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Charles T. Kowal
Charles Thomas Kowal (November 8, 1940 – November 28, 2011) was an American astronomer known for his observations and discoveries in the Solar System. As a staff astronomer at Caltech's Mount Wilson and Palomar Mountain observatories between 1961 and 1984, he found the first of a new class of Solar System objects, the centaurs, discovered two moons of the planet Jupiter, and discovered or co-discovered a number of asteroids, comets and supernovae. He was awarded the James Craig Watson Medal for his contributions to astronomy in 1979. Research In the 1960s, Kowal observed with the Palomar 48" Schmidt telescope, contributing observations to noted cosmologist Fritz Zwicky's six-volume ''Catalogue of Galaxies and of Clusters of Galaxies''. Kowal also began to search for Type Ia supernovae in other galaxies, in an effort led by Zwicky to calibrate the magnitudes of these exploding stars so that they could be used as standard candles, reliable measures of the distance of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buffalo, New York
Buffalo is the second-largest city in the U.S. state of New York (behind only New York City) and the seat of Erie County. It is at the eastern end of Lake Erie, at the head of the Niagara River, and is across the Canadian border from Southern Ontario. With a population of 278,349 according to the 2020 census, Buffalo is the 78th-largest city in the United States. The city and nearby Niagara Falls together make up the two-county Buffalo–Niagara Falls Metropolitan Statistical Area (MSA), which had an estimated population of 1.1 million in 2020, making it the 49th largest MSA in the United States. Buffalo is in Western New York, which is the largest population and economic center between Boston and Cleveland. Before the 17th century, the region was inhabited by nomadic Paleo-Indians who were succeeded by the Neutral, Erie, and Iroquois nations. In the early 17th century, the French began to explore the region. In the 18th century, Iroquois land surrounding Buffalo Creek ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of solar radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles. The coma may be up to 15 times Earth's diameter, while the tail may stretch beyond one astronomical unit. If sufficiently bright, a comet may be seen from Earth without the aid of a telescope and may subtend an arc of 30° (60 Moons) across the sky. Comets have been observed and recorded since ancient times by many cultures and religions. Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several mill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planet-Crossing Asteroid Survey
The Palomar Planet-Crossing Asteroid Survey (PCAS) was an astronomical survey, initiated by American astronomers Eleanor Helin and Eugene Shoemaker at the U.S Palomar Observatory, California, in 1973. The program is responsible for the discovery of 95 near-Earth Objects including 17 comets, while the Minor Planet Center directly credits PCAS with the discovery of 20 numbered minor planets during 1993–1994. PCAS ran for nearly 25 years until June 1995. It had an international extension, INAS, and was the immediate predecessor of the outstandingly successful NEAT program. Notable discoveries The first NEO discovered by PACS was (5496) 1973 NA, an Apollo asteroid with an exceptional orbital inclination of 68 °, the most highly inclined minor planet known until 1999. In 1976, Eleanor Helin discovered 2062 Aten, the first of a new class of asteroids called the Aten asteroids with small orbits that are never far from Earth's orbit. As a result, these objects have a particularly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Near-Earth Asteroid
A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). If a NEO's orbit crosses the Earth's orbit, and the object is larger than across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but a small fraction are comets. There are over 30,503 known near-Earth asteroids (NEAs) and over a hundred known short-period near-Earth comets (NECs). A number of solar-orbiting meteoroids were large enough to be tracked in space before striking the Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of the Earth. Asteroids as small as in diameter can cause significant damage to the local environment and human populations. Larger asteroids penetrate the atmosphere to the surf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Shoemaker
Eugene Merle Shoemaker (April 28, 1928 – July 18, 1997) was an American geologist. He co-discovered Comet Shoemaker–Levy 9 with his wife Carolyn S. Shoemaker and David H. Levy. This comet hit Jupiter in July 1994: the impact was televised around the world. Shoemaker also studied terrestrial craters, such as Barringer Meteor Crater in Arizona, and along with Edward Chao provided the first conclusive evidence of its origin as an impact crater. He was also the first director of the United States Geological Survey's Astrogeology Research Program. He was killed in a car accident while visiting an impact crater site in Australia. After his death, some of his ashes were carried to the Moon with the Lunar Prospector mission. Early life and formal education Shoemaker was born in Los Angeles, California, the son of Muriel May (née Scott), a teacher; and George Estel Shoemaker, who worked in farming, business, teaching, and motion pictures. His parents were natives of Nebraska. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eleanor Helin
Eleanor Francis "Glo" Helin (née Francis, 19 November 1932 – 25 January 2009) was an American astronomer. She was principal investigator of the Near-Earth Asteroid Tracking (NEAT) program of NASA's Jet Propulsion Laboratory. (Some sources give her name as Eleanor Kay Helin.) Helin was a prolific discoverer of minor planets ''(see list)'' and several comets, including periodic comets 111P/Helin–Roman–Crockett, 117P/Helin–Roman–Alu and 132P/Helin–Roman–Alu. She is credited as the discoverer of the object now known as both asteroid 4015 Wilson–Harrington and comet 107P/Wilson–Harrington. Although Wilson and Harrington preceded her by some decades, their observations did not establish an orbit for the object, while her rediscovery did. Helin discovered or co-discovered 903 asteroids and several comets. Biography Helin was born an only child to Fred and Kay Francis. At the age of five, she became ill with polio, which caused her to be bed-ridden for several ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SN 1972e
