1.
Sunspot
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Sunspots are temporary phenomena on the photosphere of the Sun that appear as dark spots compared with surrounding regions. They are areas of reduced surface temperature caused by concentrations of field flux that inhibit convection. Sunspots usually appear in pairs of magnetic polarity. Their number varies according to the approximately 11-year solar cycle, individual sunspots may endure anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun with sizes ranging from 16 kilometers to 160,000 kilometers in diameter, the larger variety are visible from Earth without the aid of a telescope. They may travel at speeds, or proper motions of a few hundred meters per second when they first emerge. Indicating intense magnetic activity, sunspots accompany secondary phenomena such as coronal loops, most solar flares and coronal mass ejections originate in magnetically active regions around visible sunspot groupings. Similar phenomena indirectly observed on other than the sun are commonly called starspots. Although they are at temperatures of roughly 3, 000–4,500 K, isolated from the surrounding photosphere a sunspot would be brighter than the Moon. If the stress on the tubes reaches a limit, they curl up. Convection is inhibited at the points, the energy flux from the Suns interior decreases. The Wilson effect implies that sunspots are depressions on the Suns surface, observations using the Zeeman effect show that prototypical sunspots come in pairs with opposite magnetic polarity. From cycle to cycle, the polarities of leading and trailing sunspots change from north/south to south/north, magnetic pressure should tend to remove field concentrations, causing the sunspots to disperse, but sunspot lifetimes are measured in days to weeks. Sunspot activity cycles about every eleven years, the point of highest sunspot activity during a cycle is known as solar maximum, and the point of lowest activity as solar minimum. This period is observed in most other solar activity and is linked to a variation in the solar magnetic field that changes polarity with this period. Early in the cycle, sunspots appear in the latitudes and then move towards the equator as the cycle approaches maximum. Spots from two adjacent cycles can co-exist for some time, spots from adjacent cycles can be distinguished by direction of their magnetic field. The Wolf number sunspot index counts the number of sunspots
2.
Mercury (planet)
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Mercury is the smallest and innermost planet in the Solar System. Its orbital period around the Sun of 88 days is the shortest of all the planets in the Solar System and it is named after the Roman deity Mercury, the messenger to the gods. Like Venus, Mercury orbits the Sun within Earths orbit as a planet, so it can only be seen visually in the morning or the evening sky. Also, like Venus and the Moon, the displays the complete range of phases as it moves around its orbit relative to Earth. Seen from Earth, this cycle of phases reoccurs approximately every 116 days, although Mercury can appear as a bright star-like object when viewed from Earth, its proximity to the Sun often makes it more difficult to see than Venus. Mercury is tidally or gravitationally locked with the Sun in a 3,2 resonance, as seen relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun. As seen from the Sun, in a frame of reference that rotates with the orbital motion, an observer on Mercury would therefore see only one day every two years. Mercurys axis has the smallest tilt of any of the Solar Systems planets, at aphelion, Mercury is about 1.5 times as far from the Sun as it is at perihelion. Mercurys surface appears heavily cratered and is similar in appearance to the Moons, the polar regions are constantly below 180 K. The planet has no natural satellites. Mercury is one of four planets in the Solar System. It is the smallest planet in the Solar System, with a radius of 2,439.7 kilometres. Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede, Mercury consists of approximately 70% metallic and 30% silicate material. Mercurys density is the second highest in the Solar System at 5.427 g/cm3, Mercurys density can be used to infer details of its inner structure. Although Earths high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller, therefore, for it to have such a high density, its core must be large and rich in iron. Geologists estimate that Mercurys core occupies about 55% of its volume, Research published in 2007 suggests that Mercury has a molten core. Surrounding the core is a 500–700 km mantle consisting of silicates, based on data from the Mariner 10 mission and Earth-based observation, Mercurys crust is estimated to be 35 km thick. One distinctive feature of Mercurys surface is the presence of narrow ridges
3.
Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions
4.
Curiosity (rover)
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Curiosity is a car-sized robotic rover exploring Gale Crater on Mars as part of NASAs Mars Science Laboratory mission. Curiosity was launched from Cape Canaveral on November 26,2011, at 15,02 UTC aboard the MSL spacecraft, the Bradbury Landing site was less than 2.4 km from the center of the rovers touchdown target after a 560 million km journey. Curiositys design will serve as the basis for the planned Mars 2020 rover, in December 2012, Curiositys two-year mission was extended indefinitely. As of April 7,2017, Curiosity has been on Mars for 1659 sols since landing on August 6,2012, the mission will also help prepare for human exploration. This data would be important for a manned mission. The remaining mass of the MSL craft was discarded in the process of carrying out this task, dimensions, Curiosity has a mass of 899 kg including 80 kg of scientific instruments. The rover is 2.9 m long by 2.7 m wide by 2.2 m in height, power source, Curiosity is powered by a radioisotope thermoelectric generator, like the successful Viking 1 and Viking 2 Mars landers in 1976. Radioisotope power systems are generators that produce electricity from the decay of isotopes, such as plutonium-238. Heat given off by the decay of this isotope is converted into electric voltage by thermocouples, providing constant power during all seasons and through the day, waste heat can be used via pipes to warm systems, freeing electrical power for the operation of the vehicle and instruments. Curiositys RTG is fueled by 4.8 kg of plutonium-238 dioxide supplied by the U. S. Department of Energy. The MMRTG produces less power over time as its plutonium fuel decays, at its minimum lifetime of 14 years, electrical power output is down to 100 watts. The power source will generate 9 MJ each day, much more than the solar panels of the Mars Exploration Rovers, the electrical output from the MMRTG charges two rechargeable lithium-ion batteries. This enables the power subsystem to meet power demands of rover activities when the demand temporarily exceeds the generator’s steady output level. Each battery has a capacity of about 42 ampere-hours, heat rejection system, The temperatures at the landing site can vary from −127 to 40 °C, therefore, the thermal system will warm the rover for most of the Martian year. It uses fluid pumped through 60 m of tubing in the body so that sensitive components are kept at optimal temperatures. The HRS also has the ability to cool components if necessary, the computers run the VxWorks real-time operating system. Each computers memory includes 256 kB of EEPROM,256 MB of DRAM, for comparison, the Mars Exploration Rovers used 3 MB of EEPROM,128 MB of DRAM, and 256 MB of flash memory. The RCE computers use the RAD750 CPU, which is a successor to the RAD6000 CPU of the Mars Exploration Rovers
5.
Mars
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Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is referred to as the Red Planet because the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, Mars is the site of Olympus Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the northern hemisphere covers 40% of the planet, Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan, there are ongoing investigations assessing the past habitability potential of Mars, as well as the possibility of extant life. Future astrobiology missions are planned, including the Mars 2020 and ExoMars rovers, liquid water cannot exist on the surface of Mars due to low atmospheric pressure, which is about 6⁄1000 that of the Earths, except at the lowest elevations for short periods. The two polar ice caps appear to be largely of water. The volume of ice in the south polar ice cap, if melted. On November 22,2016, NASA reported finding a large amount of ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior, Mars can easily be seen from Earth with the naked eye, as can its reddish coloring. Its apparent magnitude reaches −2.91, which is surpassed only by Jupiter, Venus, the Moon, optical ground-based telescopes are typically limited to resolving features about 300 kilometers across when Earth and Mars are closest because of Earths atmosphere. Mars is approximately half the diameter of Earth with an area only slightly less than the total area of Earths dry land. Mars is less dense than Earth, having about 15% of Earths volume and 11% of Earths mass, the red-orange appearance of the Martian surface is caused by iron oxide, or rust. It can look like butterscotch, other common colors include golden, brown, tan. Like Earth, Mars has differentiated into a metallic core overlaid by less dense materials. Current models of its interior imply a core with a radius of about 1,794 ±65 kilometers, consisting primarily of iron and this iron sulfide core is thought to be twice as rich in lighter elements than Earths. The core is surrounded by a mantle that formed many of the tectonic and volcanic features on the planet
6.
Transit (astronomy)
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The word transit refers to cases where the nearer object appears considerably smaller than the more distant object. Cases where the object appears larger and completely hides the more distant object are known as occultations. One example of a transit involves the motion of a planet between an observer and the Sun. This can happen only with inferior planets, namely Mercury and Venus, however, as seen from outer planets such as Mars, the Earth itself transits the Sun on occasion. The term can also be used to describe the motion of a satellite across its parent planet, for one of the Galilean satellites across Jupiter. A transit requires three bodies to be lined up in a single line, more rare are cases where four bodies are lined up. The one closest to the present occurred on 27 June 1586, when Mercury transited the Sun as seen from Venus at the time as a transit of Mercury from Saturn. In recent years the discovery of planets has excited interest in the possibility of detecting their transits across their own stellar primaries. HD 209458b is the first such transiting planet to be discovered, in rare cases, one planet can pass in front of another. If the nearer planet appears smaller than the distant one. During a transit there are four contacts, when the circumference of the circle touches the circumference of the large circle at a single point. Historically, measuring the time of each point of contact was one of the most accurate ways to determine the positions of astronomical bodies. No missions were planned to coincide with the transit of Earth visible from Mars on 11 May 1984, consequently, the next opportunity to observe such an alignment will be in 2084. On December 21,2012, the Cassini–Huygens probe, in orbit around Saturn, on 3 June 2014, the Mars rover Curiosity observed the planet Mercury transiting the Sun, marking the first time a planetary transit has been observed from a celestial body besides Earth. 1989, ISBN 0-943396-25-5 Jean Meeus, Astronomical Tables of the Sun, Moon,1995, ISBN 0-943396-45-X Karl Ramsayer, Geodätische Astronomie, Vol. 2a of Handbuch der Vermessungskunde,900 p. J. B. Metzler, Stuttgart 1969
7.
