1.
Perseids
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The Perseids /ˈpərsiːɪdz/ are a prolific meteor shower associated with the comet Swift–Tuttle. The Perseids are so called because the point from which appear to come, called the radiant. The name derives in part from the word Perseides, a found in Greek mythology referring to the sons of Perseus. The stream of debris is called the Perseid cloud and stretches along the orbit of the comet Swift–Tuttle, the cloud consists of particles ejected by the comet as it travels on its 133-year orbit. Most of the particles have been part of the cloud for around a thousand years, however, there is also a relatively young filament of dust in the stream that was pulled off the comet in 1865, which can give an early mini-peak the day before the maximum shower. The shower is visible from each year, with the peak in activity between 9 and 14 August, depending on the particular location of the stream. During the peak, the rate of meteors reaches 60 or more per hour and they can be seen all across the sky, however, because of the shower’s radiant in the constellation of Perseus, the Perseids are primarily visible in the Northern Hemisphere. While many meteors arrive between dawn and noon, they are not visible due to daylight. Some can also be seen before midnight, often grazing the Earth’s atmosphere to produce long bright trails, most Perseids burn up in the atmosphere while at heights above 80 kilometres. Some Catholics refer to the Perseids as the tears of Saint Lawrence, suspended in the sky but returning to once a year on August 10. In 1835, Adolphe Quetelet identified the shower as emanating from the constellation Perseus, in 1866, after the perihelion passage of Swift-Tuttle in 1862, the Italian astronomer Giovanni Virginio Schiaparelli discovered the link between meteor showers and comets. The finding is contained in an exchange of letters with Angelo Secchi
2.
Hobby
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A hobby is a regular activity that is done for enjoyment, typically during ones leisure time. Hobbies can include collecting themed items and objects, engaging in creative and artistic pursuits, playing sports, a list of hobbies is lengthy and always changing as interests and fashions change. By continually participating in a hobby, one can acquire substantial skill. Engagement in hobbies has increased since the nineteenth century as workers have more leisure time and advancing production. As some hobbies have become popular, like stamp collecting, others have been created following technological advances. Hobbyists are a part of a group of people engaged in leisure pursuits where the boundaries of each group overlap to some extent. The Serious Leisure Perspective groups hobbyists with amateurs and volunteers and identifies three broad groups of activity with hobbies being found mainly in the Serious leisure category. Casual leisure is intrinsically rewarding, short-lived, pleasurable activity requiring little or no preparation b, Serious leisure is the systematic pursuit of an amateur, hobbyist, or volunteer that is substantial, rewarding and results in a sense of accomplishment. Project-based leisure is a short-term often a one-off project that is rewarding, in the 16th century, the term hobyn had the meaning of small horse and pony. The term hobby horse was documented in a 1557 payment confirmation for a Hobbyhorse from Reading, the item, originally called a Tourney Horse, was made of a wooden or basketwork frame with an artificial tail and head. It was designed for a child to mimic riding a real horse, by 1816 the derivative, hobby, was introduced into the vocabulary of a number of English people. Over the course of subsequent centuries, the term came to be associated with recreation, a hobby became an activity that is practised regularly and usually with some worthwhile purpose. Hobbies are usually, but not always, practised primarily for interest and enjoyment, the origins pursuits that others thought somewhat childish or trivial. However, as early as 1676 Sir Matthew Hale, in Contemplations Moral and Divine and he was acknowledging that a hobby horse produces a legitimate sense of pride. By the mid 18th century there was a flourishing of hobbies as working people had more hours of work. They spent more time to pursue interests that brought them satisfaction, however, there was concern that these working people might not use their leisure time in worthwhile pursuits. The hope of weaning people away from bad habits by the provision of counter-attractions came to the fore in the 1830s, the flourishing book and magazine trade of the day encouraged worthwhile hobbies and pursuits. The burgeoning manufacturing trade made materials used in hobbies cheap and was responsive to the interests of hobbyists
3.
