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Neutron Star Collision
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] |
Radioactive Decay
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered ''radioactive''. Three of the most common types of decay are Alpha decay, alpha, Beta decay, beta, and Gamma ray, gamma decay. The weak force is the Fundamental interactions, mechanism that is responsible for beta decay, while the other two are governed by the electromagnetic force, electromagnetic and nuclear forces. Radioactive decay is a randomness, random process at the level of single atoms. According to quantum mechanics, quantum theory, it is impossible to predict when a particular atom will decay, regardless of how long the atom has existed. However, for a significant number of identical atoms, the overall decay rate can be expressed as a decay constant or as a half-life. The half-lives of radioactive atoms have a huge range: f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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] |
GRB 170817A
GW170817 was a gravitational wave (GW) observed by the LIGO and 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 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''. GW170817 had an audible duration of approximately 100 seconds and exhibited the characteristic intensity and f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomy (magazine)
''Astronomy'' is a monthly American magazine about astronomy. Targeting amateur astronomers, it contains columns on sky viewing, reader-submitted astrophotographs, and articles on astronomy and astrophysics for general readers. History ''Astronomy'' is a magazine about the science and hobby of astronomy. Based near Milwaukee in Brookfield, Wisconsin, it was produced by Kalmbach Publishing. ''Astronomy''’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general. ''Astronomy'' was founded in 1973 by Stephen A. Walther, a graduate of the University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydra (constellation)
Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees, and also the longest at over 100 degrees. Its southern end borders Libra (constellation), Libra and Centaurus (constellation), Centaurus and its northern end borders Cancer (constellation), Cancer. It was included among the 48 constellations listed by the 2nd century astronomer Ptolemy. Commonly represented as a water snake (other), water snake, it straddles the celestial equator. History and mythology Western mythology The Greek constellation of Hydra is an adaptation of a Babylonian astronomy, Babylonian constellation: the MUL.APIN includes a "serpent" constellation (MUL.DINGIR.MUŠ) that loosely corresponds to Hydra. It is one of two Babylonian "serpent" constellations (the other being the origin of the Greek Serpens), a mythological hybrid of serpent, lion and bird. The shape of Hydra resembles a twisting snake, and features as such in some Greek myths. One myth associates it w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elliptical Galaxy
An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the three main galaxy morphological classification, classes of galaxy described by Edwin Hubble in his Hubble sequence#Physical significance, Hubble sequence and 1936 work ''The Realm of the Nebulae'', with their intermediate scale disks, a subset of the "early-type" galaxy population. Most elliptical galaxies are composed of older, stellar evolution#Low-mass stars, low-mass stars, with a sparse interstellar medium, and they tend to be surrounded by large numbers of globular clusters. Star formation activity in elliptical galaxies is typically minimal; they may, however, undergo brief periods of star formation when merging with other galaxies. Elliptical galaxies are believed to make up approximately 10–15% of galaxies in the Virgo Supercluster, and they are not the dominant type of galaxy in the universe overall. They are preferentially fou ... [...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] |
Gravitational Wave
Gravitational waves are oscillations of the gravitational field that Wave propagation, travel through space at the speed of light; they are generated by the relative motion of gravity, gravitating masses. They were proposed by Oliver Heaviside in 1893 and then later by Henri Poincaré in 1905 as the gravitational equivalent of Electromagnetic radiation, electromagnetic waves. In 1916, Albert Einstein demonstrated that gravitational waves result from his general theory of relativity as ripples in spacetime. 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, instead asserting that gravity has instantaneous effect everywhere. Gravitational waves therefore stand as an important relativistic phenomenon that is absent from Newtonian physics. Gravitational-wave astronomy has the advantage that, unlike elec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LIGO Scientific Collaboration
The LIGO Scientific Collaboration (LSC) is a scientific collaboration of international physics institutes and research groups dedicated to the search for gravitational waves. History The LSC was established in 1997, under the leadership of Barry Barish. Its mission is to ensure equal scientific opportunity for individual participants and institutions by organizing research, publications, and all other scientific activities, and it includes scientists from both LIGO Laboratory and collaborating institutions. Barish appointed Rainer Weiss as the first spokesperson. LSC members have access to the US-based Advanced LIGO detectors in Hanford, Washington and in Livingston, Louisiana, as well as the GEO 600 detector in Sarstedt, Germany. Under an agreement with the European Gravitational Observatory (EGO), LSC members also have access to data from the Virgo detector in Pisa, Italy. While the LSC and the Virgo Collaboration are separate organizations, they cooperate closely and ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virgo Interferometer
The Virgo interferometer is a large-scale scientific instrument near Pisa, Italy, for detecting gravitational waves. The detector is a Michelson interferometer, which can detect the minuscule length variations in its two arms induced by the passage of gravitational waves. The required precision is achieved using many systems to isolate it from the outside world, including keeping its mirrors and instrumentation in an ultra-high vacuum and suspending them using complex systems of Pendulum, pendula. Between its periodic observations, the detector is upgraded to increase its sensitivity. The observation runs are performed in collaboration with other similar detectors, including the two Laser Interferometer Gravitational-Wave Observatories (LIGO) in the United States and the Japanese Kamioka Gravitational Wave Detector (KAGRA), because cooperation between several detectors is crucial for detecting gravitational waves and pinpointing their origin. Virgo was conceived and built whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LIGO
The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Prior to LIGO, all data about the universe has come in the form of light and other forms of electromagnetic radiation, from limited direct exploration on relatively nearby Solar System objects such as the Moon, Mars, Venus, Jupiter and their moons, asteroids etc, and from high energy cosmic particles. Initially, two large observatories were built in the United States with the aim of detecting gravitational waves by laser interferometry. Two additional, smaller gravity wave observatories are now operational in Japan KAGRA, (KAGRA) and Italy Virgo interferometer, (Virgo). The two LIGO observatories use mirrors spaced four kilometers apart to measure changes in length—over an effective span of 1120 km—of less than one ten-thousandth the charge radius, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