Planet
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The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Several planets in the Solar System can be seen with the naked eye and these were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, in 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of mass based on where or what they orbit. The planets were thought by Ptolemy to orbit Earth in deferent, at about the same time, by careful analysis of pre-telescopic observation data collected by Tycho Brahe, Johannes Kepler found the planets orbits were not circular but elliptical. As observational tools improved, astronomers saw that, like Earth, the planets rotated around tilted axes, and some shared such features as ice caps and seasons. Since the dawn of the Space Age, close observation by space probes has found that Earth and the planets share characteristics such as volcanism, hurricanes, tectonics. Planets are generally divided into two types, large low-density giant planets, and smaller rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System, in order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites, several thousands of planets around other stars have been discovered in the Milky Way. e. in the habitable zone. On December 20,2011, the Kepler Space Telescope team reported the discovery of the first Earth-sized extrasolar planets, Kepler-20e and Kepler-20f, orbiting a Sun-like star, Kepler-20. A2012 study, analyzing gravitational microlensing data, estimates an average of at least 1.6 bound planets for every star in the Milky Way, around one in five Sun-like stars is thought to have an Earth-sized planet in its habitable zone. The idea of planets has evolved over its history, from the lights of antiquity to the earthly objects of the scientific age. The concept has expanded to include not only in the Solar System. The ambiguities inherent in defining planets have led to much scientific controversy, the five classical planets, being visible to the naked eye, have been known since ancient times and have had a significant impact on mythology, religious cosmology, and ancient astronomy. In ancient times, astronomers noted how certain lights moved across the sky, as opposed to the fixed stars, ancient Greeks called these lights πλάνητες ἀστέρες or simply πλανῆται, from which todays word planet was derived. In ancient Greece, China, Babylon, and indeed all pre-modern civilizations, it was almost universally believed that Earth was the center of the Universe and that all the planets circled Earth. The first civilization known to have a theory of the planets were the Babylonians
8.
Transit of Venus
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A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and a superior planet, becoming visible against the solar disk. During a transit, Venus can be seen from Earth as a black disk moving across the face of the Sun. The duration of such transits is usually measured in hours, a transit is similar to a solar eclipse by the Moon. While the diameter of Venus is more than 3 times that of the Moon, Venus appears smaller, Transits of Venus are among the rarest of predictable astronomical phenomena. They occur in a pattern that repeats every 243 years. The periodicity is a reflection of the fact that the periods of Earth. The last transit of Venus was on 5 and 6 June 2012, and was the last Venus transit of the 21st century, the previous pair of transits were in December 1874 and December 1882. The next transits of Venus will be on 10–11 December 2117, Venus transits are historically of great scientific importance as they were used to gain the first realistic estimates of the size of the Solar System. Observations of the 1639 transit, combined with the principle of parallax, the 2012 transit provided scientists with a number of other research opportunities, particularly in the refinement of techniques to be used in the search for exoplanets. Venus, with an orbit inclined by 3. 4° relative to the Earths, although the inclination between these two orbital planes is only 3. 4°, Venus can be as far as 9. 6° from the Sun when viewed from the Earth at inferior conjunction. Since the angular diameter of the Sun is about half a degree, sequences of transits usually repeat every 243 years. After this period of time Venus and Earth have returned to nearly the same point in their respective orbits. During the Earths 243 sidereal orbital periods, which total 88,757.3 days, Venus completes 395 sidereal orbital periods of 224.701 days each and this period of time corresponds to 152 synodic periods of Venus. Prior to 1518, the pattern of transits was 8,113.5 and 121.5 years, the current pattern will continue until 2846, when it will be replaced by a pattern of 105.5,129.5 and 8 years. Thus, the 243-year cycle is relatively stable, but the number of transits, for instance, there is a series which ended in 541 BC, and the series which includes 2117 only started in AD1631. Ancient Indian, Greek, Egyptian, Babylonian and Chinese observers knew of Venus, the early Greek astronomers called Venus by two names—Hesperus the evening star and Phosphorus the morning star. Pythagoras is credited with realizing they were the same planet, there is no evidence that any of these cultures knew of the transits. Venus was important to ancient American civilizations, in particular for the Maya, who called it Noh Ek, the Great Star or Xux Ek, the Wasp Star, they embodied Venus in the form of the god Kukulkán
9.
Mars rover
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A Mars rover is an automated motor vehicle that propels itself across the surface of the planet Mars upon arrival. There have been four successful robotically operated Mars rovers, the Jet Propulsion Laboratory managed the Mars Pathfinder mission and its now inactive Sojourner rover. It currently manages the Mars Exploration Rover missions active Opportunity rover and inactive Spirit, and, as part of the Mars Science Laboratory mission, the search for evidence of habitability, taphonomy, and organic carbon on the planet Mars is now a primary NASA objective. Several rovers have been sent to Mars, Mars 2, Prop-M rover,1971, the Mars 2 and 3 spacecraft from the USSR had identical 4.5 kg Prop-M rovers. They were to move on skis while connected to the landers with cables, Mars 3, Prop-M rover,1971, lost when Mars 3 lander stopped communicating about 20 seconds after landing. Sojourner rover, Mars Pathfinder, landed successfully on July 4,1997, communications were lost on September 27,1997. Beagle 2, Planetary Undersurface Tool, lost with Beagle 2 on deployment from Mars Express in 2003. A compressed spring mechanism was designed to allow movement across the surface at a rate of 1 cm per 5 seconds and to burrow into the ground and collect a subsurface sample in a cavity in its tip. Spirit, Mars Exploration Rover, launched on June 10,2003 at 13,58,47 EDT, nearly 6 years after the original mission limit, Spirit had covered a total distance of 7.73 km but its wheels became trapped in sand. Around January 26,2010, NASA conceded defeat in its efforts to free the rover, the last communication received from the rover was on March 22,2010, and NASA ceased attempts to re-establish communication on May 25,2011. Opportunity, Mars Exploration Rover, launched on July 7,2003 at 23,18,15 EDT, Opportunity is still operational and mobile as of April 7,2017. Curiosity, Mars Science Laboratory, by NASA, was launched November 26,2011 at 10,02 EST, Curiosity Rover is still operational as of April 7,2017. Mars rovers in development include, ExoMars, by the ESA, the rover will use stained glass to prevent UV from changing image colors, allowing for true color images of the surface of Mars. Chinese Mars Rover, has planned for a pre-2020 launch. MESR, REX, and MRPTA have a destination of Mars. Mars 2020, a NASA rover based on the current rover Curiosity,2020 Chinese Mars Mission, would include an orbiter, lander and small rover. One experimental design, not proposed for any mission, is, Mars Tumbleweed Rover. Many Mars Design Reference Mission include rovers as do some Mars sample return Astrobiology Field Laboratory, Mars Astrobiology Explorer-Cacher, cancelled 2011 Mars Surveyor 2001 rover, NASA distinguishes between mission objectives and science objectives
10.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
11.
Solar System
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The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being significantly smaller objects, such as dwarf planets, of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury. The Solar System formed 4.6 billion years ago from the collapse of a giant interstellar molecular cloud. The vast majority of the mass is in the Sun. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being composed of rock. The four outer planets are giant planets, being more massive than the terrestrials. All planets have almost circular orbits that lie within a flat disc called the ecliptic. The Solar System also contains smaller objects, the asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptunes orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity. Such objects are categorized as dwarf planets, identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds. Six of the planets, at least four of the dwarf planets, each of the outer planets is encircled by planetary rings of dust and other small objects. The solar wind, a stream of charged particles flowing outwards from the Sun, the heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium, it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, the Solar System is located in the Orion Arm,26,000 light-years from the center of the Milky Way. For most of history, humanity did not recognize or understand the concept of the Solar System, the invention of the telescope led to the discovery of further planets and moons. The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99. 86% of the known mass. The Suns four largest orbiting bodies, the giant planets, account for 99% of the mass, with Jupiter. The remaining objects of the Solar System together comprise less than 0. 002% of the Solar Systems total mass, most large objects in orbit around the Sun lie near the plane of Earths orbit, known as the ecliptic
12.
Orbital node
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An orbital node is one of the two points where an orbit crosses a plane of reference to which it is inclined. An orbit that is contained in the plane of reference has no nodes, common planes of reference include, For a geocentric orbit, the Earths equatorial plane. In this case, non-inclined orbits are called equatorial, for a heliocentric orbit, the ecliptic. In this case, non-inclined orbits are called ecliptic, for an orbit outside the Solar System, the plane through the primary perpendicular to a line through the observer and the primary. If a reference direction from one side of the plane of reference to the other is defined, the two nodes can be distinguished. For geocentric and heliocentric orbits, the node is where the orbiting object moves north through the plane of reference. The position of the node may be used as one of a set of parameters, called orbital elements and this is done by specifying the longitude of the ascending node The line of nodes is the intersection of the objects orbital plane with the plane of reference. It passes through the two nodes, the symbol of the ascending node is, and the symbol of the descending node is. In medieval and early times the ascending and descending nodes were called the dragons head and dragons tail. These terms originally referred to the times when the Moon crossed the apparent path of the sun in the sky, also, corruptions of the Arabic term such as ganzaar, genzahar, geuzaar and zeuzahar were used in the medieval West to denote either of the nodes. Pp. 196–197, p.65, pp. 95–96, the Greek terms αναβιβάζων and καταβιβάζων were also used for the ascending and descending nodes, giving rise to the English words anabibazon and catabibazon. For the orbit of the Moon around the Earth, the plane is taken to be the ecliptic. The gravitational pull of the Sun upon the Moon causes its nodes, called the nodes, to precess gradually westward. Eclipse Euler angles Longitude of the ascending node
13.
