|
Steven Detweiler
Steven L. Detweiler was a theoretical physicist and professor of physics at the University of Florida best known for proposing pulsar timing arrays as a means to detect gravitational waves, an idea that led to the discovery of a stochastic gravitational wave background in 2023. __TOC__ Background Detweiler received his bachelor's degree from Princeton University in 1969 and his Ph.D. from the University of Chicago in 1976 under the supervision of James R. Ipser. In 2013, he was elected to a fellowship of the American Physical Society in recognition of ''his many and varied contributions to gravitational physics''. Detweiler's research focused on the dynamics of stars and black holes, as well as on the production and observation of gravitational waves. In 1975 together with Subrahmanyan Chandrasekhar, Detweiler calculated the effects of fluctuations on black holes. This is important for understanding the stability of black holes, as well as the later stages of the dynamics of bla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yonkers, New York
Yonkers () is a city in Westchester County, New York, United States. Developed along the Hudson River, it is the third most populous city in the state of New York (state), New York, after New York City and Buffalo, New York, Buffalo. The population of Yonkers was 211,569 as enumerated in the 2020 United States Census. It is classified as an inner suburb of New York City, located directly to the north of the Bronx and approximately two miles (3 km) north of Marble Hill, Manhattan, the northernmost point in Manhattan. Yonkers's downtown is centered on a plaza known as Getty Square, where the municipal government is located. The downtown area also houses significant local businesses and nonprofit organizations. It serves as a major retail hub for Yonkers and the northwest Bronx. The city is home to several attractions, including access to the Hudson River, Tibbetts Brook Park, with its public pool with slides and lazy river and two-mile walking loop Untermyer Park; Hudson Ri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitational Waves
Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1893 and then later by Henri Poincaré in 1905 as waves similar to electromagnetic waves but the gravitational equivalent. Gravitational waves were later predicted in 1916 by Albert Einstein on the basis of his general theory of relativity as ripples in spacetime. Later he refused to accept gravitational waves. Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation. Newton's law of universal gravitation, part of classical mechanics, does not provide for their existence, since that law is predicated on the assumption that physical interactions propagate instantaneously (at infinite speed)showing one of the ways the methods of Newtonian physics are unable to explain ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NANOGrav
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is a consortium of astronomers who share a common goal of detecting gravitational waves via regular observations of an ensemble of millisecond pulsars using the Green Bank and Arecibo radio telescopes. This project is being carried out in collaboration with international partners in the Parkes Pulsar Timing Array in Australia and the European Pulsar Timing Array as part of the International Pulsar Timing Array. Gravitational wave detection using pulsar timing Gravitational waves are an important prediction from Einstein's general theory of relativity and result from the bulk motion of matter, fluctuations during the early universe and the dynamics of space-time itself. Pulsars are rapidly rotating, highly magnetized neutron stars formed during the supernova explosions of massive stars. They act as highly accurate clocks with a wealth of physical applications ranging from celestial mechanics, neutron star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysical Journal
''The Astrophysical Journal'', often abbreviated ''ApJ'' (pronounced "ap jay") in references and speech, is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler. The journal discontinued its print edition and became an electronic-only journal in 2015. Since 1953 ''The Astrophysical Journal Supplement Series'' (''ApJS'') has been published in conjunction with ''The Astrophysical Journal'', with generally longer articles to supplement the material in the journal. It publishes six volumes per year, with two 280-page issues per volume. ''The Astrophysical Journal Letters'' (''ApJL''), established in 1967 by Subrahmanyan Chandrasekhar as Part 2 of ''The Astrophysical Journal'', is now a separate journal focusing on the rapid publication of high-impact astronomical research. The three journals were published by the University of Chicago Press for the American Astronomical Society un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Donald C
Donald is a masculine given name derived from the Gaelic name ''Dòmhnall''.. This comes from the Proto-Celtic *''Dumno-ualos'' ("world-ruler" or "world-wielder"). The final -''d'' in ''Donald'' is partly derived from a misinterpretation of the Gaelic pronunciation by English speakers, and partly associated with the spelling of similar-sounding Germanic names, such as ''Ronald''. A short form of ''Donald'' is '' Don''. Pet forms of ''Donald'' include ''Donnie'' and ''Donny''. The feminine given name ''Donella'' is derived from ''Donald''. ''Donald'' has cognates in other Celtic languages: Modern Irish ''Dónal'' (anglicised as ''Donal'' and ''Donall'');. Scottish Gaelic ''Dòmhnall'', ''Domhnull'' and ''Dòmhnull''; Welsh '' Dyfnwal'' and Cumbric ''Dumnagual''. Although the feminine given name '' Donna'' is sometimes used as a feminine form of ''Donald'', the names are not etymologically related. Variations Kings and noblemen Domnall or Domhnall is the name of many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mikhail Sazhin (astrophysicist)
