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SSS17a
GW170817 was a gravitational wave (GW) observed by the LIGO and Virgo interferometer, Virgo detectors on 17 August 2017, originating within the shell elliptical galaxy NGC 4993, about 144 million light years away. The wave was produced by the last moments of the inspiral of a binary pair of neutron stars, ending with their Neutron star merger, merger. , it is the only GW detection to be definitively correlated with any electromagnetic observation. Unlike the five prior GW detections—which were of merging black holes and thus not expected to have detectable electromagnetic signals—the aftermath of this merger was seen across the electromagnetic spectrum by 70 observatories on 7 continents and in space, marking a significant breakthrough for multi-messenger astronomy. The discovery and subsequent observations of GW170817 were given the Breakthrough of the Year award for 2017 by the journal Science (journal), ''Science''. GW170817 had an audible duration of approximately 100&n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Star Merger
A neutron star merger is the stellar collision of neutron stars. When two neutron stars fall into mutual orbit, they gradually inspiral, spiral inward due to the loss of energy emitted as gravitational radiation. When they finally meet, their merger leads to the formation of either a more massive neutron star, or—if the mass of the remnant exceeds the Tolman–Oppenheimer–Volkoff limit—a black hole. The merger can create a magnetic field that is trillions of times stronger than that of Earth in a matter of one or two milliseconds. The immediate event creates a gamma-ray burst#Short gamma-ray bursts, short gamma-ray burst visible over hundreds of millions, or even billions of light years. The merger of neutron stars momentarily creates an environment of such extreme neutron flux that the r-process, ''r''-process can occur. This reaction accounts for the nucleosynthesis of around half of the isotopes in elements heavier than iron. The mergers also produce kilonovae, which ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multi-messenger Astronomy
Multi-messenger astronomy is the coordinated observation and interpretation of multiple signals received from the same astronomical event. Many types of cosmological events involve complex interactions between a variety of astrophysical processes, each of which may independently emit signals of a characteristic "messenger" type: electromagnetic radiation (including infrared, visible light and X-rays), gravitational waves, neutrinos, and cosmic rays. When received on Earth, identifying that disparate observations were generated by the same source can allow for improved reconstruction or a better understanding of the event, and reveals more information about the source. The main multi-messenger sources outside the heliosphere are: compact binary pairs ( black holes and neutron stars), supernovae, irregular neutron stars, gamma-ray bursts, active galactic nuclei, and relativistic jets. The table below lists several types of events and expected messengers. Detection from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NGC 4993
NGC 4993 (also catalogued as NGC 4994 in the New General Catalogue) is a lenticular galaxy located about 140 million light-years away in the constellation Hydra (constellation), Hydra. It was discovered on 26 March 1789 by William Herschel and is a member of the NGC 4993 Group. NGC 4993 was the site of GW170817, a neutron star merger, collision of two neutron stars, the first astronomical event detected in both electromagnetic and gravitational radiation, a discovery given the Breakthrough of the Year award for 2017 by the journal Science (journal), ''Science''. Detecting a gravitational wave event associated with the gamma-ray burst provided direct confirmation that binary neutron star collisions produce short gamma-ray bursts. Physical characteristics NGC 4993 has several concentric shells of stars and a large dust lane—with a diameter of approximately a few kiloparsecs—which surrounds the nucleus and is stretched out into an "s" shape. The dust lane appears to be connec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
J2000
In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodies) can be used to generate an ephemeris, a table of values giving ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
INTEGRAL
In mathematics, an integral is the continuous analog of a Summation, sum, which is used to calculate area, areas, volume, volumes, and their generalizations. Integration, the process of computing an integral, is one of the two fundamental operations of calculus,Integral calculus is a very well established mathematical discipline for which there are many sources. See and , for example. the other being Derivative, differentiation. Integration was initially used to solve problems in mathematics and physics, such as finding the area under a curve, or determining displacement from velocity. Usage of integration expanded to a wide variety of scientific fields thereafter. A definite integral computes the signed area of the region in the plane that is bounded by the Graph of a function, graph of a given Function (mathematics), function between two points in the real line. Conventionally, areas above the horizontal Coordinate axis, axis of the plane are positive while areas below are n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Transient