Pierre Gassendi
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Pierre Gassendi was a French philosopher, priest, astronomer, and mathematician. While he held a position in south-east France, he also spent much time in Paris. He was also an active observational scientist, publishing the first data on the transit of Mercury in 1631, the lunar crater Gassendi is named after him. He wrote numerous works, and some of the positions he worked out are considered significant. Richard Popkin indicates that Gassendi was one of the first thinkers to formulate the scientific outlook. He clashed with his contemporary Descartes on the possibility of certain knowledge and his best known intellectual project attempted to reconcile Epicurean atomism with Christianity. Gassendi was born at Champtercier, near Digne, in France to Antoine Gassend, a youthful prodigy, at a very early age he showed academic potential and attended the college at Digne, where he displayed a particular aptitude for languages and mathematics. Soon afterwards he entered the University of Aix-en-Provence, to study philosophy under Philibert Fesaye, in 1612 the college of Digne called him to lecture on theology. Four years later he received the degree of Doctor of Theology at Avignon, in the same year he answered a call to the chair of philosophy at Aix-en-Provence University, and seems gradually to have withdrawn from theology. He lectured principally on the Aristotelian philosophy, conforming as far as possible to the traditional methods while he followed with interest the discoveries of Galileo. He came into contact with the astronomer Joseph Gaultier de la Vallette, in 1623 the Society of Jesus took over the University of Aix. They filled all positions with Jesuits, so Gassendi was required to find another institution and he left, returning to Digne, and then travelled for the chapter to Grenoble. In 1624 he printed the first part of his Exercitationes paradoxicae adversus Aristoteleos and he spent some time with his patron Nicolas Peiresc. After 1628 Gassendi travelled in Flanders and in Holland where he encountered Isaac Beeckman and he returned to France in 1631, and two years later became provost of Digne Cathedral. During this time he wrote some works, at the insistence of Marin Mersenne and they included his examination of the mystical philosophy of Robert Fludd, an essay on parhelia, and some observations on the transit of Mercury. Gassendi then spent some years travelling through Provence with the duke of Angoulême, during this period he wrote only the one literary work, his Life of Peiresc, whose death in 1637 seemed to afflict him deeply, it received frequent reprintings and an English translation. He returned to Paris in 1641, where he met Thomas Hobbes, in 1642 Mersenne engaged him in controversy with René Descartes. His objections to the propositions of Descartes appeared in print in 1642
14.
Johannes Kepler
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Johannes Kepler was a German mathematician, astronomer, and astrologer. A key figure in the 17th-century scientific revolution, he is best known for his laws of motion, based on his works Astronomia nova, Harmonices Mundi. These works also provided one of the foundations for Isaac Newtons theory of universal gravitation, Kepler was a mathematics teacher at a seminary school in Graz, where he became an associate of Prince Hans Ulrich von Eggenberg. Later he became an assistant to the astronomer Tycho Brahe in Prague and he was also a mathematics teacher in Linz, and an adviser to General Wallenstein. Kepler lived in an era when there was no distinction between astronomy and astrology, but there was a strong division between astronomy and physics. Kepler was born on December 27, the feast day of St John the Evangelist,1571 and his grandfather, Sebald Kepler, had been Lord Mayor of the city. By the time Johannes was born, he had two brothers and one sister and the Kepler family fortune was in decline and his father, Heinrich Kepler, earned a precarious living as a mercenary, and he left the family when Johannes was five years old. He was believed to have died in the Eighty Years War in the Netherlands and his mother Katharina Guldenmann, an innkeepers daughter, was a healer and herbalist. Born prematurely, Johannes claimed to have weak and sickly as a child. Nevertheless, he often impressed travelers at his grandfathers inn with his phenomenal mathematical faculty and he was introduced to astronomy at an early age, and developed a love for it that would span his entire life. At age six, he observed the Great Comet of 1577, in 1580, at age nine, he observed another astronomical event, a lunar eclipse, recording that he remembered being called outdoors to see it and that the moon appeared quite red. However, childhood smallpox left him with vision and crippled hands. In 1589, after moving through grammar school, Latin school, there, he studied philosophy under Vitus Müller and theology under Jacob Heerbrand, who also taught Michael Maestlin while he was a student, until he became Chancellor at Tübingen in 1590. He proved himself to be a mathematician and earned a reputation as a skilful astrologer. Under the instruction of Michael Maestlin, Tübingens professor of mathematics from 1583 to 1631 and he became a Copernican at that time. In a student disputation, he defended heliocentrism from both a theoretical and theological perspective, maintaining that the Sun was the source of motive power in the universe. Despite his desire to become a minister, near the end of his studies, Kepler was recommended for a position as teacher of mathematics and he accepted the position in April 1594, at the age of 23. Keplers first major work, Mysterium Cosmographicum, was the first published defense of the Copernican system
15.
Jeremiah Horrocks
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Jeremiah Horrocks, sometimes given as Jeremiah Horrox, was an English astronomer. Jeremiah Horrocks was born at Lower Lodge Farm in Toxteth Park and his father James had moved to Toxteth Park to be apprenticed to Thomas Aspinwall, a watchmaker, and subsequently married his masters daughter Mary. Both families were well educated Puritans, the Horrocks sent their sons to the University of Cambridge. For their unorthodox beliefs the Puritans were excluded from public office, in 1632 Horrocks matriculated at Emmanuel College at the University of Cambridge as a sizar. At Cambridge he associated with the mathematician John Wallis and the platonist John Worthington, at that time he was one of only a few at Cambridge to accept Copernicuss revolutionary heliocentric theory, and he studied the works of Johannes Kepler, Tycho Brahe and others. In 1635 for reasons not clear Horrocks left Cambridge without graduating, now committed to the study of astronomy, Horrocks began to collect astronomical books and equipment, by 1638 he owned the best telescope he could find. Liverpool was a town so navigational instruments such as the astrolabe. But there was no market for the very specialised astronomical instruments he needed and he was well placed to do this, his father and uncles were watchmakers with expertise in creating precise instruments. While a youth he read most of the treatises of his day and marked their weaknesses. Tradition has it that after he left home he supported himself by holding a curacy in Much Hoole, near Preston in Lancashire, according to local tradition in Much Hoole, he lived at Carr House, within the Bank Hall Estate, Bretherton. Carr House was a property owned by the Stones family who were prosperous farmers and merchants. Horrocks was the first to demonstrate that the Moon moved in a path around the Earth. He anticipated Isaac Newton in suggesting the influence of the Sun as well as the Earth on the moons orbit, in the Principia Newton acknowledged Horrockss work in relation to his theory of lunar motion. In the final months of his life Horrocks made detailed studies of tides in attempting to explain the nature of causation of tidal movements. Keplers tables had predicted a near-miss of a transit of Venus in 1639 but, having made his own observations of Venus for years, Horrocks predicted a transit would indeed occur. Horrocks made a simple helioscope by focusing the image of the Sun through a telescope onto a plane surface, from his location in Much Hoole he calculated the transit would begin at approximately 3,00 pm on 24 November 1639, Julian calendar. The weather was cloudy but he first observed the tiny black shadow of Venus crossing the Sun at about 3,15 pm, the 1639 transit was also observed by William Crabtree from his home in Broughton near Manchester. His figure of 95 million kilometres was far from the 150 million kilometres known today and it presented Horrocks enthusiastic and romantic nature, including humorous comments and passages of original poetry
16.
Surat
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Surat, is a port city previously known as Suryapur. It is the capital and former princely state in the Indian state of Gujarat. It is the eighth largest city and ninth largest urban agglomeration in India, Surat is the 3rd cleanest city of India, and 4th fastest growing city of the world. Surat is famous for its food, textile, and diamonds, Surat polishes over 90 percent of the worlds rough diamond. It is the capital of the Surat district. The city is located 284 kilometres south of the capital, Gandhinagar,265 kilometres south of Ahmedabad. The city centre is located 22 km south of the Tapti River, a moat divides the older parts of the city, with their narrow streets and historical houses, from the newer suburbs. Surat had a population of 4.5 million at the 2011 census, making it the second largest city in the state of Gujarat and it is the eighth largest city and ninth largest urban agglomeration of India. Surat is the 34th-largest city by area and 4th-fastest developing cities in a study conducted by the City Mayors Foundation, the city registered an annualised GDP growth rate of 11.5 per cent over the seven fiscal years between 2001 and 2008. Surat was awarded best city by the Annual Survey of Indias City-Systems in 2013, Surat is selected as the first smart IT city in India which is being constituted by the Microsoft CityNext Initiative tied up with IT services majors Tata Consultancy Services and Wipro. The city has 2.97 million internet users which is about 65% of total population, Surat was selected in 2015 for an IBM Smarter Cities Challenge grant. Surat has been selected as one of twenty Indian cities to be developed as a city under PM Narendra Modis flagship Smart Cities Mission. Surat is mentioned in Sanskrit epic, the Mahābhārata, when Lord Krishna stopped there on his way from Mathura to Dwarka, the Parsis began to settle there in the 8th century. Local Hindu traditions state that the city was founded in the last years of the fifteenth century A. C. E. by a Brahman named Gopi, in 1512 and again in 1530 Surat was ravaged by the Portuguese Empire. In 1513, the Portuguese traveller Duarte Barbosa described Surat as an important seaport, frequented by ships from Malabar. By 1520, the name of the city was Surat, when the harbour in Cambay began to silt up toward the end of fifteenth century, Surat eclipsed Cambay as the major port of western India. At the end of the 16th century, the Portuguese were undisputed masters of the Surat sea trade, on the banks of the Tapti River, there is still a picturesque fortress that was built in 1540. In 1608, ships from the English East India Company started docking in Surat, using it as a trade, the city was made the seat of a presidency of the East India Company after the success of the embassy God of Wealth
17.