Sky
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The sky is everything that lies above the surface of the Earth, including the atmosphere and outer space. In the field of astronomy, the sky is called the celestial sphere. This is viewed from Earths surface as a dome where the Sun, stars, planets. The celestial sphere is divided into regions called constellations. Usually, the sky is used informally as the point of view from the Earths surface, however. In some cases, such as in discussing the weather, the sky refers to only the lower, during daylight, the sky appears to be blue because air scatters blue sunlight more than it scatters red. At night, the sky appears to be a dark surface or region scattered with stars. During the day, the Sun can be seen in the sky obscured by clouds. In the night sky the Moon, planets and stars are visible in the sky, some of the natural phenomena seen in the sky are clouds, rainbows, and aurorae. Lightning and precipitation can also be seen in the sky during storms, birds, insects, aircraft, and kites are often considered to fly in the sky. Due to human activities, smog during the day and light pollution during the night are often seen above large cities. Except for light that directly from the sun, most of the light in the day sky is caused by scattering. The scattering due to molecule sized particles is greater in the forward and backward directions than it is in the lateral direction. Scattering is significant for light at all visible wavelengths but is stronger at the end of the visible spectrum, meaning that the scattered light is bluer than its source. The remaining sunlight, having lost some of its wavelength components. Scattering also occurs more strongly in clouds. Individual water droplets exposed to light will create a set of colored rings. If a cloud is thick enough, scattering from water droplets will wash out the set of colored rings
4.
Naked eye
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Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered naked, in astronomy, the naked eye may be used to observe events that can be viewed without equipment, such as an astronomical conjunction, the passage of a comet, or a meteor shower. Sky lore and various tests demonstrate a wealth of phenomena that can be seen with the unaided eye. The basic accuracies of the eye are, Quick autofocus from distances of 25 cm to 50 cm to infinity. Angular resolution, about 1 arcminute, approximately 0. 02° or 0.0003 radians, field of view, simultaneous visual perception in an area of about 160° × 175°. Faint stars up to +8 magnitude under a dark sky. Photometry to ±10% or 1% of intensity – in a range between night and day of 1,10,000,000,000, symmetries of 10–20, see the measurements of Tycho Brahe and the Egyptians. Even a few hundred kilometers away from an area where the sky can appear to be very dark. For most people, these are likely to be the best observing conditions within their reach, under such typical dark sky conditions, the naked eye can see stars with an apparent magnitude up to +6m. Under perfect dark sky conditions where all light pollution is absent, the angular resolution of the naked eye is about 1′, however, some people have sharper vision than that. There is anecdotal evidence that people had seen the Galilean moons of Jupiter before telescopes were invented, Uranus, when discovered in 1781, was the first planet discovered using technology rather than being spotted by the naked eye. In practice, the extinction and dust reduces this number somewhat. In the center of a city, where the limiting magnitude due to extreme amounts of light pollution can be +4m or less. Colors can be seen but this is limited by the fact that the eye uses rods instead of cones to view fainter stars, the visibility of diffuse objects such as star clusters and galaxies is much more strongly affected by light pollution than is that of planets and stars. Under typical dark conditions only a few objects are visible. The Triangulum Galaxy is a difficult averted vision object and only visible at all if it is higher than 50° in the sky, the globular clusters M3 in Canes Venatici and M92 in Hercules are also visible with the naked eye under such conditions. Under really dark sky conditions, however, M33 is easy to see, many other Messier objects are also visible under such conditions. The most distant objects that have seen by the naked eye are nearby bright galaxies such as Centaurus A, Bodes Galaxy, Sculptor Galaxy
5.
Binoculars
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Binoculars or field glasses are two telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes when viewing distant objects. Most are sized to be held using both hands, although sizes vary widely from opera glasses to large pedestal mounted military models. Almost from the invention of the telescope in the 17th century the advantages of mounting two of them side by side for binocular vision seems to have been explored, most early binoculars used Galilean optics, that is, they used a convex objective and a concave eyepiece lens. The Galilean design has the advantage of presenting an image but has a narrow field of view and is not capable of very high magnification. This type of construction is used in very cheap models. They also have large exit pupils making centering less critical and the field of view works well in those applications. These are typically mounted on a frame or custom-fit onto eyeglasses. An improved image and higher magnification is achieved in binoculars employing Keplerian optics, since the Keplerian configuration produces an inverted image, different methods were used to turn the image right way up. In aprismatic binoculars with Keplerian optics each tube has one or two additional lenses between the objective and the ocular and these lenses are used to erect the image. The binoculars with erecting lenses have a disadvantage, their length is too long. Such binoculars were popular in the 1800s, but became obsolete shortly after the Karl Zeiss company introduced improved prism binoculars in the 1890s, Optical prisms added to the design are another way to turn the image right way up, usually in a Porro prism or roof-prisms design. Porro prism binoculars are named after Italian optician Ignazio Porro who patented this image erecting system in 1854, Binoculars of this type use a Porro prism in a double prism Z-shaped configuration to erect the image. This feature results in binoculars that are wide, with lenses that are well separated. Thus, the size of binoculars is reduced, Binoculars using roof prisms may have appeared as early as the 1870s in a design by Achille Victor Emile Daubresse. Most roof prism binoculars use either the Abbe-Koenig prism or the Schmidt-Pechan prism designs to erect the image and they have objective lenses that are approximately in line with the eyepieces. Roof-prisms designs create an instrument that is narrower and more compact than Porro prisms, there is also a difference in image brightness. Roof-prisms designs also require tighter tolerances for alignment of their optical elements and this adds to their expense since the design requires them to use fixed elements that need to be set at a high degree of collimation at the factory. Porro prisms binoculars occasionally need their prism sets to be re-aligned to bring them into collimation, the fixed alignment in roof-prism designs means the binoculars normally will not need re-collimation
6.
