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NGC 4457
NGC 4457 is an intermediate spiral galaxy located about 55 million light-years away in the constellation of Virgo. It is also classified as a LINER galaxy, a class of active galaxy defined by their spectral line emissions. NGC 4457 Is inclined by about 33°. It was discovered by astronomer William Herschel on February 23, 1784. Despite being listed in the Virgo Cluster Catalog as VCC 1145, NGC 4457 is a member of the Virgo II Groups which form an extension of the Virgo cluster. NGC 4457 may have had a recent minor merger with another galaxy. Supernova On July 1 2020, an astronomical transient was discovered in NGC 4457 by astronomer Kōichi Itagaki and confirmed by ASAS-SN. Spectroscopic classification determined the object to be a type Ia Supernova, designated SN2020nvb. Physical characteristics NGC 4457 has a broad oval zone containing an inner spiral which is defined mainly by two fairly open arms. There is a well-defined outer ring that is completely detached from t ... [...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 catalog, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Ia Supernova
A Type Ia supernova (read: "type one-A") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white dwarf. Physically, carbon–oxygen white dwarfs with a low rate of rotation are limited to below 1.44 solar masses (). Beyond this "critical mass", they reignite and in some cases trigger a supernova explosion; this critical mass is often referred to as the Chandrasekhar mass, but is marginally different from the absolute Chandrasekhar limit, where electron degeneracy pressure is unable to prevent catastrophic collapse. If a white dwarf gradually accretes mass from a binary companion, or merges with a second white dwarf, the general hypothesis is that a white dwarf's core will reach the ignition temperature for carbon fusion as it approaches the Chandrasekhar mass. Within a few seconds of initiation of nuclear fusion, a substant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Principal Galaxies Catalogue Objects
Principal may refer to: Title or rank * Principal (academia), the chief executive of a university ** Principal (education), the office holder/ or boss in any school * Principal (civil service) or principal officer, the senior management level in the UK Civil Service * Principal dancer, the top rank in ballet * Principal (music), the top rank in an orchestra Law * Principal (commercial law), the person who authorizes an agent ** Principal (architecture), licensed professional(s) with ownership of the firm * Principal (criminal law), the primary actor in a criminal offense * Principal (Catholic Church), an honorific used in the See of Lisbon Places * Principal, Cape Verde, a village * Principal, Ecuador, a parish Media * ''The Principal'' (TV series), a 2015 Australian drama series * ''The Principal'', a 1987 action film * Principal (music), the lead musician in a section of an orchestra * Principal photography, the first phase of movie production * "The Principal", a son ... [...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] |
LINER Galaxies
A low-ionization nuclear emission-line region (LINER) is a type of galactic nucleus that is defined by its spectral line emission. The spectra typically include line emission from weakly ionized or neutral atoms, such as O, O+, N+, and S+. Conversely, the spectral line emission from strongly ionized atoms, such as O++, Ne++, and He+, is relatively weak. The class of galactic nuclei was first identified by Timothy Heckman in the third of a series of papers on the spectra of galactic nuclei that were published in 1980. Demographics of LINER galaxies Galaxies that contain LINERs are often referred to as ''LINER galaxies''. LINER galaxies are very common; approximately one-third of all nearby galaxies (galaxies within approximately 20-40 Mpc) may be classified as LINER galaxies. Approximately 75% of LINER galaxies are either elliptical galaxies, lenticular galaxies, or S0/a-Sab galaxies ( spiral galaxies with large bulges and tightly wound spiral arms). LINERs ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intermediate Spiral Galaxies
An intermediate spiral galaxy is a galaxy A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar Sys ... 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 are. Examples References * Galaxy morphological types {{Spiral-galaxy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abell 2667
Abell 2667 is a galaxy cluster. It is one of the most luminous galaxy clusters in the X-ray waveband known at a redshift about 0.2. This cluster is also a well-known gravitational lens. On 2 March 2007, a team of astronomers reported the detection of the Comet Galaxy in this cluster. This galaxy is being ripped apart by the cluster's gravitational field and harsh environment. The finding sheds light on the mysterious process by which gas-rich spiral-shaped galaxies might evolve into gas-poor irregular- or elliptical-shaped galaxies over billions of years. See also * Abell catalogue * List of Abell clusters The Abell catalogue is a catalogue of approximately 4,000 galaxy clusters with at least 30 members, almost complete to a redshift of ''z'' = 0.2. It was originally compiled by the American astronomer George O. Abell in 1958 using plates from PO ... * X-ray astronomy References External links Hubble Space TelescopeSpitzer Space Telescope* {{DEFAULTSORT:Ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comet Galaxy