Charles II of England
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Charles II was king of England, Scotland and Ireland. He was king of Scotland from 1649 until his deposition in 1651, Charles IIs father, Charles I, was executed at Whitehall on 30 January 1649, at the climax of the English Civil War. Cromwell defeated Charles II at the Battle of Worcester on 3 September 1651, Cromwell became virtual dictator of England, Scotland and Ireland, and Charles spent the next nine years in exile in France, the Dutch Republic and the Spanish Netherlands. A political crisis followed the death of Cromwell in 1658 resulted in the restoration of the monarchy. On 29 May 1660, his 30th birthday, he was received in London to public acclaim, after 1660, all legal documents were dated as if he had succeeded his father as king in 1649. Charless English parliament enacted laws known as the Clarendon Code, designed to shore up the position of the re-established Church of England, Charles acquiesced to the Clarendon Code even though he favoured a policy of religious tolerance. The major foreign policy issue of his reign was the Second Anglo-Dutch War. In 1670, he entered into the treaty of Dover. Louis agreed to aid him in the Third Anglo-Dutch War and pay him a pension, Charles attempted to introduce religious freedom for Catholics and Protestant dissenters with his 1672 Royal Declaration of Indulgence, but the English Parliament forced him to withdraw it. In 1679, Titus Oatess revelations of a supposed Popish Plot sparked the Exclusion Crisis when it was revealed that Charless brother, the crisis saw the birth of the pro-exclusion Whig and anti-exclusion Tory parties. Charles sided with the Tories, and, following the discovery of the Rye House Plot to murder Charles and James in 1683, Charles dissolved the English Parliament in 1681, and ruled alone until his death on 6 February 1685. He was received into the Roman Catholic Church on his deathbed, Charless wife, Catherine of Braganza, bore no live children, but Charles acknowledged at least twelve illegitimate children by various mistresses. He was succeeded by his brother James, Charles II was born in St Jamess Palace on 29 May 1630. His parents were Charles I and Henrietta Maria, Charles was their second son and child. Their first son was born about a year before Charles but died within a day, England, Scotland and Ireland were respectively predominantly Anglican, Presbyterian and Roman Catholic. At birth, Charles automatically became Duke of Cornwall and Duke of Rothesay, at or around his eighth birthday, he was designated Prince of Wales, though he was never formally invested. During the 1640s, when Charles was still young, his father fought Parliamentary, by spring 1646, his father was losing the war, and Charles left England due to fears for his safety. Charles I surrendered into captivity in May 1646, at The Hague, Charles had a brief affair with Lucy Walter, who later falsely claimed that they had secretly married
18.
Christiaan Huygens
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Christiaan Huygens, FRS was a prominent Dutch mathematician and scientist. He is known particularly as an astronomer, physicist, probabilist and horologist, Huygens was a leading scientist of his time. His work included early telescopic studies of the rings of Saturn and the discovery of its moon Titan and he published major studies of mechanics and optics, and pioneered work on games of chance. Christiaan Huygens was born on 14 April 1629 in The Hague, into a rich and influential Dutch family, Christiaan was named after his paternal grandfather. His mother was Suzanna van Baerle and she died in 1637, shortly after the birth of Huygens sister. The couple had five children, Constantijn, Christiaan, Lodewijk, Philips, Constantijn Huygens was a diplomat and advisor to the House of Orange, and also a poet and musician. His friends included Galileo Galilei, Marin Mersenne and René Descartes, Huygens was educated at home until turning sixteen years old. He liked to play with miniatures of mills and other machines and his father gave him a liberal education, he studied languages and music, history and geography, mathematics, logic and rhetoric, but also dancing, fencing and horse riding. In 1644 Huygens had as his mathematical tutor Jan Jansz de Jonge Stampioen, Descartes was impressed by his skills in geometry. His father sent Huygens to study law and mathematics at the University of Leiden, Frans van Schooten was an academic at Leiden from 1646, and also a private tutor to Huygens and his elder brother, replacing Stampioen on the advice of Descartes. Van Schooten brought his mathematical education up to date, in introducing him to the work of Fermat on differential geometry. Constantijn Huygens was closely involved in the new College, which lasted only to 1669, Christiaan Huygens lived at the home of the jurist Johann Henryk Dauber, and had mathematics classes with the English lecturer John Pell. He completed his studies in August 1649 and he then had a stint as a diplomat on a mission with Henry, Duke of Nassau. It took him to Bentheim, then Flensburg and he took off for Denmark, visited Copenhagen and Helsingør, and hoped to cross the Øresund to visit Descartes in Stockholm. While his father Constantijn had wished his son Christiaan to be a diplomat, in political terms, the First Stadtholderless Period that began in 1650 meant that the House of Orange was not in power, removing Constantijns influence. Further, he realised that his son had no interest in such a career, Huygens generally wrote in French or Latin. While still a student at Leiden he began a correspondence with the intelligencer Mersenne. Mersenne wrote to Constantijn on his sons talent for mathematics, the letters show the early interests of Huygens in mathematics
19.
London
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London /ˈlʌndən/ is the capital and most populous city of England and the United Kingdom. Standing on the River Thames in the south east of the island of Great Britain and it was founded by the Romans, who named it Londinium. Londons ancient core, the City of London, largely retains its 1. 12-square-mile medieval boundaries. London is a global city in the arts, commerce, education, entertainment, fashion, finance, healthcare, media, professional services, research and development, tourism. It is crowned as the worlds largest financial centre and has the fifth- or sixth-largest metropolitan area GDP in the world, London is a world cultural capital. It is the worlds most-visited city as measured by international arrivals and has the worlds largest city airport system measured by passenger traffic, London is the worlds leading investment destination, hosting more international retailers and ultra high-net-worth individuals than any other city. Londons universities form the largest concentration of education institutes in Europe. In 2012, London became the first city to have hosted the modern Summer Olympic Games three times, London has a diverse range of people and cultures, and more than 300 languages are spoken in the region. Its estimated mid-2015 municipal population was 8,673,713, the largest of any city in the European Union, Londons urban area is the second most populous in the EU, after Paris, with 9,787,426 inhabitants at the 2011 census. The citys metropolitan area is the most populous in the EU with 13,879,757 inhabitants, the city-region therefore has a similar land area and population to that of the New York metropolitan area. London was the worlds most populous city from around 1831 to 1925, Other famous landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, St Pauls Cathedral, Tower Bridge, Trafalgar Square, and The Shard. The London Underground is the oldest underground railway network in the world, the etymology of London is uncertain. It is an ancient name, found in sources from the 2nd century and it is recorded c.121 as Londinium, which points to Romano-British origin, and hand-written Roman tablets recovered in the city originating from AD 65/70-80 include the word Londinio. The earliest attempted explanation, now disregarded, is attributed to Geoffrey of Monmouth in Historia Regum Britanniae and this had it that the name originated from a supposed King Lud, who had allegedly taken over the city and named it Kaerlud. From 1898, it was accepted that the name was of Celtic origin and meant place belonging to a man called *Londinos. The ultimate difficulty lies in reconciling the Latin form Londinium with the modern Welsh Llundain, which should demand a form *lōndinion, from earlier *loundiniom. The possibility cannot be ruled out that the Welsh name was borrowed back in from English at a later date, and thus cannot be used as a basis from which to reconstruct the original name. Until 1889, the name London officially applied only to the City of London, two recent discoveries indicate probable very early settlements near the Thames in the London area
20.
Edmond Halley
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Edmond Halley, FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of Halleys Comet. He was the second Astronomer Royal in Britain, succeeding John Flamsteed, Halley was born in Haggerston, in east London. His father, Edmond Halley Sr. came from a Derbyshire family and was a wealthy soap-maker in London, as a child, Halley was very interested in mathematics. He studied at St Pauls School, and from 1673 at The Queens College, while still an undergraduate, Halley published papers on the Solar System and sunspots. While at Oxford University, Halley was introduced to John Flamsteed, influenced by Flamsteeds project to compile a catalog of northern stars, Halley proposed to do the same for the Southern Hemisphere. In 1676, Halley visited the south Atlantic island of Saint Helena, while there he observed a transit of Mercury, and realised that a similar transit of Venus could be used to determine the absolute size of the Solar System. He returned to England in May 1678, in the following year he went to Danzig on behalf of the Royal Society to help resolve a dispute. Because astronomer Johannes Hevelius did not use a telescope, his observations had been questioned by Robert Hooke, Halley stayed with Hevelius and he observed and verified the quality of Hevelius observations. In 1679, Halley published the results from his observations on St. Helena as Catalogus Stellarum Australium which included details of 341 southern stars and these additions to contemporary star maps earned him comparison with Tycho Brahe, e. g. the southern Tycho as described by Flamsteed. Halley was awarded his M. A. degree at Oxford, in 1686, Halley published the second part of the results from his Helenian expedition, being a paper and chart on trade winds and monsoons. The symbols he used to represent trailing winds still exist in most modern day weather chart representations, in this article he identified solar heating as the cause of atmospheric motions. He also established the relationship between pressure and height above sea level. His charts were an important contribution to the field of information visualisation. Halley spent most of his time on lunar observations, but was interested in the problems of gravity. One problem that attracted his attention was the proof of Keplers laws of planetary motion, Halleys first calculations with comets were thereby for the orbit of comet Kirch, based on Flamsteeds observations in 1680-1. Although he was to calculate the orbit of the comet of 1682. They indicated a periodicity of 575 years, thus appearing in the years 531 and 1106 and it is now known to have an orbital period of circa 10,000 years. In 1691, Halley built a bell, a device in which the atmosphere was replenished by way of weighted barrels of air sent down from the surface
21.