Mikhail Sazhin may refer to: * Mikhail Sazhin (astrophysicist) (born 1951), Russian astrophysicist * Mikhail Sazhin (colonel) (1899–1971), Russian military leader * Mikhail Sazhin (painter) (1818–1885), Russian landscape painter * Mikhail Sazhin (revolutionary) (1845–1934), Russian revolutionary and anarchist {{human name dab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light-years
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 (one million million, or billion in long scale). As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in a vacuum in one Julian year (365.25 days). Because it includes the time-measurement word "year", the term ''light-year'' is sometimes misinterpreted as a unit of time. The ''light-year'' is most often used when expressing distances to stars and other distances on a galactic scale, especially in non-specialist contexts and popular science publications. The unit most commonly used in professional astronomy is the parsec (symbol: pc, about 3.26 light-years) which derives from astrometry; it is the distance at which one astronomical unit subtends an angle of one second of arc. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subrahmanyan Chandrasekhar
Subrahmanyan Chandrasekhar (; ) (19 October 1910 – 21 August 1995) was an Indian-American theoretical physicist who spent his professional life in the United States. He shared the 1983 Nobel Prize for Physics with William A. Fowler for "...theoretical studies of the physical processes of importance to the structure and evolution of the stars". His mathematical treatment of stellar evolution yielded many of the current theoretical models of the later evolutionary stages of massive stars and black holes. Many concepts, institutions, and inventions, including the Chandrasekhar limit and the Chandra X-Ray Observatory, are named after him. Chandrasekhar worked on a wide variety of problems in physics during his lifetime, contributing to the contemporary understanding of stellar structure, white dwarfs, stellar dynamics, stochastic process, radiative transfer, the quantum theory of the hydrogen anion, hydrodynamic and hydromagnetic stability, turbulence, equilibrium and the st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Holes
A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. Although it has a great effect on the fate and circumstances of an object crossing it, it has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly. Objects whose gravitational fields are too strong for light to escape were first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Physical Society
The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of knowledge of physics. The society publishes more than a dozen scientific journals, including the prestigious ''Physical Review'' and '' Physical Review Letters'', and organizes more than twenty science meetings each year. APS is a member society of the American Institute of Physics. Since January 2021 the organization has been led by chief executive officer Jonathan Bagger. History The American Physical Society was founded on May 20, 1899, when thirty-six physicists gathered at Columbia University for that purpose. They proclaimed the mission of the new Society to be "to advance and diffuse the knowledge of physics", and in one way or another the APS has been at that task ever since. In the early years, virtually the sole activity of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitational Wave Background
The gravitational wave background (also GWB and stochastic background) is a random gravitational-wave signal potentially detectable by gravitational wave detection experiments. Since the background is supposed to be statistically random, it has yet been researched only in terms of such statistical descriptors as the mean, the variance, etc. Sources of a stochastic background Several potential sources for the background are hypothesized across various frequency bands of interest, with each source producing a background with different statistical properties. The sources of the stochastic background can be broadly divided into two categories: cosmological sources, and astrophysical sources. Cosmological sources Cosmological backgrounds may arise from several early universe sources. Some examples of these sources include time-varying scalar (classical) fields in the early universe, "preheating" mechanisms after inflation involving energy transfer from inflaton particles to reg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulsar Timing Array
A pulsar timing array (PTA) is a set of pulsars which is analysed to search for correlated signatures in the pulse arrival times. There are many applications for pulsar timing arrays. The best known is the use of an array of millisecond pulsars to detect and analyse gravitational waves. Such a detection would result from a detailed investigation of the correlation between arrival times of pulses emitted by the millisecond pulsars as a function of the pulsars' angular separations. Overview Millisecond pulsars are used because they are not prone to the starquakes and accretion events which can affect the period of classical pulsars. One influence on these propagation properties are low-frequency gravitational waves, with a frequency of 10−9 to 10−6 hertz; the expected astrophysical sources of such gravitational waves are massive black hole binaries in the centres of merging galaxies, where tens of millions of solar masses are in orbit with a period between months and a few years ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
