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Lexell (crater)
Lexell is a lunar impact crater that lies across the southeastern rim of the huge walled plain Deslandres, in the southern part of the Moon. It was named after Swedish-Russian mathematician and astronomer Anders Johan Lexell. To the northeast is the walled plain Walther, and to the south is Orontius, another walled plain. This is a somewhat irregular formation with a wide break in the northern rim. The western rim forms a low, arcing wall, and is overlain to the southwest by Lexell H after passing the rim of Deslandres. The rim peaks along the southeast, then comes to an end at a rugged promontory-like ridge. The interior floor has been resurfaced by lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ... to the northwest and in sections of the remainder of the floor. There are s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bayfordbury Observatory
Bayfordbury Observatory is the University of Hertfordshire's astronomy, astronomical and atmospheric physics remote sensing observatory, and one of the largest teaching observatories in the UK. It is located in the relatively dark countryside of Bayfordbury, Hertfordshire, 6 miles from the main university campus in Hatfield, Hertfordshire, Hatfield. The first telescope was built in 1969, and since then has been used as a teaching observatory for undergraduate students, staff and student research as well as for public outreach activities. History The first telescope, a 16-inch Newtonian telescope, Newtonian/Cassegrain reflector, Cassegrain telescope, was built on the site in 1969, one year after astronomy was first taught at the Hatfield Polytechnic. In 1970 the observatory was formally opened by Richard van der Riet Woolley, then Astronomer Royal. Over the years the number of telescopes has increased along with the size of astronomy department. On the 30th anniversary in 2000, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anders Johan Lexell
Anders Johan Lexell (24 December 1740 – ) was a Finnish-Swedish astronomer, mathematician, and physicist who spent most of his life in Imperial Russia, where he was known as Andrei Ivanovich Leksel (Андрей Иванович Лексель). Lexell made important discoveries in polygonometry and celestial mechanics; the latter led to a comet named in his honour. La Grande Encyclopédie states that he was the prominent mathematician of his time who contributed to spherical trigonometry with new and interesting solutions, which he took as a basis for his research of comet and planet motion. His name was given to a theorem of spherical triangles. Lexell was one of the most prolific members of the Russian Academy of Sciences at that time, having published 66 papers in 16 years of his work there. A statement attributed to Leonhard Euler expresses high approval of Lexell's works: "Besides Lexell, such a paper could only be written by D'Alambert or me". Daniel Bernoulli als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lunar Craters
Lunar craters are impact craters on Earth's Moon. The Moon's surface has many craters, all of which were formed by impacts. The International Astronomical Union currently recognizes 9,137 craters, of which 1,675 have been dated. History The word ''crater'' was adopted from the Greek word for "vessel" (, a Greek vessel used to mix wine and water). Galileo built his first telescope in late 1609, and turned it to the Moon for the first time on November 30, 1609. He discovered that, contrary to general opinion at that time, the Moon was not a perfect sphere, but had both mountains and cup-like depressions. These were named craters by Johann Hieronymus Schröter (1791), extending its previous use with volcanoes. Robert Hooke in ''Micrographia'' (1665) proposed two hypotheses for lunar crater formation: one, that the craters were caused by projectile bombardment from space, the other, that they were the products of subterranean lunar volcanism. Scientific opinion as to the origin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Lunar impact craters range from microscopic craters on lunar rocks returned by the Apollo Program and small, simple, bowl-shaped depressions in the lunar regolith to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth. Impact craters are the dominant geographic features on many solid Solar System objects including the Moon, Mercury, Callisto, Ganymede and most small moons and asteroids. On other planets and moons that experience more active surface geological processes, such as Earth, Venus, Europa, Io and Titan, visible impact craters are less common because they become eroded ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deslandres (crater)
Deslandres is the heavily worn and distorted remains of a Lunar craters, lunar impact crater. It is located to the southeast of the Mare Nubium, in the rugged southern highlands of the Moon. In dimension it is the third-largest crater formation on the visible Moon, being beaten only by Clavius (crater), Clavius (231 km) and by the 303-kilometer-diameter walled plain Bailly (crater), Bailly. The northern and eastern parts of the floor display a relatively level surface, but it is pock-marked with numerous craters. There is a small region of mare material, due to basaltic lava, along the eastern interior floor. The crater Walther (crater), Walther is attached to the remnant of the eastern rim, and Ball (crater), Ball intrudes into the southwestern rim. The crater remnant Lexell (crater), Lexell has broken across the southeastern rim, forming a "harbor" in the crater floor due to the wide gap in its northern rim. The irregular crater Regiomontanus (crater), Regiomontanus is attached ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of Australia). The Moon is a planetary-mass object with a differentiated rocky body, making it a satellite planet under the geophysical definitions of the term and larger than all known dwarf planets of the Solar System. It lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth's at , with Jupiter's moon Io being the only satellite in the Solar System known to have a higher surface gravity and density. The Moon orbits Earth at an average distance of , or about 30 times Earth's diameter. Its gravitational influence is the main driver of Earth's tides and very slowly lengthens Earth's day. The Moon's orbit around Earth has a sidereal period of 27.3 days. During each synodic period ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Walther (crater)