Richard Towneley
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Richard Towneley was an English mathematician, natural philosopher and astronomer from Towneley near Burnley, Lancashire. He introduced John Flamsteed to the micrometer and invented the deadbeat escapement used in two clocks in the Greenwich Observatory, Towneley was born at Nocton, southeast of Lincoln in Lincolnshire, on 10 October 1629. His father was Charles Towneley and his mother before marriage was Mary Trappes and he had three brothers and three sisters. Towneley came from a Catholic family which stoutly refused to conform to the Protestant Church and he is thought to have been educated at one of the English colleges in the Low Countries as his younger brothers are both known to have studied at the English College, Douai in France. His interests included mathematics, natural philosophy and astronomy, Richard married Mary Paston of Barningham, Norfolk and fathered four sons and four daughters. Although the date of their marriage is not recorded their first son Clement, was born in 1654, by 1653 the Lancashire lands were regained, but the Nocton estate in Lincolnshire had to be sold in 1661 to pay outstanding debts. The income from the estate meant that Towneley had no need to take any other employment. He devoted himself to the study of mathematics and natural philosophy, henry Power, of Halifax, was both the Towneley familys physician and a friend who shared Towneleys enthusiasm for experimentation. On 27 April 1661, they used a barometer, of the type invented by Evangelista Torricelli in 1643, as a result, they recognised a relationship between the density of air and its pressure. Later in 1662, Boyle was able to publish what is now known as Boyles Law, Towneley published little of his own work but in May 1667 he sent a letter to the Royal Society touching the invention of dividing a foot into many thousand parts for mathematical purposes. Adrien Auzout had claimed a French first in inventing the micrometer, Towneley wrote to point out that Auzout was not the first person to have developed such a device as the English astronomer William Gascoigne had developed one before the Civil War. Towneley had produced a version of that micrometer and was using it in Lancashire. The Royal Society showed great interest in Towneleys micrometer and he sent them one made in Lancashire by one of his tenants, during the winter of 1664–5, the skies of the northern hemisphere were dominated by a brilliant comet, which was the most conspicuous since that of 1618. Accurate angular measurements were of importance to the astronomers of the time. His problem was solved in 1667, when he saw Richard Towneleys micrometer and this instrument used a pair of fine-pitched screws to move two pointers in the focal plane of a Keplerian telescope. Hooke published an engraving of the instrument to accompany Towneleys description in 1667 and its principle was to lie at the heart of astronomical measurement down to the twentieth century. This autograph manuscript was lot 128 in a sale of the Towneley familys manuscripts sold in 1883, according to Webster it is now in Yale University Library. Hookes first publication, in 1661, was a pamphlet on capillary action, in 1970, Derek Howse brought to more general attention a collection of some seventy letters written between 1673 and 1688 by the first Astronomer Royal, John Flamsteed, to Towneley
22.
Joseph-Nicolas Delisle
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Joseph-Nicolas Delisle was a French astronomer and cartographer. He was born in Paris, one of the 11 sons of Claude Delisle, like many of his brothers, among them Guillaume Delisle, he initially followed classical studies. Soon however, he moved to astronomy under the supervision of Joseph Lieutaud, in 1714 he entered the French Academy of Sciences as pupil of Giacomo Filippo Maraldi. Though he was a good scientist and member of a family he did not have much money. In 1712 he set up an observatory at the Luxembourg Palace, from 1719 to 1722 he was employed at the Royal observatory, before returning to his observatory at the Luxembourg Palace. In 1724 he met Edmond Halley in London and, among other things and his life changed radically in 1725 when he was called by the Russian czar Peter the Great to Saint Petersburg to create and run the school of astronomy. He arrived there only in 1726, after the death of the czar and he became quite rich and famous, to such an extent that when he returned to Paris in 1747, he built a new observatory in the palace of Cluny, later made famous by Charles Messier. Also he received the title of Astronomer from the Academy, in Russia he prepared the map of the known North Pacific that was used by Vitus Bering. He was elected a Fellow of the Royal Society in 1725, in 1760 he proposed that the international scientific community coordinate observations of the 1761 Transit of Venus in order to determine the absolute distance of the Earth from the Sun. He developed a map showing where on Earth this transit would be visible, actual implementation of these observational efforts were hindered by the Seven Years War. In 1763 he retired to the Abbey of St Genevieve, dying in Paris sometime in 1768, in 1740 Delisle undertook an expedition to Siberia with the object of observing from Beryozovo the transit of Mercury across the sun. An account of the expedition is given in Volume 72 of the LHistoire générale des voyages. Delisle and his party set out from St. Petersburg on 28 February 1740, arriving in Beryozovo, on the bank of the River Ob, on 9 April, having travelled via Moscow, the Volga, and Tyumen. On 22 April, the date of the transit of Mercury, the sun was obscured by clouds, however, Delisle arrived back in St. Petersburg on 29 December 1740, having sojourned in Tobolsk and Moscow en route. Throughout the expedition, Delisle recorded numerous ornithological, botanical, zoological, geographical and it seems that Delisle even planned to write a general study of the peoples of Siberia. On 30 June 1740, Delisle visited a monastery in Tobolsk, the plan for a map of the Russian Empire was launched by Peter the Great, but did not come to fruition until two decades later, in the reign of Empress Anna. Ivan Kirilov, the first director of the imperial Cartographic Office, had Delisle officially invited to Russia with a view to his collaborating on the map of the empire. Using his own methods, but consulting Delisle for expert advice, Kirilov published in 1734 a general map, the edition was abandoned after Kirilovs death in 1737
23.
Charles Green (astronomer)
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Born sometime in December 1734, Green was the youngest son of Joshua Green, a prosperous farmer who lived near Swinton in Yorkshire. His education, according to his future brother-in-law William Wales, was chiefly at a school near Denmark Street in Soho, following Bradleys death in 1762, Green continued in the role of assistant for Bradleys successor Nathaniel Bliss. Due to the ill-health of Bliss, much of the work of practical observational astronomy devolved upon Green at this time. On the voyage to Barbados, the pair were using their observations to determine the accuracy of the lunar distance method. A compromise was reached in which the monitoring of the Harrison mechanism was undertaken by Maskelyne, Greens return to England in the autumn of 1764 coincided with the death of Nathaniel Bliss, Green returned to Greenwich to continue Bliss work until the appointment of a new Astronomer Royal. The new Astronomer Royal proved to be Nevil Maskelyne, Green briefly served under him as assistant, but left Greenwich after a disagreement with his new superior. Although this is unmentioned in Waless short biography, Green is recorded as being the purser on the HMS Aurora in 1768, Green joined Cooks first voyage of circumnavigation in 1768, accompanied by a servant. Green was one of two official astronomers appointed by the Royal Society to observe the transit, the other was Cook himself, Green was to receive 200 guineas from the Society for the appointment. The expedition arrived at Tahiti, the site for the observation of the transit, on 11 April 1769. A camp was established and the equipment was in place by the start of May. Of paramount importance for Green was the calculation of a position of the location. The day of the transit, June 3, was a clear day, due to Greens death on the homeward voyage, the work of collating and analysing his results fell first to Cook, and ultimately to Nevil Maskelyne. Following the departure from Tahiti, the Endeavour continued south-westwards as Cook carried out his orders to explore the Southern Ocean. The expedition reached New Zealand in October 1769, giving Green an opportunity to observe the transit of Mercury from land, a landing was made at an inlet that would be subsequently called Mercury Bay on 3 November, the transit was successfully observed by Green on November 9. On reaching Australia, and during Cooks voyage along the coast, he named an island, Green Island, Green, by this time had contracted scurvy. The Endeavour was forced to make for Batavia for repairs, disease were rife in the Dutch-controlled city, including malaria and dysentery, Green contracted the latter, dying on 29 January 1771, twelve days after the ships departure from the port. Cook, in recording Greens death in his log, went on to add that Green had been in ill-health for some time and his lifestyle had contributed to his early death. Green married Elizabeth Long in March 1768 in London, the records of the Royal Society mention making a provision of £50 per annum for his wife for the duration of the expedition
24.
James Cook
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Captain James Cook FRS RN was a British explorer, navigator, cartographer, and captain in the Royal Navy. Cook joined the British merchant navy as a teenager and joined the Royal Navy in 1755 and he saw action in the Seven Years War, and subsequently surveyed and mapped much of the entrance to the Saint Lawrence River during the siege of Quebec. This helped bring Cook to the attention of the Admiralty and Royal Society, in three voyages Cook sailed thousands of miles across largely uncharted areas of the globe. He mapped lands from New Zealand to Hawaii in the Pacific Ocean in greater detail, as he progressed on his voyages of discovery he surveyed and named features, and recorded islands and coastlines on European maps for the first time. He displayed a combination of seamanship, superior surveying and cartographic skills, physical courage, Cook was attacked and killed while attempting to kidnap the native chief of Hawaii during his third exploratory voyage in the Pacific in 1779. He left a legacy of scientific and geographical knowledge which was to influence his successors well into the 20th century, and numerous memorials worldwide have been dedicated to him. James Cook was born on 7 November 1728 in the village of Marton in Yorkshire and baptised on 14 November in the church of St Cuthbert. He was the second of eight children of James Cook, a Scottish farm labourer from Ednam in Roxburghshire, in 1736, his family moved to Airey Holme farm at Great Ayton, where his fathers employer, Thomas Skottowe, paid for him to attend the local school. In 1741, after five years schooling, he work for his father. For leisure, he would climb a hill, Roseberry Topping, enjoying the opportunity for solitude. Cooks Cottage, his parents last home, which he is likely to have visited, is now in Melbourne, having moved from England and reassembled, brick by brick. In 1745, when he was 16, Cook moved 20 miles to the village of Staithes. Historians have speculated that this is where Cook first felt the lure of the sea while gazing out of the shop window. After 18 months, not proving suitable for work, Cook travelled to the nearby port town of Whitby to be introduced to friends of Sandersons, John. The Walkers, who were Quakers, were prominent local ship-owners in the coal trade and their house is now the Captain Cook Memorial Museum. Cook was taken on as a merchant navy apprentice in their fleet of vessels. His first assignment was aboard the collier Freelove, and he spent several years on this and various other coasters, sailing between the Tyne and London. As part of his apprenticeship, Cook applied himself to the study of algebra, geometry, trigonometry, navigation and his three-year apprenticeship completed, Cook began working on trading ships in the Baltic Sea
25.
Mercury Bay
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Mercury Bay is a large V-shaped bay on the eastern coast of the Coromandel Peninsula on the North Island of New Zealand. This bay was named by the English navigator Captain James Cook during his exploratory expeditions, by the Māori it was named Te-Whanganui-o-Hei, the great bay of Hei. On 9 November 1769, Cook landed on the shores of this bay to observe a Transit of Mercury. In 1919, an area of land around Shakespeare Cliff was set aside, but the actual site of Cooks landing and observation was the eastern end of Cooks Beach, near the Purangi estuary. A smaller memorial plinth was established there also, the mouth of Mercury Bay is ten kilometres across, and its coastline extends some 20 km. On the shore of this bay is the town of Whitianga. Several small islets are located at the southern and northern extremities of the bay, Mercury Bay is a great location for game fishing, with the Mercury Bay Game Fishing Club being one of the largest in New Zealand. With the nearby presence of the Te Whanganui-A-Hei Marine Reserve, large varieties of species can be found in the area, the bay is also widely known for its yachting. The Mercury Bay Boating Club in Whitianga was the club in New Zealands first challenge for the Americas Cup
26.
