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Hun Kal (crater)
Hun Kal is a small (about 1.5 km in diameter) crater on Mercury that serves as the reference point for the planet's system of longitude. The longitude of Hun Kal's center is defined as being 20° W, thus establishing the planet's prime meridian. The name "Hun Kal" means '20' in the language of the Maya. Hun Kal was chosen as a reference point since the actual prime meridian was in shadow when '' Mariner 10'' photographed the region, hiding any features near 0° longitude from view. The prime meridian of Mercury is thermocentric, it runs through the point on the equator where the planet is hottest (due to the planet's rotation and orbit, the sun briefly retrogrades at noon at this point during perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ..., giving it more su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mayan Languages
The Mayan languagesIn linguistics, it is conventional to use ''Mayan'' when referring to the languages, or an aspect of a language. In other academic fields, ''Maya'' is the preferred usage, serving as both a singular and plural noun, and as the adjectival form. form a language family spoken in Mesoamerica, both in the south of Mexico and northern Central America. Mayan languages are spoken by at least 6 million Maya people, primarily in Guatemala, Mexico, Belize, El Salvador and Honduras. In 1996, Guatemala formally recognized 21 Mayan languages by name,Achiʼ is counted as a variant of Kʼicheʼ by the Guatemalan government. and Mexico recognizes eight within its territory. The Mayan language family is one of the best-documented and most studied in the Americas. Modern Mayan languages descend from the Proto-Mayan language, thought to have been spoken at least 5,000 years ago; it has been partially reconstructed using the comparative method. The proto-Mayan language diver ... [...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] |
Mercury (planet)
Mercury is the smallest planet in the Solar System and the closest to the Sun. Its orbit around the Sun takes 87.97 Earth days, the shortest of all the Sun's planets. It is named after the Roman god ' ( Mercury), god of commerce, messenger of the gods, and mediator between gods and mortals, corresponding to the Greek god Hermes (). Like Venus, Mercury orbits the Sun within Earth's orbit as an inferior planet, and its apparent distance from the Sun as viewed from Earth never exceeds 28°. This proximity to the Sun means the planet can only be seen near the western horizon after sunset or the eastern horizon before sunrise, usually in twilight. At this time, it may appear as a bright star-like object, but is more difficult to observe than Venus. From Earth, the planet telescopically displays the complete range of phases, similar to Venus and the Moon, which recurs over its synodic period of approximately 116 days. The synodic proximity of Mercury to Earth makes Mercury most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Longitude
Longitude (, ) is a geographic coordinate that specifies the east–west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Meridians are semicircular lines running from pole to pole that connect points with the same longitude. The prime meridian defines 0° longitude; by convention the International Reference Meridian for the Earth passes near the Royal Observatory in Greenwich, England on the island of Great Britain. Positive longitudes are east of the prime meridian, and negative ones are west. Because of the Earth's rotation, there is a close connection between longitude and time measurement. Scientifically precise local time varies with longitude: a difference of 15° longitude corresponds to a one-hour difference in local time, due to the differing position in relation to the Sun. Comparing local time to an absolute measure of time allows ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prime Meridian
A prime meridian is an arbitrary meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian (the 180th meridian in a 360°-system) form a great circle. This great circle divides a spheroid, like the Earth, into two hemispheres: the Eastern Hemisphere and the Western Hemisphere (for an east-west notational system). For Earth's prime meridian, various conventions have been used or advocated in different regions throughout history. The Earth's current international standard prime meridian is the IERS Reference Meridian. It is derived, but differs slightly, from the Greenwich Meridian, the previous standard. A prime meridian for a planetary body not tidally locked (or at least not in synchronous rotation) is entirely arbitrary, unlike an equator, which is determined by the axis of rotation. However, for celestial objects that are tidally locked (more specifically, synchronous), th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hun Kal Crater On Mercury
The Huns were a nomadic people who lived in Central Asia, the Caucasus, and Eastern Europe between the 4th and 6th century AD. According to European tradition, they were first reported living east of the Volga River, in an area that was part of Scythia at the time; the Huns' arrival is associated with the migration westward of an Iranian people, the Alans. By 370 AD, the Huns had arrived on the Volga, and by 430, they had established a vast, if short-lived, dominion in Europe, conquering the Goths and many other Germanic peoples living outside of Roman borders and causing many others to flee into Roman territory. The Huns, especially under their King Attila, made frequent and devastating raids into the Eastern Roman Empire. In 451, they invaded the Western Roman province of Gaul, where they fought a combined army of Romans and Visigoths at the Battle of the Catalaunian Fields, and in 452, they invaded Italy. After the death of Attila in 453, the Huns ceased to be a major thre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mariner 10