Time-domain astronomy is the study of how astronomical objects change with time. Said to have begun with Galileo's '' Letters on Sunspots'', the field has now naturally expanded to encompass variable objects beyond the Solar System. Temporal variation may originate from movement of the source, or changes in the object itself. Common targets include novae, supernovae, pulsating stars, flare stars, blazars and active galactic nuclei. Optical time domain surveys include OGLE, HAT-South, PanSTARRS, SkyMapper, ASAS, WASP, CRTS, GOTO, and the forthcoming LSST at the Vera C. Rubin Observatory. Time-domain astronomy studies transient astronomical events ("''transients''"), which include various types of variable stars, including periodic, quasi-periodic, high proper motion stars, and lifecycle events (supernovae, kilonovae) or other changes in behavior or type. Non-stellar transients include asteroids, planetary transits and comets. Transients characterize astronomical o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kilonova
A kilonova (also called a macronova) is a transient astronomical event that occurs in a compact star, compact binary system when two neutron stars (BNS) or a neutron star and a black hole collide. The kilonova, visible over the weeks and months following the merger, is an isotropically expanding luminous afterglow of electromagnetic radiation emitted by the radioactive decay of r-process, ''r''-process nuclei synthesized by—and then ejected from—the initial cataclysmic event. The high sphericity of kilonovae through its early epochs was deduced from the blackbody nature of the spectrum observed for the most important recorded neutron star merger, BNS merger, GW170817, GW170817/AT2017gfo. History The existence of thermal transient events from neutron star mergers was first introduced by Li & Bohdan Paczyński, Paczyński in 1998. The radioactive glow arising from the merger ejecta was originally called mini-supernova, as it is to the brightness of a typical supernova, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David Reitze
David Howard Reitze (born 6 January 1961) is an American laser physicist who is professor of physics at the University of Florida and served as the scientific spokesman of the Laser Interferometer Gravitational-Wave Observatory ( LIGO) experiment in 2007-2011. In August 2011, he took a leave of absence from the University of Florida to be the Executive Director of LIGO, stationed at the California Institute of Technology, Pasadena, California. He obtained his BA in 1983 from Northwestern University, his PhD in physics from the University of Texas at Austin in 1990, and had positions at Bell Communications Research and Lawrence Livermore National Laboratory, before taking his faculty position at the University of Florida. He is a Fellow of the American Physical Society, the Optical Society, and the American Association for the Advancement of Science. An expert in ultrafast optics and laser spectroscopy, he now specialises in laser-based interferometric gravitational wave det ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Press Club (United States)
The National Press Club is a Professional association, professional organization and social community in Washington, D.C. for journalists and communications professionals. It hosts public and private gatherings with invited speakers from public life. The club also offers event space to outside groups to host business meetings, news conferences, industry gatherings, and social events. It was founded in 1908. The club has been visited by most Presidents of the United States, U.S. presidents; since Warren Harding, many have also been members and spoken from the club's podium. Others who have appeared at the club include monarchs, prime ministers, premiers, members of United States Congress, Congress, Cabinet of the United States, Cabinet officials, ambassadors, scholars, entertainers, business leaders, and athletes. The club's emblem is the owl, in deference to wisdom, awareness and nights spent working. History Founding On March 12, 1908, 32 newspapermen met at the Washington Cha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Short Gamma-ray Burst
In gamma-ray astronomy, gamma-ray bursts (GRBs) are extremely energetic events occurring in distant Galaxy, galaxies which represent the brightest and most powerful class of explosion in the universe. These extreme Electromagnetic radiation, electromagnetic emissions are second only to the Big Bang as the most energetic and luminous phenomenon ever known. Gamma-ray bursts can last from a few milliseconds to several hours. After the initial flash of gamma rays, a longer-lived afterglow is emitted, usually in the longer wavelengths of X-ray, ultraviolet, visible spectrum, optical, infrared, microwave or radio waves, radio frequencies. 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. Short-duration (sGRB) events are a subclass of GRB signals that are now known to originate from the cataclysmic Neutron star merger, merger of binary neutron stars. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
European Southern Observatory
The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 member states for ground-based astronomy. Created in 1962, ESO has provided astronomers with state-of-the-art research facilities and access to the southern sky. The organisation employs over 750 staff members and receives annual member state contributions of approximately €162 million. Its observatories are located in northern Chile. ESO has built and operated some of the largest and most technologically advanced telescopes. These include the 3.6 m New Technology Telescope, an early pioneer in the use of active optics, and the Very Large Telescope (VLT), which consists of four individual 8.2 m telescopes and four smaller auxiliary telescopes which can all work together or separately. The Atacama Large Millimeter Array observes the u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