Capel Lofft
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Capel or Capell Lofft was an English lawyer, minor political figure and miscellaneous writer. Born in London, he was educated at Eton College, and Peterhouse, Cambridge and he was called to the bar in 1775, and the deaths of his father and uncle left him with a handsome property and the family estates. He became the patron of Robert Bloomfield, the author of The Farmers Boy, Lofft died at Montcalieri, near Turin. He married Anne, daughter of Henry Emlyn, in 1778 and their fourth son Capell Lofft the younger, also a writer, inherited his fathers liberal ideas and principles, and carried them in youth to greater extremes. In his old age he abandoned these theories, which had brought him into the company of some of the political agitators of the day. He died in America, where he had a Virginia estate and this article incorporates text from a publication now in the public domain, Chisholm, Hugh, ed. article name needed
27.
William Herschel
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Frederick William Herschel, KH, FRS was a British astronomer and composer of German origin, and brother of fellow astronomer Caroline Herschel, with whom he worked. Born in the Electorate of Hanover, Herschel followed his father into the Military Band of Hanover, Herschel constructed his first large telescope in 1774, after which he spent nine years carrying out sky surveys to investigate double stars. The resolving power of the Herschel telescopes revealed that the nebulae in the Messier catalogue were clusters of stars, Herschel published catalogues of nebulae in 1802 and in 1820. In the course of an observation on 13 March 1781, he realized that one celestial body he had observed was not a star and this was the first planet to be discovered since antiquity and Herschel became famous overnight. As a result of this discovery, George III appointed him Court Astronomer and he was elected as a Fellow of the Royal Society and grants were provided for the construction of new telescopes. Herschel pioneered the use of astronomical spectrophotometry as a tool, using prisms. Other work included a determination of the rotation period of Mars, the discovery that the Martian polar caps vary seasonally. In addition, Herschel discovered infrared radiation, Herschel was made a Knight of the Royal Guelphic Order in 1816. He was the first President of the Royal Astronomical Society when it was founded in 1820 and he died in August 1822, and his work was continued by his only son, John Herschel. Herschel was born in the Electorate of Hanover in Germany, then part of the Holy Roman Empire and his father was an oboist in the Hanover Military Band. In 1755 the Hanoverian Guards regiment, in whose band Wilhelm, at the time the crowns of Great Britain and Hanover were united under King George II. As the threat of war with France loomed, the Hanoverian Guards were recalled from England to defend Hanover, after they were defeated at the Battle of Hastenbeck, Herschels father Isaak sent his two sons to seek refuge in England in late 1757. Although his older brother Jakob had received his dismissal from the Hanoverian Guards, Wilhelm, nineteen years old at this time, was a quick student of the English language. In England he went by the English rendition of his name, in addition to the oboe, he played the violin and harpsichord and later the organ. He composed numerous works, including 24 symphonies and many concertos. Six of his symphonies were recorded in April 2002 by the London Mozart Players, Herschel moved to Sunderland in 1761 when Charles Avison immediately engaged him as first violin and soloist for his Newcastle orchestra, where he played for one season. In ‘Sunderland in the County of Durh, apprill 20th 1761’ he wrote his Symphony No.8 in C Minor. He was head of the Durham Militia band 1760–61 and visited the home of Sir Ralph Milbanke at Halnaby Hall in 1760, after Newcastle he moved to Leeds and Halifax where he was the first organist at St John the Baptist church
28.
NASA
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President Dwight D. Eisenhower established NASA in 1958 with a distinctly civilian orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29,1958, disestablishing NASAs predecessor, the new agency became operational on October 1,1958. Since that time, most US space exploration efforts have led by NASA, including the Apollo Moon landing missions, the Skylab space station. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the agency is also responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA shares data with various national and international such as from the Greenhouse Gases Observing Satellite. Since 2011, NASA has been criticized for low cost efficiency, from 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1. In the early 1950s, there was challenge to launch a satellite for the International Geophysical Year. An effort for this was the American Project Vanguard, after the Soviet launch of the worlds first artificial satellite on October 4,1957, the attention of the United States turned toward its own fledgling space efforts. This led to an agreement that a new federal agency based on NACA was needed to conduct all non-military activity in space. The Advanced Research Projects Agency was created in February 1958 to develop technology for military application. On July 29,1958, Eisenhower signed the National Aeronautics and Space Act, a NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA, earlier research efforts within the US Air Force and many of ARPAs early space programs were also transferred to NASA. In December 1958, NASA gained control of the Jet Propulsion Laboratory, NASA has conducted many manned and unmanned spaceflight programs throughout its history. Some missions include both manned and unmanned aspects, such as the Galileo probe, which was deployed by astronauts in Earth orbit before being sent unmanned to Jupiter, the experimental rocket-powered aircraft programs started by NACA were extended by NASA as support for manned spaceflight. This was followed by a space capsule program, and in turn by a two-man capsule program. This goal was met in 1969 by the Apollo program, however, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory, to date, NASA has launched a total of 166 manned space missions on rockets, and thirteen X-15 rocket flights above the USAF definition of spaceflight altitude,260,000 feet. The X-15 was an NACA experimental rocket-powered hypersonic research aircraft, developed in conjunction with the US Air Force, the design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems
29.
Astronomy Picture of the Day
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Astronomy Picture of the Day is a website provided by NASA and Michigan Technological University. According to the website, Each day a different image or photograph of our universe is featured, the photograph does not necessarily correspond to a celestial event on the exact day that it is displayed, and images are sometimes repeated. However, the pictures and descriptions often relate to current events in astronomy, the text has several hyperlinks to more pictures and websites for more information. Past images are stored in the APOD Archive, with the first image appearing on June 16,1995 and this initiative has received support from NASA, the National Science Foundation, and MTU. The images are sometimes authored by people or organizations outside NASA, when APOD began it received only 14 page views on its first day. As of 2012 it had received over a billion image views, APOD is also translated into 21 languages daily. APOD was presented at a meeting of the American Astronomical Society in 1996 and its practice of using hypertext was analyzed in a paper in 2000. It received a Scientific American Sci/Tech Web Award in 2001, in 2002, the website was featured in an interview with Nemiroff on CNN Saturday Morning News. In 2003, the two published a book titled The Universe,365 Days from Harry N. Abrams. APOD was the Featured Collection in the November 2004 issue of D-Lib Magazine, during the United States federal government shutdown of 2013, APOD continued its service on mirror sites. Dr. Robert J. Nemiroff and Dr. Jerry T
30.
Space Place at Carter Observatory
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Space Place at Carter Observatory stands at the top of the Botanic Gardens in Wellington, New Zealand. It re-opened in March 2010 following a NZ$5 million refurbishment, with a new exhibition and digital planetarium celebrating the culture, heritage, parliament established the Carter Observatory in 1937, it opened in 1941, following some delays caused by the beginnings of World War II. It is regarded as the observatory in Wellington, and was built on the site of a previous observatory nicknamed the Tin Shed. The observatory became a base for research in New Zealand. Research began with solar investigations and when new staff joined during the 1970s it expanded to variable stars, galaxies, comets, the observatory has had formal research programmes and assists amateur astronomers to perform their own research. The Carter Observatory became New Zealands National Observatory in 1977, in recent years, its role shifted from a focus on research to increasingly concentrate on public education about space. It is now one of four institutions run by Museums Wellington, in 2015 Museums Wellington rebranded the observatory to encourage accessibility, giving it the name ‘Space Place at Carter Observatory’. Space Place at Carter Observatory houses two main telescopes within its building and a third telescope nearby. The Thomas Cooke telescope, a historic 9 3⁄4-inch Cooke Refractor named after Thomas Cooke, the Ruth Crisp telescope, described below, arrived as a donation in the 1960s. Not far from its building, the Carter Observatory operates the Thomas King Observatory. The historic Dominion Observatory is also nearby, but is not operated by the Carter Observatory, once used for research at the Carter Observatorys outstation at Black Birch, in the South Island of New Zealand, it later moved to the main premises in Wellington. A grant from Pub Charity allowed improvements to the installation in December 2005, the Observatory had the dome motorised, efforts have commenced to start a research programme based around the facility, possibly involving deep-sky imaging, microlensing capability and photometry. The Carter Observatory also operates the nearby Thomas King Observatory, astronomers have maintained its 12.5 cm telescope in good condition throughout its nearly 125-year history. Last refurbished in May 2001, the Thomas King telescope served until recently for public viewing of the sun, the filter has since transferred to a telescope mounted to the side of the Thomas Cooke refractor in the main observatory building. Gifford Observatory, also located in Wellington Dominion Observatory, Wellington The Carter Observatorys main website Wellington City Council website
31.
International Standard Serial Number
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An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication. The ISSN is especially helpful in distinguishing between serials with the same title, ISSN are used in ordering, cataloging, interlibrary loans, and other practices in connection with serial literature. The ISSN system was first drafted as an International Organization for Standardization international standard in 1971, ISO subcommittee TC 46/SC9 is responsible for maintaining the standard. When a serial with the content is published in more than one media type. For example, many serials are published both in print and electronic media, the ISSN system refers to these types as print ISSN and electronic ISSN, respectively. The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers, as an integer number, it can be represented by the first seven digits. The last code digit, which may be 0-9 or an X, is a check digit. Formally, the form of the ISSN code can be expressed as follows, NNNN-NNNC where N is in the set, a digit character. The ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, for calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, the modulus 11 of the sum must be 0. There is an online ISSN checker that can validate an ISSN, ISSN codes are assigned by a network of ISSN National Centres, usually located at national libraries and coordinated by the ISSN International Centre based in Paris. The International Centre is an organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, at the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept, where ISBNs are assigned to individual books, an ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an identifier associated with a serial title. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change, separate ISSNs are needed for serials in different media. Thus, the print and electronic versions of a serial need separate ISSNs. Also, a CD-ROM version and a web version of a serial require different ISSNs since two different media are involved, however, the same ISSN can be used for different file formats of the same online serial
32.
