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Gary Ferland
Gary Joseph Ferland (born May 10, 1951, in Washington D.C.) is an American astrophysicist. He is a professor of Physics and Astronomy at The University of Kentucky. He joined the University of TexasAstronomy Departmentin 1973 where he received hiPh.D.in 1978, studying the 1975 explosion of V1500 Cygni at McDonald Observatory. From 1978 to 1980 he was at the Institute of Astronomy, Cambridge where he worked with Martin Rees on International Ultraviolet Explorer observations of radio galaxies He joined the faculty of the University of Kentucky in 1980. The American Astronomical Society's Astronomy Genealogy Project lists the 17 PhDs he has supervised. Ferland is a Fellow of the American Astronomical Society, and has served on their Governing Council in addition to their Publications Board. He was named Fellow of the American Association for the Advancement of Science in 2023 and is a Fellow of the Royal Astronomical Society. He is a long-time member of the Internationa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Washington D
Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered on Washington, D.C. * George Washington (1732–1799), the first president of the United States Washington may also refer to: Places England * Washington, Tyne and Wear, a town in the City of Sunderland metropolitan borough ** Washington Old Hall, ancestral home of the family of George Washington * Washington, West Sussex, a village and civil parish Greenland * Cape Washington, Greenland * Washington Land Philippines *New Washington, Aklan, a municipality *Washington, a barangay in Catarman, Northern Samar *Washington, a barangay in Escalante, Negros Occidental *Washington, a barangay in San Jacinto, Masbate *Washington, a barangay in Surigao City United States * Washington, Wisconsin (other) * Fort Washington (disambiguatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interstellar Medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space. The energy that occupies the same volume, in the form of electromagnetic radiation, is the interstellar radiation field. The interstellar medium is composed of multiple phases distinguished by whether matter is ionic, atomic, or molecular, and the temperature and density of the matter. The interstellar medium is composed, primarily, of hydrogen, followed by helium with trace amounts of carbon, oxygen, and nitrogen. The thermal pressures of these phases are in rough equilibrium with one another. Magnetic fields and turbulent motions also provide pressure in the ISM, and are typically more important, dynamically, than the thermal pressure is. In the interstellar medium, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Program
A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components. A computer program in its human-readable form is called source code. Source code needs another computer program to execute because computers can only execute their native machine instructions. Therefore, source code may be translated to machine instructions using the language's compiler. ( Assembly language programs are translated using an assembler.) The resulting file is called an executable. Alternatively, source code may execute within the language's interpreter. If the executable is requested for execution, then the operating system loads it into memory and starts a process. The central processing unit will soon switch to this process so it can fetch, decode, and then execute each machine instruction. If the source code is requested for execution, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Simulation
Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be determined by comparing their results to the real-world outcomes they aim to predict. Computer simulations have become a useful tool for the mathematical modeling of many natural systems in physics (computational physics), astrophysics, climatology, chemistry, biology and manufacturing, as well as human systems in economics, psychology, social science, health care and engineering. Simulation of a system is represented as the running of the system's model. It can be used to explore and gain new insights into new technology and to estimate the performance of systems too complex for analytical solutions. Computer simulations are realized by running computer programs that can be either small, running almost instantly on small devices, or large ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectroscopy
Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter waves and acoustic waves can also be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO) In simpler terms, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of astronomy, chemistry, materials science, and physics, allowing the composition, physical structure and e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Open Access
Open access (OA) is a set of principles and a range of practices through which research outputs are distributed online, free of access charges or other barriers. With open access strictly defined (according to the 2001 definition), or libre open access, barriers to copying or reuse are also reduced or removed by applying an open license for copyright. The main focus of the open access movement is "peer reviewed research literature". Historically, this has centered mainly on print-based academic journals. Whereas non-open access journals cover publishing costs through access tolls such as subscriptions, site licenses or pay-per-view charges, open-access journals are characterised by funding models which do not require the reader to pay to read the journal's contents, relying instead on author fees or on public funding, subsidies and sponsorships. Open access can be applied to all forms of published research output, including peer-reviewed and non peer-reviewed academic journa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science News
