral arms. The collective configuration of these arms ... are. Examples References * Galaxy morphological types {{Spiral-galaxy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virgo Cluster
The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc) away in the Virgo constellation. Comprising approximately 1,300 (and possibly up to 2,000) member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group (containing the Milky Way galaxy) is a member. The Local Group actually experiences the mass of the Virgo Supercluster as the Virgocentric flow. It is estimated that the Virgo Cluster's mass is 1.2 out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc. Many of the brighter galaxies in this cluster, including the giant elliptical galaxy Messier 87, were discovered in the late 1770s and early 1780s and subsequently included in Charles Messier's catalogue of non-cometary fuzzy objects. Described by Messier as nebulae without stars, their true nature was not recognized until the 1920s. The cluster extends across approximately 8 degrees centered in the constellation Virgo. Some of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sombrero Galaxy
The Sombrero Galaxy (also known as Messier Object 104, M104 or NGC 4594) is a peculiar galaxy of unclear classification in the constellation borders of Virgo and Corvus, being about from the Milky Way galaxy. It is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. It has an isophotal diameter of approximately , making it slightly bigger in size than the Milky Way. It has a bright nucleus, an unusually large central bulge, and a prominent dust lane in its outer disk, which from Earth is viewed almost edge-on. The dark dust lane and the bulge give it the appearance of a sombrero hat (thus the name). Astronomers initially thought the halo was small and light, indicative of a spiral galaxy; but the Spitzer Space Telescope found that the halo was significantly larger and more massive than previously thought, indicative of a giant elliptical galaxy. The galaxy has an apparent magnitude of + ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 4802
NGC may refer to: Companies * NGC Corporation, the name of US electric company Dynegy, Inc. from 1995 to 1998 * National Gas Company of Trinidad and Tobago, a state-owned natural gas company in Trinidad and Tobago * National Grid plc, a former name of National Grid Electricity Transmission plc, the operator of the British electricity transmission system * Northrop Grumman Corporation, an aerospace and defense conglomerate formed from the merger of Northrop Corporation and Grumman Corporation in 1994 * Numismatic Guaranty Company, a coin certification company in the United States * National Garden Clubs, headquartered in St. Louis, Missouri * Network General Corporation, a defunct networking hardware company Other uses * National Gallery of Canada, an art gallery founded in 1880 in Ottawa, Canada * National Games of China, the national multi-sport event of China * National Geographic (American TV channel), a documentary and reality television channel established in the United States ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 4790
NGC 4790 is a barred spiral galaxy located in the constellation of Virgo. Its velocity with respect to the cosmic microwave background is 1679 ± 24km/s, which corresponds to a Hubble distance of . In addition, six ''non-redshift'' measurements give a distance of . It was discovered on 25 March 1786 by German-British astronomer William Herschel. NGC 4790 is a member of the NGC 4699 Group (also known as LGG 307) of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. One supernova has been observed in NGC 4790. SN 2012au ( typeIb, mag. 13.8) was discovered by the Catalina Sky Survey on 14 March 2012. This supernova later produced evidence of a pulsar wind nebula which appears to be expanding outward at approximately 2300 km/s. See also * List of NGC objects (4001–5000) *Extragalactic astronomy Extragalactic astronomy is the branch of astronomy concerned with objects outside ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 4781
NGC 4781 is a barred spiral galaxy in the constellation Virgo. It was discovered by William Herschel on Mar 25, 1786. It is a member of the NGC 4699 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. See also * List of NGC objects (4001–5000) This is a list of NGC objects 4001–5000 from the New General Catalogue (NGC). The astronomical catalogue is composed mainly of star clusters, nebulae, and galaxies. Other objects in the catalogue can be found in the other subpages of the list of ... References External links * Barred spiral galaxies Virgo (constellation) 4781 043902 {{Spiral-galaxy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 4742
NGC may refer to: Companies * NGC Corporation, the name of US electric company Dynegy, Inc. from 1995 to 1998 * National Gas Company of Trinidad and Tobago, a state-owned natural gas company in Trinidad and Tobago * National Grid plc, a former name of National Grid Electricity Transmission plc, the operator of the British electricity transmission system * Northrop Grumman Corporation, an aerospace and defense conglomerate formed from the merger of Northrop Corporation and Grumman Corporation in 1994 * Numismatic Guaranty Company, a coin certification company in the United States * National Garden Clubs, headquartered in St. Louis, Missouri * Network General Corporation, a defunct networking hardware company Other uses * National Gallery of Canada, an art gallery founded in 1880 in Ottawa, Canada * National Games of China, the national multi-sport event of China * National Geographic (American TV channel), a documentary and reality television channel established in the United States ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