Inferior and superior planets
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In the Solar System, a planet is said to be inferior with respect to another planet if its orbit lies inside the other planets orbit around the Sun. In this situation, the planet is said to be superior to the former. In the reference frame of the Earth, in which the terms were originally used, dwarf planets like Ceres or Pluto and most asteroids are superior in the sense that they almost all orbit outside the orbit of Earth. In the 16th century, the terms were modified by Copernicus, when Earth is stated or assumed to be the reference point, Inferior planet is used in reference to Mercury and Venus, which are closer to the Sun than the Earth is. Superior planet is used in reference to Mars, Jupiter, Saturn, the terms are sometimes used more generally, for example, the Earth is an inferior planet as seen from Mars. These terms are different from the inner planet and outer planet, which designate those planets which lie inside the asteroid belt. Inferior planet is different from minor planet or dwarf planet. Superior planet is different from gas giant
33.
Transit of Mercury from Mars
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A transit of Mercury across the Sun as seen from Mars takes place when the planet Mercury passes directly between the Sun and Mars, obscuring a small part of the Suns disc for an observer on Mars. During a transit, Mercury can be seen from Mars as a black disc moving across the face of the Sun. Transits of Mercury from Mars are roughly two more common than transits of Mercury from Earth, there are several per decade. No human has ever seen a transit of Mercury from Mars. The Mars rovers Spirit and Opportunity could have observed the transit of January 12,2005 and they were able to observe transits of Deimos across the Sun, but at 2 angular diameter, Deimos is about 20 times larger than Mercurys 6.1 angular diameter. The rover Curiosity observed the Mercury transit of June 3,2014, the Mercury-Mars synodic period is 100.888 days. It can be calculated using the formula 1/, where P is the period of Mercury. The inclination of Mercurys orbit with respect to that of Mars is 5. 16°, which is less than its value of 7. 00° with respect to Earths ecliptic. The simultaneous occurrence of a transit of Mercury and a transit of Venus is extremely rare, but somehow more frequent than from Earth, and will next occur in the years 18,713,19,536 and 20,029. On several occasions a related event is predicted, a transit of Mercury, on November 28,3867 there is a transit of Earth and Moon, and two days later a transit of Mercury occurs. On January 16,18551 transits of Mercury and Venus are separated by 14 hours, giorgini, J. D. Yeomans, D. K. Chamberlin, A. B. Chodas, P. W. Jacobson, R. A. JPLs On-Line Solar System Data Service, Bulletin of the American Astronomical Society 28,1158,1996, transits of Mercury on Mars - Fifteen millennium catalog,5000 BC -10000 AD JPL Horizons
34.
Transit of Earth from Mars
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A transit of Earth across the Sun as seen from Mars takes place when the planet Earth passes directly between the Sun and Mars, obscuring a small part of the Suns disc for an observer on Mars. During a transit, Earth would be visible from Mars as a black disc moving across the face of the Sun. They occur every 26,79 and 100 years, and every 1,000 years or so there is an extra 53rd-year transit. Transits of Earth from Mars usually occur in pairs, with one following the other after 79 years, rarely, there are three in the series. The transits also follow a 284-year cycle, occurring at intervals of 100.5,79,25.5, and 79 years, Transits occurring when Mars is at its ascending node are in May, those at descending node happen in November. This cycle corresponds fairly closely to 151 Mars orbits,284 Earth orbits, and 133 synodic periods, and is analogous to the cycle of transits of Venus from Earth, there are currently four such active series, containing from 8 to 25 transits. A new one is set to begin in 2394, the last series ending was in 1211. No one has seen a transit of Earth from Mars. The last such transit took place on May 11,1984, during the event, the Moon could almost always also be seen in transit, although due to the distance between Earth and Moon, sometimes one body completes the transit before the other begins. A transit of Earth from Mars corresponds to Mars being perfectly uniformly illuminated at opposition from Earth, during the 1879 event, this permitted Charles Augustus Young to attempt a careful measurement of the oblateness of Mars. He obtained the value 1/219, or 0.0046 and this is close to the modern value of 1/154. Much more recently, better measurements of the oblateness of Mars have been made by using radar from the Earth, a science fiction short story published in 1971 by Arthur C. Clarke, called Transit of Earth, depicts a doomed astronaut on Mars observing the transit in 1984 and this short story was first published in the January 1971 issue of Playboy magazine. Sometimes Earth only grazes the Sun during a transit, in this case it is possible that in some areas of Mars a full transit can be seen while in other regions there is only a partial transit. The last transit of this type was on 30 April 1211, and it is also possible that a transit of Earth can be seen in some parts of Mars as a partial transit, while in others Earth misses the Sun. Such a transit last occurred on 26 October 664, and the transit of this type will occur on 14 December 5934. The simultaneous occurrence of a transit of Venus and a transit of Earth is extremely rare, the Observatory,3,471 Meeus, Jean. SOLEX Transits of Earth on Mars – Fifteen millennium catalog,5000 BC –10000 AD JPL HORIZONS System Near miss of the Earth-moon system
35.
Atmosphere of Mercury
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Mercury has a very tenuous and highly variable atmosphere containing hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor, with a combined pressure level of about 10−14 bar. The exospheric species originate either from the Solar wind or from the planetary crust, Solar light pushes the atmospheric gases away from the Sun, creating a comet-like tail behind the planet. The existence of a Mercurian atmosphere had been contentious before 1974, although by that time a consensus had formed that Mercury, like the Moon and this conclusion was confirmed in 1974 when the unmanned Mariner 10 spaceprobe discovered only a tenuous exosphere. Later, in 2008, improved measurements were obtained by the MESSENGER spacecraft, the Mercurian exosphere consists of a variety of species originating either from the Solar wind or from the planetary crust. The first constituents discovered were atomic hydrogen, helium and atomic oxygen, the near-surface concentrations of these elements were estimated to vary from 230 cm−3 for hydrogen to 44,000 cm−3 for oxygen, with an intermediate concentration of helium. In 2008 the MESSENGER probe confirmed the presence of atomic hydrogen, Mercurys exospheric hydrogen and helium are believed to come from the Solar wind, while the oxygen is likely to be of crustal origin. The fourth species detected in Mercurys exosphere was sodium and it was discovered in 1985 by Drew Potter and Tom Morgan, who observed its Fraunhofer emission lines at 589 and 589.6 nm. The average column density of this element is about 1 ×1011 cm−2, sodium is observed to concentrate near the poles, forming bright spots. Its abundance is also enhanced near the dawn terminator as compared to the dusk terminator, some research has claimed a correlation of the sodium abundance with certain surface features such as Caloris or radio bright spots, however these results remain controversial. The properties and spatial distribution of two elements are otherwise very similar. In 1998 another element, calcium, was detected with column density three orders of magnitude below that of sodium, observations by the MESSENGER probe in 2009 showed that calcium is concentrated mainly near the equator—opposite to what is observed for sodium and potassium. In 2008 the MESSENGER probes Fast Imaging Plasma Spectrometer discovered several molecular and different ions in the vicinity of Mercury, including H2O+ and their abundances relative to sodium are about 0.2 and 0.7, respectively. Other ions such as H3O+, OH, O2+ and Si+ are present as well, the near-surface abundance of this newly detected constituent is roughly comparable to that of sodium. Mariner 10s ultraviolet observations have established an upper bound on the surface density at about 105 particles per cubic centimeter. This corresponds to a pressure of less than 10−14 bar. The temperature of the Mercurys exosphere depends on species as well as geographical location, for exospheric atomic hydrogen, the temperature appears to be about 420 K, a value obtained by both Mariner 10 and MESSENGER. The temperature for sodium is much higher, reaching 750–1500 K on the equator and 1, some observations show that Mercury is surrounded by a hot corona of calcium atoms with temperature between 12,000 and 20,000 K. Because of Mercurys proximity to the Sun, the pressure of light is much stronger than near Earth
36.
Mercury's magnetic field
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Mercurys magnetic field is approximately a magnetic dipole apparently global, on planet Mercury. Data from Mariner 10 led to its discovery in 1974, the spacecraft measured the strength as 1. 1% that of Earths magnetic field. The origin of the field can be explained by dynamo theory. The magnetic field is strong enough near the bow shock to slow the solar wind, the magnetic field is about 1. 1% as strong as Earths. At the Hermean equator, the strength of the magnetic field is around 300 nT. Mercurys magnetic field is weaker than Earths because its core had cooled and solidified more quickly than Earths, although Mercurys magnetic field is much weaker than Earths magnetic field, it is still strong enough to deflect the solar wind, inducing a magnetosphere. Whether the magnetic field changed to any significant degree between the Mariner 10 mission and the MESSENGER mission remains an open question, in addition they pointed out that estimates of the dipole obtained from bow shock and/or magnetopause positions range from approximately 200 nT-RM3 to approximately 400 nT-RM3. They concluded that the lack of agreement among models is due to limitations imposed by the spatial distribution of available observations. 2011, using high-quality MESSENGER data from many orbits around Mercury – as opposed to just a few high-speed flybys – found that the moment is 195 ±10 nT-RM3. The origins of the field can be explained by dynamo theory. Before the discovery of its field in 1974, it was thought that because of Mercury′s small size. There are still difficulties with this theory, including the fact that Mercury has a slow. This dynamo is probably weaker than Earths because it is driven by thermo-compositional convection associated with inner core solidification, because of the planets slow rotation, the resulting magnetic field is dominated by small-scale components that fluctuate quickly with time. Like Earths, Mercurys magnetic field is tilted, meaning that the poles are not located in the same area as the geographic poles. As a result of the asymmetry in Mercurys internal magnetic field. In particular, the polar cap where field lines are open to the interplanetary medium is much larger near the south pole. This geometry implies that the polar region is much more exposed than in the north to charged particles heated and accelerated by solar wind–magnetosphere interactions. The strength of the moment and the tilt of the dipole moment are completely unconstrained
37.