The Comet Galaxy, a spiral galaxy located 3.2 billion light-years from Earth, in the galaxy cluster Abell 2667, was found with the Hubble Space Telescope. This galaxy has slightly more mass than our Milky Way. It was detected on 2 March 2007. Structure This unique spiral galaxy, which is situated 3.2 billion light-years from the Earth, has an extended stream of bright blue knots and diffuse wisps of young stars. It rushes at 3.6 million km/h (1000km/s) through the cluster Abell 2667 and therefore, like a comet, shows a tail, with a length of 600,000 light-years. Galaxy fate The Сomet Galaxy is currently being ripped to pieces, moving through a cluster at speeds of greater than 2 million mph. As the galaxy speeds through, its gas and stars are being stripped away by the tidal forces exerted by the cluster. Also contributing to this destructive process is the pressure of the cluster's hot gas plasma reaching temperatures as high as 100 million degrees. Scientists estimate tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Messier 90
Messier 90 (also known as M90 and NGC 4569) is an intermediate spiral galaxy exhibiting a weak inner ring structure about 60 million light-years away in the constellation Virgo. It was discovered by Charles Messier in 1781. Membership of the Virgo Cluster Messier 90 is a member of the Virgo Cluster, being one of its largest and brightest spiral galaxies, with an absolute magnitude of around −22 (brighter than the Andromeda Galaxy). The galaxy is found about 1.5° from the central subgroup of Messier 87. Due to the galaxy's interaction with the intracluster medium in its cluster, the galaxy has lost much of its interstellar medium. As a result of this process, which is referred to as ram-pressure stripping, the medium and star formation regions appear severely truncated compared to similar galaxies outside the Virgo Cluster and there are even H II regions outside the galactic plane, as well as long (up to 80,000-parsec—that is, 260,000-light-year) tails of ionized ga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 NGC objects. The constellation information in these tables is taken from ''The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by Jjiko. L. E. Dreyer'', which was accessed using the "VizieR Service". Galaxy types are identified using the ''NASA/IPAC Extragalactic Database''. The other data of these tables are from the SIMBAD Astronomical Database unless otherwise stated. 4001–4100 4101–4200 4201-4300 4301–4400 4401–4500 4501–4600 4601–4700 4701–4800 4801–4900 4901–5000 See also * Lists of astronomical objects This is a list of lists, grouped by type of astronomical object. Solar System * List of Solar System objects * List of gravitationally rounded ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ram-pressure Stripping
Ram pressure is a pressure exerted on a body moving through a fluid medium, caused by relative bulk motion of the fluid rather than random thermal motion. It causes a drag force to be exerted on the body. Ram pressure is given in tensor form as :P_\text= \rho u_i u_j, where \rho is the density of the fluid; P_\text is the momentum flux per second in the i direction through a surface with normal in the j direction. u_i,u_j are the components of the fluid velocity in these directions. The total Cauchy stress tensor \sigma_ is the sum of this ram pressure and the isotropic thermal pressure (in the absence of viscosity). In the simple case when the relative velocity is normal to the surface, and momentum is fully transferred to the object, the ram pressure becomes :P_\text = \rho u^2. Derivation The Eulerian form of the Cauchy momentum equation for a fluid is :\rho\frac = -\vec \nabla p - \rho(\vec u \cdot \vec \nabla)\vec u + \rho \vec g for isotropic pressure p, where \v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intracluster Medium
In astronomy, the intracluster medium (ICM) is the superheated plasma that permeates a galaxy cluster. The gas consists mainly of ionized hydrogen and helium and accounts for most of the baryonic material in galaxy clusters. The ICM is heated to temperatures on the order of 10 to 100 megakelvins, emitting strong X-ray radiation. Composition The ICM is composed primarily of ordinary baryons, mainly ionised hydrogen and helium. This plasma is enriched with heavier elements, including iron. The average amount of heavier elements relative to hydrogen, known as metallicity in astronomy, ranges from a third to a half of the value in the sun. Studying the chemical composition of the ICMs as a function of radius has shown that cores of the galaxy clusters are more metal rich than at larger radii. In some clusters (e.g. the Centaurus cluster) the metallicity of the gas can rise to above that of the sun. Due to the gravitational field of clusters, metal-enriched gas ejected from supernova ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