''Science News (SN)'' is an American bi-weekly magazine devoted to articles about new scientific and technical developments, typically gleaned from recent scientific and technical journals. History ''Science News'' has been published since 1922 by Society for Science & the Public, a non-profit organization founded by E. W. Scripps in 1920. American chemist Edwin Slosson served as the publication's first editor. From 1922 to 1966, it was called ''Science News Letter''. The title was changed to ''Science News'' with the March 12, 1966 issue (vol. 89, no. 11). Tom Siegfried was the editor from 2007 to 2012. In 2012, Siegfried stepped down, and Eva Emerson became the Editor in Chief of the magazine. In 2017, Eva Emerson stepped down to become the editor of a new digital magazine, Annual Reviews. On February 1, 2018 Nancy Shute became the Editor in Chief of the magazine. In April 2008, the magazine changed from a weekly format to the current biweekly format, and the website was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 5548
NGC 5548 is a Type I Seyfert galaxy with a bright, active nucleus. This activity is caused by matter flowing onto a 65 million solar mass () supermassive black hole at the core. Morphologically, this is an unbarred lenticular galaxy with tightly-wound spiral arms, while shell and tidal tail features suggest that it has undergone a cosmologically-recent merger or interaction event. NGC 5548 is approximately 245 million light years away and appears in the constellation Boötes. The apparent visual magnitude of NGC 5548 is approximately 13.3 in the V band. In 1943, this galaxy was one of twelve nebulae listed by American astronomer Carl Keenan Seyfert that showed broad emission lines in their nuclei. Members of this class of objects became known as Seyfert galaxies, and they were noted to have a higher than normal surface brightness in their nuclei. Observation of NGC 5548 during the 1960s with radio telescopes showed an enhanced level of radio emission. Spectrograms of the nucleus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seyfert Galaxy
Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars. They have quasar-like nuclei (very luminous, distant and bright sources of electromagnetic radiation) with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, their host galaxies are clearly detectable. Seyfert galaxies account for about 10% of all galaxies and are some of the most intensely studied objects in astronomy, as they are thought to be powered by the same phenomena that occur in quasars, although they are closer and less luminous than quasars. These galaxies have supermassive black holes at their centers which are surrounded by accretion discs of in-falling material. The accretion discs are believed to be the source of the observed ultraviolet radiation. Ultraviolet emission and absorption lines provide the best diagnostics for the composition of the surrounding material. Seen in visible light, most Seyfert galaxies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tidal Disruption Event
A tidal disruption event (TDE) is an astronomical phenomenon that occurs when a star approaches sufficiently close to a supermassive black hole (SMBH) to be pulled apart by the black hole's tidal force, experiencing spaghettification. A portion of the star's mass can be captured into an accretion disk around the black hole (if the star is on a parabolic orbit), resulting in a temporary flare of electromagnetic radiation as matter in the disk is consumed by the black hole. According to early papers, tidal disruption events should be an inevitable consequence of massive black holes' activity hidden in galaxy nuclei, whereas later theorists concluded that the resulting explosion or flare of radiation from the accretion of the stellar debris could be a unique signpost for the presence of a dormant black hole in the center of a normal galaxy. Sometimes a star can survive the encounter with an SMBH, and a remnant is formed. These events are termed partial TDEs. History Physicist Joh ... [...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] |
Photodissociation Region
In astrophysics, photodissociation regions (or photon-dominated regions, PDRs) are predominantly neutral regions of the interstellar medium in which far ultraviolet photons strongly influence the gas chemistry and act as the most important source of heat. They occur in any region of interstellar gas that is dense and cold enough to remain neutral, but that has too low a column density to prevent the penetration of far-UV photons from distant, massive stars. A typical and well-studied example is the gas at the boundary of a giant molecular cloud. PDRs are also associated with HII regions, reflection nebulae, active galactic nuclei, and Planetary nebulae. All the atomic gas and most of the molecular gas in the galaxy is found in PDRs. History The study of photodissociation regions began from early observations of the star-forming regions Orion A and M17 which showed neutral areas bright in infrared radiation lying outside ionised HII regions An H II region or HII regio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