Telescope
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A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation. The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s and they found use in both terrestrial applications and astronomy. Within a few decades, the telescope was invented, which used mirrors to collect. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s, the word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors. The word telescope was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galileis instruments presented at a banquet at the Accademia dei Lincei, in the Starry Messenger, Galileo had used the term perspicillum. The earliest recorded working telescopes were the telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals, Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, Galileo heard about the Dutch telescope in June 1609, built his own within a month, and improved upon the design in the following year. Also in 1609, Thomas Harriot became the first person known to point a telescope skyward in order to make observations of a celestial object. The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors—reduction of spherical aberration and no chromatic aberration—led to many proposed designs, in 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name, the Newtonian reflector. The invention of the lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter. The largest reflecting telescopes currently have objectives larger than 10 m, the 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays. The first purpose built radio telescope went into operation in 1937, since then, a tremendous variety of complex astronomical instruments have been developed. The name telescope covers a range of instruments. Most detect electromagnetic radiation, but there are differences in how astronomers must go about collecting light in different frequency bands. The near-infrared can be collected much like light, however in the far-infrared and submillimetre range. For example, the James Clerk Maxwell Telescope observes from wavelengths from 3 μm to 2000 μm, on the other hand, the Spitzer Space Telescope, observing from about 3 μm to 180 μm uses a mirror. Also using reflecting optics, the Hubble Space Telescope with Wide Field Camera 3 can observe in the range from about 0.2 μm to 1.7 μm
7.
Research
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It is used to establish or confirm facts, reaffirm the results of previous work, solve new or existing problems, support theorems, or develop new theories. A research project may also be an expansion on past work in the field, to test the validity of instruments, procedures, or experiments, research may replicate elements of prior projects or the project as a whole. The primary purposes of research are documentation, discovery, interpretation, or the research and development of methods. Approaches to research depend on epistemologies, which vary considerably both within and between humanities and sciences, there are several forms of research, scientific, humanities, artistic, economic, social, business, marketing, practitioner research, life, technological, etc. The earliest recorded use of the term was in 1577, Research has been defined in a number of different ways. Another definition of research is given by John W. Creswell and it consists of three steps, pose a question, collect data to answer the question, and present an answer to the question. Original research is research that is not exclusively based on a summary and this material is of a primary source character. The purpose of the research is to produce new knowledge. Original research can take a number of forms, depending on the discipline it pertains to, in analytical work, there are typically some new mathematical results produced, or a new way of approaching an existing problem. The degree of originality of the research is among major criteria for articles to be published in academic journals, graduate students are commonly required to perform original research as part of a dissertation. Scientific research is a way of gathering data and harnessing curiosity. This research provides scientific information and theories for the explanation of the nature, scientific research is funded by public authorities, by charitable organizations and by private groups, including many companies. Scientific research can be subdivided into different classifications according to their academic, Research in the humanities involves different methods such as for example hermeneutics and semiotics. Humanities scholars usually do not search for the correct answer to a question. Context is always important, and context can be social, historical, political, cultural, an example of research in the humanities is historical research, which is embodied in historical method. Historians use primary sources and other evidence to systematically investigate a topic, other studies aim to merely examine the occurrence of behaviours in societies and communities, without particularly looking for reasons or motivations to explain these. These studies may be qualitative or quantitative, and can use a variety of approaches, Artistic research, also seen as practice-based research, can take form when creative works are considered both the research and the object of research itself. It is the body of thought which offers an alternative to purely scientific methods in research in its search for knowledge
8.
