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The Swift UVOT Photometric System
The Ultraviolet and Optical Telescope (UVOT) is one of three instruments on board the Neil Gehrels Swift Observatory that observes astronomical objects in its 17-by-17 arc minute field of view through one of several filters or grisms. The seven filters, which are similar to those on the XMM-Newton Optical Monitor instrument, cover the near-ultraviolet and optical range. The brightness of an object observed in the three optical filters, called u, b, and v, can be converted into the more common Johnson-Morgan (see the UBV photometric system) magnitudes. The three ultraviolet filters probe a spectral region that is not observable from the ground. Although Swift's main mission is to chase gamma-ray bursts as soon as they occur, UVOT has been used to observe and measure many other transient celestial sources as well. The filters, not being like any other photometric system in use from the ground or in space, give unique photometric measurements. Their response has been defined as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neil Gehrels Swift Observatory
Neil Gehrels Swift Observatory, previously called the Swift Gamma-Ray Burst Explorer, is a NASA three-telescope space observatory for studying gamma-ray bursts (GRBs) and monitoring the afterglow in X-ray, and UV/Visible light at the location of a burst. It was launched on 20 November 2004, aboard a Delta II launch vehicle. Headed by principal investigator Neil Gehrels until his death in February 2017, the mission was developed in a joint partnership between Goddard Space Flight Center (GSFC) and an international consortium from the United States, United Kingdom, and Italy. The mission is operated by Pennsylvania State University as part of NASA's Medium Explorer program (MIDEX). The burst detection rate is 100 per year, with a sensitivity ~3 times fainter than the BATSE detector aboard the Compton Gamma Ray Observatory. The Swift mission was launched with a nominal on-orbit lifetime of two years. Swift is a NASA MIDEX (medium-class Explorer) mission. It was the third t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transient Astronomical Event
The asterisk ( ), from Late Latin , from Ancient Greek , ''asteriskos'', "little star", is a typographical symbol. It is so called because it resembles a conventional image of a heraldic star. Computer scientists and mathematicians often vocalize it as star (as, for example, in ''the A* search algorithm'' or ''C*-algebra''). In English, an asterisk is usually five- or six-pointed in sans-serif typefaces, six-pointed in serif typefaces, and six- or eight-pointed when handwritten. Its most common use is to call out a footnote. It is also often used to censor offensive words. In computer science, the asterisk is commonly used as a wildcard character, or to denote pointers, repetition, or multiplication. History The asterisk has already been used as a symbol in ice age cave paintings. There is also a two thousand-year-old character used by Aristarchus of Samothrace called the , , which he used when proofreading Homeric poetry to mark lines that were duplicated. Origen is know ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sistema Fotométrico UBV
AFK Sistema PAO is a large Russian conglomerate company, founded by Vladimir Yevtushenkov, who was chairman of the corporation's board of directors until 2022. In April, Yevtushenkov's shareholding in Sistema has decreased to 49.2%, and he also stepped down from Sistema's board. Sistema has its headquarters in Moscow. The company's global depository receipts (GDRs) are traded on the London Stock Exchange (ticker symbol ). History In 1993, Evgeny Novitsky and Vladimir Yevtushenkov founded the holding company AFK Sistema, also known as Sistema JSFC, to group together several information technology (IT) and cell phone companies including MTS. Structure Sistema operates a number of consumer service businesses in the areas of: * IT and telecoms — Mobile TeleSystems, Moscow City Telephone Network, SkyLink, Sitronics (formerly known as 'Science Center Concern'), NIIME, Mikron, STROM telecom. * Banking — :ru:МТС Банк, MTS Bank * E-commerce – Ozon (company), Ozon * House-B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sistem Fotometrik UBV
"Let Me Try" is a song recorded by Romanian singer Luminița Anghel and Romanian percussion band Sistem, consisting of Toth Zoltan, Mihai Ciprian Rogojan, Claudiu Purcărin, Robert Magheti and Florin Cătălin Romașcu. It was released as a CD single in 2005 by the Romanian Television (TVR). Romanian composer Cristian Faur wrote and produced the single for Anghel, who subsequently recorded it in collaboration with Sistem. Musically, "Let Me Try" is an uptempo folk-influenced disco song. The track in the Eurovision Song Contest 2005 in Kyiv, Ukraine after winning the pre-selection show ''Selecția Națională''. Anghel and Sistem's win was surrounded by controversy after the second-placed Romanian singer Loredana Groza accused TVR of conspiracy and arranged voting. In Kyiv, the artists qualified in first place for the Grand Final, where they came in third place with a total of 158 points. This remains Romania's best placement to date, alongside 's " Playing with Fire" by Paula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photometric Systems