Walther is an ancient lunar impact crater located in the southern highland region of the Moon. It is joined along the western rim to the crater Deslandres. To the northeast is Aliacensis, and joined to the southeast rim is the irregular Nonius. Description The rim of Walther is complex, heavily eroded and incised by lesser impacts. The wall retains a generally circular form, but many of its features have been worn away and there is a slight protruding bulge in the western rim. The floor has been resurfaced after the original impact, leaving the southwestern half relatively smooth. In the northwest quadrant is an offset central peak that has been worn and impacted by several small craters. Names Walther is named after the German astronomer Bernhard Walther. Like many of the craters on the Moon's near side, it was named (in the Latin form, 'Valtherus') by Giovanni Riccioli, whose 1651 nomenclature system has become standardized. Earlier lunar cartographers had given the featur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orontius (crater)
Orontius is a lunar impact crater that lies in the heavily cratered southern highlands of the Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...'s near side. It was named after 16th century French mathematician Oronce Fine. It is located to the northwest of the prominent ray crater Tycho, and south and east of the large walled plain Deslandres. The eastern part of the crater is overlain by the smaller crater Huggins, which is overlain in turn on its eastern rim by the still smaller Nasireddin, the trio forming a crater chain of diminishing dimensions. Joined to the southern rim is the crater Saussure. To the southwest, just east of Tycho, is Pictet. The rim of Orontius is battered, worn, and overlain by a number of different craters. A pair of craters to the west have i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from . The volcanic rock resulting from subsequent cooling is also often called ''lava''. A lava flow is an outpouring of lava during an effusive eruption. (An explosive eruption, by contrast, produces a mixture of volcanic ash and other fragments called tephra, not lava flows.) The viscosity of most lava is about that of ketchup, roughly 10,000 to 100,000 times that of water. Even so, lava can flow great distances before cooling causes it to solidify, because lava exposed to air quickly develops a solid crust that insulates the remaining liquid lava, helping to keep it hot and inviscid enough to continue flowing. The word ''lava'' comes from Italian and is probably derived from the Latin word ''labes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palimpsest
In textual studies, a palimpsest () is a manuscript page, either from a scroll or a book, from which the text has been scraped or washed off so that the page can be reused for another document. Parchment was made of lamb, calf, or kid skin and was expensive and not readily available, so, in the interest of economy, a page was often re-used by scraping off the previous writing. In colloquial usage, the term ''palimpsest'' is also used in architecture, archaeology and geomorphology to denote an object made or worked upon for one purpose and later reused for another; for example, a monumental brass the reverse blank side of which has been re-engraved. Etymology The word ''palimpsest'' derives from the Latin '' palimpsestus'', which derives from the Ancient Greek παλίμψηστος (, from + = 'again' + 'scrape'), a compound word that describes the process: "The original writing was scraped and washed off, the surface resmoothed, and the new literary material written o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding the National Advisory Committee for Aeronautics (NACA), to give the U.S. space development effort a distinctly civilian orientation, emphasizing peaceful applications in space science. NASA has since led most American space exploration, including Project Mercury, Project Gemini, the 1968-1972 Apollo Moon landing missions, the Skylab space station, and the Space Shuttle. NASA supports the International Space Station and oversees the development of the Orion spacecraft and the Space Launch System for the crewed lunar Artemis program, Commercial Crew spacecraft, and the planned Lunar Gateway space station. The agency is also responsible for the Launch Services Program, which provides oversight of launch operations and countdown management f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambridge University Press
Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by Henry VIII of England, King Henry VIII in 1534, it is the oldest university press A university press is an academic publishing house specializing in monographs and scholarly journals. Most are nonprofit organizations and an integral component of a large research university. They publish work that has been reviewed by schola ... in the world. It is also the King's Printer. Cambridge University Press is a department of the University of Cambridge and is both an academic and educational publisher. It became part of Cambridge University Press & Assessment, following a merger with Cambridge Assessment in 2021. With a global sales presence, publishing hubs, and offices in more than 40 Country, countries, it publishes over 50,000 titles by authors from over 100 countries. Its publishing includes more than 380 academic journals, monographs, reference works, school and uni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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