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Spinning Dust
In astronomy, spinning dust emission is a mechanism proposed to explain anomalous microwave emission from the Milky Way. The emission could arise from the electric dipole of very rapidly spinning (10–60 GHz) extremely small (nanometer) dust grains as suggested by Bruce T. Draine and Alex Lazarian in 1998, most likely polycyclic aromatic hydrocarbons. The anomalous emission was first discovered as a by-product of Cosmic Microwave Background observations which make very sensitive measurements of the microwave sky which have to identify and remove contamination from the galaxy. The smallest dust grains are thought to have only hundreds of atoms. History Anomalous microwave emission was first seen as a surprising statistical correlation of microwave sky variations with far infrared (FIR) emission (Kogut et al. 1996, Leitch et al. 1997). This signal traced the warm galactic dust emission which was unexpected as the extrapolated infrared dust signal to microwave frequencies sho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term ''Milky Way'' is a translation of the Latin ', from the Greek ('), meaning "milky circle". From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies. The Milky Way is a barred spiral galaxy with an estimated D25 isophotal diameter of , but only about 1,000 light years thick at the spiral arms (more at the bulg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bruce T
The English language name Bruce arrived in Scotland with the Normans, from the place name Brix, Manche in Normandy, France, meaning "the willowlands". Initially promulgated via the descendants of king Robert the Bruce (1274−1329), it has been a Scottish surname since medieval times; it is now a common given name. The variant ''Lebrix'' and ''Le Brix'' are French variations of the surname. Actors * Bruce Bennett (1906–2007), American actor and athlete * Bruce Boxleitner (born 1950), American actor * Bruce Campbell (born 1958), American actor, director, writer, producer and author * Bruce Davison (born 1946), American actor and director * Bruce Dern (born 1936), American actor * Bruce Gray (1936–2017), American-Canadian actor * Bruce Greenwood (born 1956), Canadian actor and musician * Bruce Herbelin-Earle (born 1998), English-French actor and model * Bruce Jones (born 1953), English actor * Bruce Kirby (1925–2021), American actor * Bruce Lee (1940–1973), martial art ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alex Lazarian
Alexandre Lazarian is an astrophysicist. He is a professor of astronomy at the University of Wisconsin–Madison with a joint appointment at the Department of Physics. He is a fellow of the American Physical Society. Career Lazarian obtained his Diploma in the theoretical physics group led by Vitaly Ginzburg. He received his PhD in 1994 from University of Cambridge under supervision of Martin Rees. After his PhD, Lazarian spent three years as a postdoc in Princeton University and one year as Research Associate at Canadian Institute for Theoretical Astrophysics. Since 1998, he has been working as a professor at the University of Wisconsin–Madison. His research involves MHD Theory, Magnetic Reconnection, Dynamo Theory and Interstellar Dust. Selected publications * * Awards * 2021 Ronald C. Davidson Award for Plasma Physics * 2012 Fellow of American Physical Society, American Physical Society (2012) * 2010 Humbold Research Award, Alexander von Humboldt Foundation The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycyclic Aromatic Hydrocarbons
A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. PAHs are uncharged, non-polar and planar. Many are colorless. Many of them are found in coal and in oil deposits, and are also produced by the combustion of organic matter—for example, in engines and incinerators or when biomass burns in forest fires. Polycyclic aromatic hydrocarbons are discussed as possible starting materials for abiotic syntheses of materials required by the earliest forms of life. Nomenclature and structure The terms polyaromatic hydrocarbon or polynuclear aromatic hydrocarbon are also used for this concept. By definition, polycyclic aromatic hydrocarbons have multiple rings, precluding benzene from being considered a PAH. Some sources, such as the US EPA and CDC, consider naphthalene to be the simplest PAH. Other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Microwave Background
In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space. It is an important source of data on the early universe because it is the oldest electromagnetic radiation in the universe, dating to the epoch of recombination when the first atoms were formed. With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark (see: Olbers' paradox). However, a sufficiently sensitive radio telescope shows a faint background brightness, or glow, almost uniform, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The accidental discovery of the CMB in 1965 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s, and earned th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Background Explorer
The Cosmic Background Explorer (COBE ), also referred to as Explorer 66, was a NASA satellite dedicated to cosmology, which operated from 1989 to 1993. Its goals were to investigate the cosmic microwave background radiation (CMB or CMBR) of the universe and provide measurements that would help shape our understanding of the cosmos. COBE's measurements provided two key pieces of evidence that supported the Big Bang theory of the universe: that the CMB has a near-perfect black-body spectrum, and that it has very faint anisotropies. Two of COBE's principal investigators, George F. Smoot and John C. Mather, received the Nobel Prize in Physics in 2006 for their work on the project. According to the Nobel Prize committee, "the COBE project can also be regarded as the starting point for cosmology as a precision science". COBE was the second cosmic microwave background satellite, following RELIKT-1, and was followed by two more advanced spacecraft: the Wilkinson Microwave Anisotropy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DIRBE