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Photometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an astronomical object's electromagnetic radiation * Spectrophotometry, the measurement of spectral distribution along with the flux or intensity * A photometric study, sometimes also referred to as a lighting "layout" or "point by point" *Photometric stereo, a computer vision technique for estimating 3D shape from one or more images. See also * Photogrammetry * Radiometry Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Classification
In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The ''spectral class'' of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan–Keenan (MK) system using the letters ''O'', ''B'', ''A'', ''F'', ''G'', ''K'', and ''M'', a sequence from the hottest (''O'' type) to the coolest (''M'' type). Each letter class is then subdivi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Outer Space
Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays. The baseline temperature of outer space, as set by the background radiation from the Big Bang, is . The plasma between galaxies is thought to account for about half of the baryonic (ordinary) matter in the universe, having a number density of less than one hydrogen atom per cubic metre and a kinetic temperature of millions of kelvins. Local concentrations of matter have condensed into stars and galaxies. Studies indicate that 90% of the mass in most galaxies is in an unknown form, called dark matter, which interacts with other matter through gravitational but not electromagnetic forces. Observations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photometric System
In astronomy, a photometric system is a set of well-defined passbands (or optical filters), with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric system a set of primary standard stars is provided. A commonly adopted standardized photometric system is the Johnson-Morgan or UBV photometric system (1953). At present, there are more than 200 photometric systems. Photometric systems are usually characterized according to the widths of their passbands: * broadband (passbands wider than 30 nm, of which the most widely used is Johnson-Morgan UBV system) * intermediate band (passbands between 10 and 30 nm wide) * narrow band (passbands less than 10 nm wide) Photometric letters Each letter designates a section of light of the electromagnetic spectrum; these cover well the consecutive major groups, near-ultraviolet (NUV), visible light (centered on the V band), near-infra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma-ray Burst
In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten milliseconds to several hours. After an initial flash of gamma rays, a longer-lived "afterglow" is usually emitted at longer wavelengths (X-ray, ultraviolet, optical, infrared, microwave and radio). The intense radiation of most observed GRBs is thought to be released during a supernova or superluminous supernova as a high-mass star implodes to form a neutron star or a black hole. A subclass of GRBs appear to originate from the merger of binary neutron stars. The sources of most GRBs are billions of light years away from Earth, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the Sun will in its entire 10-billion-year lifetime) and extremely rare (a few per galaxy per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Object
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often used interchangeably. However, an astronomical body or celestial body is a single, tightly bound, contiguous entity, while an astronomical or celestial ''object'' is a complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures. Examples of astronomical objects include planetary systems, star clusters, nebulae, and galaxies, while asteroids, moons, planets, and stars are astronomical bodies. A comet may be identified as both body and object: It is a ''body'' when referring to the frozen nucleus of ice and dust, and an ''object'' when describing the entire comet with its diffuse coma and tail. History Astronomical objects such as stars, planets, nebulae, asteroids and comet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnitude (astronomy)
In astronomy, magnitude is a unitless measure of the brightness of an object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths. An imprecise but systematic determination of the magnitude of objects was introduced in ancient times by Hipparchus. The scale is logarithmic and defined such that a magnitude 1 star is exactly 100 times brighter than a magnitude 6 star. Thus each step of one magnitude is \sqrt \approx 2.512 times brighter than the magnitude 1 higher. The brighter an object appears, the lower the value of its magnitude, with the brightest objects reaching negative values. Astronomers use two different definitions of magnitude: apparent magnitude and absolute magnitude. The ''apparent'' magnitude () is the brightness of an object as it appears in the night sky from Earth. Apparent magnitude depends on an object's intrinsic luminosity, its distance, and the extinction reducing its brightness. The ''absolute'' magnitu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