''Mariner 10'' was an American Robotic spacecraft, robotic space probe launched by NASA on 3 November 1973, to fly by the planets Mercury (planet), Mercury and Venus. It was the first spacecraft to perform flybys of multiple planets. ''Mariner 10'' was launched approximately two years after ''Mariner 9'' and was the last spacecraft in the Mariner program. (Mariner 11 and Mariner 12 were allocated to the Voyager program and redesignated ''Voyager 1'' and ''Voyager 2''.) The mission objectives were to measure Mercury's environment, atmosphere, surface, and body characteristics and to make similar investigations of Venus. Secondary objectives were to perform experiments in the interplanetary medium and to obtain experience with a dual-planet gravity assist mission. ''Mariner 10''s science team was led by Bruce C. Murray at the Jet Propulsion Laboratory. Design and trajectory ''Mariner 10'' was the first spacecraft to make use of an interplanetary gravitational slingshot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apparent Retrograde Motion
Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point. Direct motion or prograde motion is motion in the same direction as other bodies. While the terms ''direct'' and ''prograde'' are equivalent in this context, the former is the traditional term in astronomy. The earliest recorded use of ''prograde'' was in the early 18th century, although the term is now less common. Etymology The term ''retrograde'' is from the Latin word – "backward-step", the affix meaning "backwards" and "step". ''Retrograde'' is most commonly an adjective used to describe the path of a planet as it travels through the night sky, with respect to the zodiac, stars, and other bodies of the celestial canopy. In this context, the term refers to planets, as they appear from Earth, stopping briefly and reversing direction at certain times, though in reality, of course, we now understa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perihelion
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elliptic orbit. The name for each apsis is created from the prefixes ''ap-'', ''apo-'' (), or ''peri-'' (), each referring to the farthest and closest point to the primary body the affixing necessary suffix that describes the primary body in the orbit. In this case, the suffix for Earth is ''-gee'', so the apsides' names are ''apogee'' and ''perigee''. For the Sun, its suffix is ''-helion'', so the names are ''aphelion'' and ''perihelion''. According to Newton's laws of motion, all periodic orbits are ellipses. The barycenter of the two bodies may lie well within the bigger body—e.g., the Earth–Moon barycenter is about 75% of the way from Earth's center to its surface. If, compared to the larger mass, the smaller mass is negligible (e.g., f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Al-Jāhiz (crater)
Al-Jāhiz is a crater on Mercury. It has a diameter of 83 kilometers. Its name was adopted by the International Astronomical Union (IAU) in 1976. Al-Jāhiz is named for the Arab writer Al-Jahiz Abū ʿUthman ʿAmr ibn Baḥr al-Kinānī al-Baṣrī ( ar, أبو عثمان عمرو بن بحر الكناني البصري), commonly known as al-Jāḥiẓ ( ar, links=no, الجاحظ, ''The Bug Eyed'', born 776 – died December 868/Jan ..., who died in Basra, Iraq, in 869 C.E. Lu Hsun crater is southwest of Al-Jāhiz. References Impact craters on Mercury {{Mercury-planet-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lu Hsun (crater)
Lu Hsun is a crater on Mercury. It has a diameter of 98 kilometers. Its name was adopted by the International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ... (IAU) in 1976. Lu Hsun is named for the Chinese writer Lu Hsun, who lived from 1881 to 1936. Hollows are present on and around the central peak complex. Al-Jāhiz crater is northeast of Lu Hsun. File:Lu Hsun crater EN1063883199M.jpg, Oblique view of Lu Hsun crater (lower right), with bright hollows at the central peak File:Lu Hsun crater EN1007389680M.jpg, MESSENGER NAC image of central Lu Hsun References Impact craters on Mercury {{Mercury-planet-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Craters On Mercury
Impact may refer to: * Impact (mechanics), a high force or shock (mechanics) over a short time period * Impact, Texas, a town in Taylor County, Texas, US Science and technology * Impact crater, a meteor crater caused by an impact event * Impact event, the collision of a meteoroid, asteroid or comet with Earth * Impact factor, a measure of the citations to a science or social science journal Books and magazines * ''Impact'' (novel), a 2010 novel by Douglas Preston *''Impact Press'', a former Orlando, Florida-based magazine * Impact Magazines, a former UK magazine publisher * ''Impact'' (conservative magazine), a British political magazine * ''Impact'' (British magazine), a British action film magazine * ''Impact'', a French action film magazine spun off from ''Mad Movies'' * ''Impact'' (UNESCO magazine), a former UNESCO quarterly titled ''IMPACT of science on society'' * ''Impact'' (student magazine), a student magazine for the University of Nottingham, England * ''Bathimp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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