Diffuse Infrared Background Experiment (DIRBE) was an experiment on NASA's COBE mission, to survey the diffuse infrared sky. Measurements were made with a reflecting telescope with 19 cm diameter aperture.Riccardo Giacconi, Daniela Calzetti, Mario Livio, Piero Madau Space Telescope Science Institute (U.S.) - Extragalactic background radiation: a meeting in honor of Riccardo Giacconi : proceedings of the Extragalactic Background Radiation Meeting, Baltimore, 1993 May 18-20, Volume 1993 - Page 137 (Google Books accessed October 2010)/ref> The goal was to obtain brightness maps of the universe at ten frequency bands ranging from the near to far infrared (1.25 to 240 micrometer). Also, linear polarization was measured at 1.25, 2.2, and 3.5 micrometers. During the mission, the instrument could sample half the celestial sphere each day. Mission details The Cosmic Background Explorer (COBE) mission was launched in November 1989. The spacecraft contained liquid helium that cooled ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Owens Valley Radio Observatory
Owens Valley Radio Observatory (OVRO) is a radio astronomy observatory located near Big Pine, California (US) in Owens Valley. It lies east of the Sierra Nevada, approximately north of Los Angeles and southeast of Bishop. It was established in 1956, and is owned and operated by the California Institute of Technology (Caltech). The Owens Valley Solar Array portion of the observatory has been operated by New Jersey Institute of Technology (NJIT) since 1997. One of the ten dish-antenna radiotelescope systems of the Very Long Baseline Array is located on a sublease within the Owens Valley observatory. About The Owens Valley Radio Observatory (OVRO), one of the largest university-operated radio observatories in the world, has its origins in the late 1940s with three individuals: Lee DuBridge, president of California Institute of Technology (Caltech); Robert Bacher, chairman of the Division of Physics, Mathematics and Astronomy; and Jesse Greenstein, professor of astrophysics. In 1954, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IRAS
The Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten months. The telescope was a joint project of the United States (NASA), the Netherlands ( NIVR), and the United Kingdom ( SERC). Over 250,000 infrared sources were observed at 12, 25, 60, and 100 micrometer wavelengths. Support for the processing and analysis of data from IRAS was contributed from the Infrared Processing and Analysis Center at the California Institute of Technology. Currently, the Infrared Science Archive at IPAC holds the IRAS archive. The success of IRAS led to interest in the 1985 Infrared Telescope (IRT) mission on the Space Shuttle, and the planned Shuttle Infrared Telescope Facility which eventually transformed into the Space Infrared Telescope Facility, SIRTF, which in turn was developed into the Spitzer Space ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bremsstrahlung
''Bremsstrahlung'' (), from "to brake" and "radiation"; i.e., "braking radiation" or "deceleration radiation", is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typically an electron by an atomic nucleus. The moving particle loses kinetic energy, which is converted into radiation (i.e., photons), thus satisfying the law of conservation of energy. The term is also used to refer to the process of producing the radiation. ''Bremsstrahlung'' has a continuous spectrum, which becomes more intense and whose peak intensity shifts toward higher frequencies as the change of the energy of the decelerated particles increases. Broadly speaking, ''bremsstrahlung'' or braking radiation is any radiation produced due to the deceleration (negative acceleration) of a charged particle, which includes synchrotron radiation (i.e., photon emission by a relativistic particle), cyclotron radiation (i.e. photon emission by a non ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Dipole Moment
The electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. The SI unit for electric dipole moment is the coulomb-meter (C⋅m). The debye (D) is another unit of measurement used in atomic physics and chemistry. Theoretically, an electric dipole is defined by the first-order term of the multipole expansion; it consists of two equal and opposite charges that are infinitesimally close together, although real dipoles have separated charge.Many theorists predict elementary particles can have very tiny electric dipole moments, possibly without separated charge. Such large dipoles make no difference to everyday physics, and have not yet been observed. (See electron electric dipole moment). However, when making measurements at a distance much larger than the charge separation, the dipole gives a good approximation of the actual electric field. The dipole is represented by a v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Larmor Formula
In electrodynamics, the Larmor formula is used to calculate the total power radiated by a nonrelativistic point charge as it accelerates. It was first derived by J. J. Larmor in 1897, in the context of the wave theory of light. When any charged particle (such as an electron, a proton, or an ion) accelerates, energy is radiated in the form of electromagnetic waves. For a particle whose velocity is small relative to the speed of light (i.e., nonrelativistic), the total power that the particle radiates (when considered as a point charge) can be calculated by the Larmor formula: P = \frac \left(\frac\right)^2 = \frac= \frac = \mu_0 \frac \text P = \frac \text where \dot v or a — is the proper acceleration, q — is the charge, and c — is the speed of light. A relativistic generalization is given by the Liénard–Wiechert potentials. In either unit system, the power radiated by a single electron can be expressed in terms of the classical electron radius and electr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