Bach quadrangle
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The Bach quadrangle encompasses the south polar part of Mercury poleward of latitude 65° S. About half of the region was beyond the terminator during the three Mariner 10 encounters and hence not visible and these combinations provided excellent qualitative control of topographic relief and a good quantitative photogrammetric base. However, sun-elevation angles of the images are limited to less than 25°, the imaged part of the Bach region covers about 1,570,000 km2. Its surface consists of craters of a variety of sizes and morphologies, as well as plains units, fault scarps. It includes three double-ring basins that range from 140 to 200 km in diameter, Bach, Cervantes, another large crater, Pushkin, is 240 km in diameter and occurs at the map boundary at latitude 65° S. longitude 25°. Both Bach and Bernini display extensive fields of secondary craters, an unusual area between lat 69° and 80° S. and long 30° and 60° consists of young, relatively smooth plains marked by many flat-topped ridges unlike any seen in other areas of Mercury. Scarps similar to Discovery Rupes are relatively common throughout the Bach region, the most common terrain units in the region are the plains units, which display a wide range of small-crater densities. During MESSENGERs January 14,2008 flyby, the probe photographed previously unseen portions of this region, superposition relations among craters and basins, and their ejecta, provide the best means of establishing the relative time-stratigraphic order of crater and basin materials. These attributes of the crater population allow stratigraphic sequences to be constructed over large regions. To the extent that changes are systematic with increasing age. On the basis of this evaluation, five crater ages are defined and used to make stratigraphic assignments. However, the low sun angle at which images in the region were acquired may make craters appear younger than in parts of Mercury where images were taken at higher sun angles. Of the region’s three double-ring basins, Bach and Bernini are moderately fresh and have well-defined secondary-crater fields, whereas Cervantes is degraded, the inner rings of the three basins are about half the diameter of the outer rings. Bach’s inner ring, the most complete, is only to the southeast. The area within it and part of the area between it and the ring are filled with smooth plains material. The inner rings of Cervantes and Bernini consist of discontinuous, low, rounded hills, Bernini has a small central peak. As a consequence, continuous and discontinuous ejecta are mapped together in the Bach region as “radial facies. ”With this exception, therefore, all of the craters within the Bach region are probably the result of impact by meteorites, small planetesimals, and possibly comets. About 60 percent of the area consists of tracts of planar surfaces having a variety of small-scale textures
38.
Beethoven quadrangle
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The Beethoven quadrangle is located in the equatorial region of Mercury, in the center of the area imaged by Mariner 10. Most pictures of the quadrangle were obtained at high sun angles as the Mariner 10 spacecraft receded from the planet, generally, topography appears highly subdued because of the sun angle, and boundaries between map units are not clearly defined. Impact craters larger than about 250 km are referred to as basins, unlike many basins on the Moon, however, the two obvious basins in the quadrangle, Beethoven and Raphael, are not multiringed, whereas well-developed rings encircle many craters of lesser diameters. Remnant ejecta blankets around parts of the Beethoven and Raphael basins are subdued in appearance, however, where they can be recognized, these extensive aprons allow a generalized regional stratigraphic sequence to be determined. A third basin, extremely subdued but probable, is centered at latitude 0°, Mariner 10 images in the northeastern part of the quadrangle are very poor to unusable. This area therefore contains blank patches or only a few crater outlines, another difficulty in mapping is the poor match in topographic bases between Beethoven and adjacent quadrangles. Mismatches are especially common along the borders with the Kuiper and Discovery quadrangles to the east and southeast, major divisions of rock units in the quadrangle are plains materials and crater and basin materials. Plains materials are identified in part by surface texture and their relative ages determined by density of superposed craters, intercrater plains material, one of the two oldest plains units, was originally described by Trask and Guest. It covers large areas in the western, central, and southeastern parts of the quadrangle, there, as in other regions of Mercury, its surface reveals the outlines of many buried crater rim crests and knobby remnants of an older resurfaced terra. This unit has been scoured by many secondary craters that have formed overlapping chains, the unit appears to be gradational laterally eastward with plains and terra material, undivided, and vertically with intermediate plains material. The intercrater plains material is probably about the age as the ejecta blanket around Beethoven basin. That the plains unit is younger than Beethoven may be indicated in some areas where the basin’s ejecta blanket appears to be obscured by the overlap or embayment of plains material. Spudis and Prosser have suggested that Beethoven may possibly be late c3 in age or as old as early c2, the plains and terra unit, occurring in the central and eastern parts of the quadrangle, was originally mapped to the east in the Kuiper quadrangle. The term was applied where differences in image quality prevent clear distinctions between plains and terra materials. The name was adopted in the Beethoven quadrangle for the same reason, the unit intergrades to the west and south with intercrater plains material and is interpreted to be of the same origin and composition. The intermediate plains material and smooth plains material probably also consist of mixtures of relatively fine crater ejecta, both units are thicker than the intercrater plains unit. The intermediate plains material is widespread in areas in the west half of the quadrangle and fills floors of older craters. Smooth plains material, the youngest plains unit, occurs as scattered patches in low areas and covers the floors of craters of c4 age
39.
Borealis quadrangle
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The Borealis quadrangle is a quadrangle on Mercury surrounding the north pole down to 65° latitude. The west half of the area is dominated by older craters. Younger crater materials, intermediate plains material, and small patches of plains material are superposed on all other units. The crater Verdi,122 km in diameter, is the largest of the younger craters and its extensive ejecta blanket and secondary crater field are superposed on plains materials and older craters. The east half of the area is characterized by smooth plains material. This unit covers vast expanses of Borealis Planitia, a depression about 1,000 km in diameter that has an irregular arcuate west boundary and this depression is located over the site of one or several old impact structures. Most of the used for geologic mapping were acquired by the departing spacecraft during the first pass. The Mercury II encounter provided no usable images of the map area, no stereoscopic photographic pairs are available for the Borealis region. Because the terminator was a few degrees away from the 0°-180° meridian at the time of the first encounter, photographs of the region were acquired under a wide range of lighting conditions. Mercurys equatorial plane is inclined less than 2° to its orbital plane, the resulting lag and orbital eccentricity create a variation of mean temperature not only with latitude, as on the Earth, but also with longitude. Further, conservation of angular momentum and spin-orbit coupling cause considerable variation in the length of daylight. Despite these considerations and despite the range in surface temperatures of several hundred kelvins. Within the Borealis region, three widespread plains units are recognized largely by their obvious differences in density, which is closely related to relative age. From most heavily cratered to least cratered, these units are intercrater plains material, intermediate plains material, visual identification is confirmed and refined by actual crater counts. The curve for the uplands was derived from crater counts in the region northwest of crater Tsiolkovskiy. The curve for the part of Oceanus Procellarum was obtained in an area centered near lat 2°00 N. Material of Borealis Planitia was not included in the smooth plains count because images of the area were blurred by spacecraft motion, and so reliable crater counts could not be obtained. However, smooth plains south of lat 65° N. in the Shakespeare quadrangle, in the crater Strindberg, the plains materials that lie outside Borealis Planitia are distributed in irregular belts, which are subparallel to the terminator and to one another
40.
Derain quadrangle
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The Derain quadrangle is one of fifteen quadrangles on Mercury. It runs from 288 to 360° longitude and from -25 to 25° latitude, named after the Derain crater, it was mapped in detail for the first time after MESSENGER entered orbit around Mercury in 2011. It had not been mapped prior to that point because it was one of the six quadrangles that was not illuminated when Mariner 10 made its flybys in 1974 and 1975. These six quadrangles continued to be known by their albedo feature names, the massive Skinakas Basin overlaps the border of this quadrangle and neighboring Eminescu quadrangle
41.
Discovery quadrangle
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The Discovery quadrangle lies within the heavily cratered part of Mercury in a region roughly antipodal to the 1550-km-wide Caloris Basin. Interspersed with the craters and basins both in space and time are plains deposits that are probably of several different origins, because of its small size and very early segregation into core and crust, Mercury has seemingly been a dead planet for a long time—possibly longer than the Moon. Its geologic history, therefore, records with considerable clarity some of the earliest and most violent events took place in the inner Solar System. As on the Moon and Mars, sequences of craters and basins of differing relative ages provide the best means of establishing stratigraphic order on Mercury, overlap relations among many large mercurian craters and basins are clearer than those on the Moon. Therefore, we can build up many local stratigraphic columns involving both crater or basin materials and nearby plains materials. Over all of Mercury, the crispness of crater rims and the morphology of their walls, central peaks, ejecta deposits, the youngest craters or basins in a local stratigraphic sequence have the sharpest, crispest appearance. The oldest craters consist only of shallow depressions with raised, rounded rims. On this basis, five age categories of craters and basins have been mapped, tracts of plains materials range in size from a few kilometers across to intercrater areas several hundred kilometers in width. This material is not all of the same origin. Strom and others and Trask and Strom cited evidence that large areas of plains are of volcanic origin. Smaller tracts are more apt to be impact melt, loose debris pooled in low spots by seismic shaking, the origin of many individual tracts must necessarily remain uncertain without additional information. Plains materials have been grouped into four units on the basis of both the density of super-posed craters and the relation of each unit to adjacent crater and basin materials and these units are listed as follows from oldest to youngest. Contacts between intercrater plains and intermediate plains units that occur outside mapped craters and basins are gradational, smooth plains material occurs in relatively small patches throughout the quadrangle on the floors of c4 and older craters and basins and in tracts between craters. More bright-halo craters occur on this unit than on either the inter-crater plains or intermediate plains units, very smooth plains material occurs on the floors of some of the youngest craters. In summary, a history of contemporaneous formation of craters, basins. The Discovery quadrangle includes some of the most distinctive relief-forming material on the planet, the unit consists of a jumble of evenly spaced hills and valleys about equal in size. The hilly and lineated unit and the enclosed hummocky plains unit appear to be relatively young, in addition, they lie almost directly opposite that basin on the planet. Morphologically diverse scarps, ridges, troughs, and other structural lineaments are relatively common in the Discovery quadrangle, Dzurisin documented a well-developed pattern of linear lithospheric fractures in the quadrangle that predate the period of heavy bombardment