SN1972E was a supernova in the galaxy NGC 5253 that was discovered 13 May 1972 with an apparent B magnitude of about 8.5, shortly after it had reached its maximum brightness. In terms of apparent brightness, it was the second-brightest supernova of any kind (fainter only than SN 1987A) of the 20th century. It was observed for nearly 700 days, and it became the prototype object for the development of theoretical understanding of Type Ia supernovae. Background The supernova was discovered by Charles Kowal, about 56 arc seconds west and 85 arc seconds south of the center of NGC 5253. The position in the periphery of the galaxy aided observation, minimizing interference by background objects. Well-positioned for Southern Hemisphere observers, it was quite observable from Northern Hemisphere observatories as well. Attempts made to observe it in X-rays with Uhuru and OSO 7 and to detect gamma rays from it via Cherenkov radiation showers gave at best equivocal results. Photomet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Expansion Of The Universe
The expansion of the universe is the increase in distance between any two given gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion whereby the scale of space itself changes. The universe does not expand "into" anything and does not require space to exist "outside" it. This expansion involves neither space nor objects in space "moving" in a traditional sense, but rather it is the metric (which governs the size and geometry of spacetime itself) that changes in scale. As the spatial part of the universe's spacetime metric increases in scale, objects become more distant from one another at ever-increasing speeds. To any observer in the universe, it appears that all of space is expanding, and that all but the nearest galaxies (which are bound by gravity) recede at speeds that are proportional to their distance from the observer. While objects within space cannot travel faster than light, this limitation does not apply to the effects of ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Candle
The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A ''direct'' distance measurement of an astronomical object is possible only for those objects that are "close enough" (within about a thousand parsecs) to Earth. The techniques for determining distances to more distant objects are all based on various measured correlations between methods that work at close distances and methods that work at larger distances. Several methods rely on a standard candle, which is an astronomical object that has a known luminosity. The ladder analogy arises because no single technique can measure distances at all ranges encountered in astronomy. Instead, one method can be used to measure nearby distances, a second can be used to measure nearby to intermediate distances, and so on. Each rung of the ladder provides information that can be used to determine the distances at the next ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Ia Supernova
A Type Ia supernova (read: "type one-A") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white dwarf. Physically, carbon–oxygen white dwarfs with a low rate of rotation are limited to below 1.44 solar masses (). Beyond this "critical mass", they reignite and in some cases trigger a supernova explosion; this critical mass is often referred to as the Chandrasekhar mass, but is marginally different from the absolute Chandrasekhar limit, where electron degeneracy pressure is unable to prevent catastrophic collapse. If a white dwarf gradually accretes mass from a binary companion, or merges with a second white dwarf, the general hypothesis is that a white dwarf's core will reach the ignition temperature for carbon fusion as it approaches the Chandrasekhar mass. Within a few seconds of initiation of nuclear fusion, a substantial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fritz Zwicky
Fritz Zwicky (; ; February 14, 1898 – February 8, 1974) was a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and observational astronomy. In 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen dark matter, describing it as "'". From p 125: ''"Um, wie beobachtet, einen mittleren Dopplereffekt von 1000 km/sek oder mehr zu erhalten, müsste also die mittlere Dichte im Comasystem mindestens 400 mal grösser sein als die auf Grund von Beobachtungen an leuchtender Materie abgeleitete. Falls sich dies bewahrheiten sollte, würde sich also das überraschende Resultat ergeben, dass dunkle Materie in sehr viel grösserer Dichte vorhanden ist als leuchtende Materie."'' (In order to obtain an average Doppler effect of 1000 km/s or more, as observed, the average density in the Coma system would thus have to be at least 400 time ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmologist
Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', and in 1731 taken up in Latin by German philosopher Christian Wolff, in ''Cosmologia Generalis''. Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation myths and eschatology. In the science of astronomy it is concerned with the study of the chronology of the universe. Physical cosmology is the study of the observable universe's origin, its large-scale structures and dynamics, and the ultimate fate of the universe, including the laws of science that govern these areas. It is investigated by scientists, such as astronomers and physicists, as well as philosophers, such as metaphysicians, philosophers of physics, and philosophers of space and time. Because of this shared scope with philosophy, theories in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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