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Fanaroff–Riley Classification
The Fanaroff–Riley classification is a scheme created by B.L. Fanaroff and J.M. Riley in 1974, which is used to distinguish radio galaxies with active nuclei based on their radio luminosity or brightness of their radio emissions in relation to their hosting environment. Fanaroff and Riley noticed that the relative positions high/low surface brightness regions in the lobes of extragalactic radio sources are correlated with their radio luminosity. Their conclusion was based on a set of 57 radio galaxies and quasars that were clearly resolved at 1.4 GHz or 5 GHz into two or more components. Fanaroff and Riley divided this sample into two classes using the ratio of the distance between the regions of highest surface brightness on opposite sides of the central galaxy or quasar to the total extent of the source up to the lowest brightness contour. ''Class I'' (abbreviated FR-I) are sources whose luminosity decreases as the distance from the central galaxy or quasar host in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bernie Fanaroff
Bernard Lewis Fanaroff (born 1947) is a South African astronomer and trade unionist. He served in several positions in the South African government from 1994 to 2000 related to the Reconstruction and Development Programme, the RDP, and to Safety and Security.From 2003 to 2015 he led South Africa's bid to host the Square Kilometre Array Radio Telescope, the SKA, in Africa and the design and construction of the MeerKAT radio telescope. He is the co-developer of the Fanaroff–Riley classification, a method of classifying radio galaxies. He was the Project Director of South Africa's Square Kilometre Array bid. Education and early life Fanaroff was born in Johannesburg, South Africa, to parents of Latvian and Lithuanian Jewish origins, and attended Northview High School. He completed a BSc.Hons (Physics) in 1970 at the University of the Witwatersrand (WITS) and a PhD in Radio Astronomy from the University of Cambridge in 1974. While working on his PhD and in collaboration with B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Julia Riley
Julia M. Riley (née Hill) is a British astrophysicist who developed the Fanaroff–Riley classification. Personal and professional background She is the daughter of Philippa (born Pass) and British marine geophysicist Maurice Hill and granddaughter of Nobel Prize–winning physiologist Archibald Vivian Hill. Riley is a Fellow of Girton College associated with the Cavendish Astrophysics Group at University of Cambridge. Her primary field of research is in the area of radio astronomy. Riley lectures and supervises physics within the Natural Sciences Tripos at the University of Cambridge. Fanaroff–Riley type I and II In 1974, along with Fanaroff, she wrote a paper classifying radio galaxies into two types based on their morphology (shape). Fanaroff and Riley's classification became known as Fanaroff–Riley type I and II of radio galaxies (FRI and FRII). In FRI sources the major part of the radio emission comes from closer to the centre of the source, whereas in FRII so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monthly Notices Of The Royal Astronomical Society
''Monthly Notices of the Royal Astronomical Society'' (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics. It has been in continuous existence since 1827 and publishes letters and papers reporting original research in relevant fields. Despite the name, the journal is no longer monthly, nor does it carry the notices of the Royal Astronomical Society. History The first issue of MNRAS was published on 9 February 1827 as ''Monthly Notices of the Astronomical Society of London'' and it has been in continuous publication ever since. It took its current name from the second volume, after the Astronomical Society of London became the Royal Astronomical Society (RAS). Until 1960 it carried the monthly notices of the RAS, at which time these were transferred to the newly established ''Quarterly Journal of the Royal Astronomical Society'' (1960–1996) and then to its successor journal ''Astronomy & Geophysics'' (since 1997). Until 1965, MNRAS ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Galaxy
A radio galaxy is a galaxy with giant regions of radio emission extending well beyond its visible structure. These energetic radio lobes are powered by jets from its active galactic nucleus. They have luminosities up to 1039 W at radio wavelengths between 10 MHz and 100 GHz. The radio emission is due to the synchrotron process. The observed structure in radio emission is determined by the interaction between twin jets and the external medium, modified by the effects of relativistic beaming. The host galaxies are almost exclusively large elliptical galaxies. ''Radio-loud'' active galaxies can be detected at large distances, making them valuable tools for observational cosmology. Recently, much work has been done on the effects of these objects on the intergalactic medium, particularly in galaxy groups and clusters. Alcyoneus is a low-excitation radio galaxy, identified as having the largest radio lobes found, with lobed structures spanning 5 megaparsecs (16×1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Galactic Nucleus
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. Such excess non-stellar emission has been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an "active galaxy". The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy. Active galactic nuclei are the most luminous persistent sources of electromagnetic radiation in the universe, and as such can be used as a means of discovering distant objects; their evolution as a function of cosmic time also puts constraints on models of the cosmos. The observed characteristics of an AGN depend on several properties such as the mass of the central black hole, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Luminosity
Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a star, galaxy, or other astronomical object. In SI units, luminosity is measured in joules per second, or watts. In astronomy, values for luminosity are often given in the terms of the luminosity of the Sun, ''L''⊙. Luminosity can also be given in terms of the astronomical magnitude system: the absolute bolometric magnitude (''M''bol) of an object is a logarithmic measure of its total energy emission rate, while absolute magnitude is a logarithmic measure of the luminosity within some specific wavelength range or filter band. In contrast, the term ''brightness'' in astronomy is generally used to refer to an object's apparent brightness: that is, how bright an object appears to an observer. Apparent brightness depends on both the lumin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Waves
Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (shorter than a grain of rice); at 30 Hz the corresponding wavelength is (longer than the radius of the Earth). Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a close, but slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects. Radio waves are generated artificially by an electronic device called a transmitter, which is connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver, which p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ram Pressure
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] |
Relativistic Beaming
Relativistic beaming (also known as Doppler beaming, Doppler boosting, or the headlight effect) is the process by which relativistic effects modify the apparent luminosity of emitting matter that is moving at speeds close to the speed of light. In an astronomical context, relativistic beaming commonly occurs in two oppositely-directed relativistic jets of plasma that originate from a central compact object that is accreting matter. Accreting compact objects and relativistic jets are invoked to explain x-ray binaries, gamma-ray bursts, and, on a much larger scale, active galactic nuclei (quasars are also associated with an accreting compact object, but are thought to be merely a particular variety of active galactic nuclei, or AGNs). Beaming affects the apparent brightness of a moving object. Consider a cloud of gas moving relative to the observer and emitting electromagnetic radiation. If the gas is moving towards the observer, it will be brighter than if it were at rest, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
3C 47 Quasar FR-II
3C may refer to: In astronomy: * 3C, the ''Third Cambridge Catalogue of Radio Sources'', an astronomical reference series In business: * Long March 3C, a 2008 Chinese orbital rocket * 3C Records, a record label * 3C (radio), a defunct digital radio station * Team 3C Casalinghi Jet Androni Giocattoli, a defunct Italian professional cycling team * 3C, the IATA code for defunct American airline RegionsAir * Three-cent piece * 3C (trade association) 3C, also styled the Connected Commerce Council, is a Washington, DC-based small business advocacy organization. It receives significant funding from large tech firms such as Google and Amazon. History 3C was founded in 2018 by Jake Ward to “pro ... is an American trade association. In computing: * Three Cs (Compulsory, Capacity, and Conflict), three categories of CPU cache misses * 3C, or Computer Control Company, Inc., a pioneering minicomputer company (1953–1966) * Agile software development, Agile model: 3C (Card, Conversation, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