Variable star
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A variable star is a star whose brightness as seen from Earth fluctuates. Many, possibly most, stars have at least some variation in luminosity, an ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol. This discovery, combined with supernovae observed in 1572 and 1604, proved that the sky was not eternally invariable as Aristotle. In this way, the discovery of variable stars contributed to the revolution of the sixteenth. The second variable star to be described was the eclipsing variable Algol, by Geminiano Montanari in 1669, chi Cygni was identified in 1686 by G. Kirch, then R Hydrae in 1704 by G. D. Maraldi. By 1786 ten variable stars were known, John Goodricke himself discovered Delta Cephei and Beta Lyrae. Since 1850 the number of variable stars has increased rapidly, especially after 1890 when it became possible to identify variable stars by means of photography. The latest edition of the General Catalogue of Variable Stars lists more than 46,000 variable stars in the Milky Way, as well as 10,000 in other galaxies, and over 10,000 suspected variables. The most common kinds of variability involve changes in brightness, but other types of variability also occur, by combining light curve data with observed spectral changes, astronomers are often able to explain why a particular star is variable. Variable stars are generally analysed using photometry, spectrophotometry and spectroscopy, measurements of their changes in brightness can be plotted to produce light curves. Peak brightnesses in the curve are known as maxima, while troughs are known as minima. By estimating the magnitude and noting the time of observation a visual lightcurve can be constructed. The American Association of Variable Star Observers collects such observations from participants around the world, from the light curve the following data are derived, are the brightness variations periodical, semiperiodical, irregular, or unique. What is the period of the brightness fluctuations, what is the shape of the light curve. From the spectrum the following data are derived, what kind of star is it, what is its temperature, is it a single star, or a binary. does the spectrum change with time. In very few cases it is possible to make pictures of a stellar disk and these may show darker spots on its surface. Combining light curves with spectral data often gives a clue as to the changes occur in a variable star. For example, evidence for a star is found in its shifting spectrum because its surface periodically moves toward and away from us
9.
Double star
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In observational astronomy, a double star or visual double is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. Multiple stars are studied in this way, although the dynamics of multiple stellar systems are more complex than those of binary stars. There are three types of paired stars, Optical Doubles are unrelated stars that appear close together through chance alignment with Earth, visual Binaries are gravitationally-bound stars that are separately visible with a telescope. Non-Visual Binaries are stars whose binary status was deduced through more esoteric means, such as occultation, spectroscopy, improvements in telescopes can shift previously non-visual binaries into visual binaries, as happened with Polaris A in 2006. It is only the inability to observe two separate stars that distinguish non-visual and visual binaries. Mizar, in Ursa Major, was observed to be double by Benedetto Castelli, since that time, the search has been carried out thoroughly and the entire sky has been examined for double stars down to a limiting apparent magnitude of about 9.0. At least 1 in 18 stars brighter than 9.0 magnitude in the half of the sky are known to be double stars visible with a 36-inch telescope. The unrelated categories of optical doubles and true binaries are lumped together for historical and practical reasons, when Mizar was found to be a binary, it was quite difficult to determine whether a double star was a binary system or only an optical double. Improved telescopes, spectroscopy, and photography are the tools used to make the distinction. After it was determined to be a binary, Mizars components were found to be spectroscopic binaries themselves. Observation of visual double stars by visual measurement will yield the separation, or angular distance, the position angle specifies the direction in which the stars are separated and is defined as the bearing from the brighter component to the fainter, where north is 0°. In the measures of a binary, the position angle will change progressively. Plotting the measures in the plane will produce an ellipse and this is the apparent orbit, the projection of the orbit of the two stars onto the celestial sphere, the true orbit can be computed from it. Although it is expected that the majority of catalogued visual doubles are visual binaries, visual double stars may be distinguished from binary stars by observing their relative motion. Some bright visual double stars have a Bayer designation, in this case, the components may be denoted by superscripts. An example of this is α Crucis, whose components are α1 Crucis, since α1 Crucis is a spectroscopic binary, this is actually a multiple star. Superscripts are also used to more distant, physically unrelated, pairs of stars with the same Bayer designation, such as α1,2 Capricorni, ξ1,2 Centauri. These optical pairs are resolvable by the naked eye, apart from these pairs, the components of a double star are generally denoted by the letters A and B appended to the designation, of whatever sort, of the double star
10.
Occultation
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An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy and it can also refer to any situation wherein an object in the foreground blocks from view an object in the background. In this general sense, occultation applies to the visual scene observed from low-flying aircraft wherein foreground objects obscure distant objects dynamically, as the scene changes over time. The term occultation is most frequently used to describe those relatively frequent occasions when the Moon passes in front of a star during the course of its orbital motion around the Earth. Events that take place on the Moons dark limb are of particular interest to observers, the Moons orbit is inclined to the ecliptic, and any stars with an ecliptic latitude of less than about 6.5 degrees may be occulted by it. There are three first magnitude stars that are close to the ecliptic that they may be occulted by the Moon and by planets – Regulus, Spica. Occultations of Aldebaran are presently only possible by the Moon, because the planets pass Aldebaran to the north, neither planetary nor lunar occultations of Pollux are currently possible. However, in the far future, occultations of Pollux will be possible, some deep-sky objects, such as the Pleiades, can also be occulted by the Moon. From an observational and scientific standpoint, these grazes are the most dynamic, the accurate timing of lunar occultations is performed regularly by astronomers. Lunar occultations timed to an accuracy of a few tenths of a second have various scientific uses, photoelectric analysis of lunar occultations have also discovered some stars to be very close visual or spectroscopic binaries. Some angular diameters of stars have been measured by timing of lunar occultations, several times during the year, someone on Earth can usually observe the Moon occulting a planet. Since planets, unlike stars, have significant angular sizes, lunar occultations of planets will create a zone on Earth from which a partial occultation of the planet will occur. An observer located within that narrow zone could observe the planets disk partly blocked by the moving moon. The same mechanic can be seen with the Sun, where observers on Earth will view it as a Solar Eclipse, therefore, a Total Solar Eclipse is effectively the same event as the Moon occulting the Sun. Stars may also be occulted by planets, uranuss rings were first discovered when that planet occulted a star in 1977. On 3 July 1989, Saturn passed in front of the 5th magnitude star 28 Sagittarii, pluto occulted stars in 1988,2002, and 2006, allowing its tenuous atmosphere to be studied via atmospheric limb sounding. In rare cases, one planet can pass in front of another, if the nearer planet appears larger than the more distant one, the event is called a mutual planetary occultation. An asteroid occultation occurs when an asteroid passes in front of a star, several events occur nearly every day over the world
11.
Star
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A star is a luminous sphere of plasma held together by its own gravity. The nearest star to Earth is the Sun, many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. However, most of the stars in the Universe, including all stars outside our galaxy, indeed, most are invisible from Earth even through the most powerful telescopes. Almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the stars lifetime, near the end of its life, a star can also contain degenerate matter. Astronomers can determine the mass, age, metallicity, and many properties of a star by observing its motion through space, its luminosity. The total mass of a star is the factor that determines its evolution. Other characteristics of a star, including diameter and temperature, change over its life, while the environment affects its rotation. A plot of the temperature of stars against their luminosities produces a plot known as a Hertzsprung–Russell diagram. Plotting a particular star on that allows the age and evolutionary state of that star to be determined. A stars life begins with the collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium. When the stellar core is sufficiently dense, hydrogen becomes steadily converted into helium through nuclear fusion, the remainder of the stars interior carries energy away from the core through a combination of radiative and convective heat transfer processes. The stars internal pressure prevents it from collapsing further under its own gravity, a star with mass greater than 0.4 times the Suns will expand to become a red giant when the hydrogen fuel in its core is exhausted. In some cases, it will fuse heavier elements at the core or in shells around the core, as the star expands it throws a part of its mass, enriched with those heavier elements, into the interstellar environment, to be recycled later as new stars. Meanwhile, the core becomes a remnant, a white dwarf. Binary and multi-star systems consist of two or more stars that are bound and generally move around each other in stable orbits. When two such stars have a close orbit, their gravitational interaction can have a significant impact on their evolution. Stars can form part of a much larger gravitationally bound structure, historically, stars have been important to civilizations throughout the world
12.
Moon
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The Moon is an astronomical body that orbits planet Earth, being Earths only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, following Jupiters satellite Io, the Moon is second-densest satellite among those whose densities are known. The average distance of the Moon from the Earth is 384,400 km, the Moon is thought to have formed about 4.51 billion years ago, not long after Earth. It is the second-brightest regularly visible celestial object in Earths sky, after the Sun and its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art. The Moons gravitational influence produces the ocean tides, body tides, and this matching of apparent visual size will not continue in the far future. The Moons linear distance from Earth is currently increasing at a rate of 3.82 ±0.07 centimetres per year, since the Apollo 17 mission in 1972, the Moon has been visited only by uncrewed spacecraft. The usual English proper name for Earths natural satellite is the Moon, the noun moon is derived from moone, which developed from mone, which is derived from Old English mōna, which ultimately stems from Proto-Germanic *mǣnōn, like all Germanic language cognates. Occasionally, the name Luna is used, in literature, especially science fiction, Luna is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon. The principal modern English adjective pertaining to the Moon is lunar, a less common adjective is selenic, derived from the Ancient Greek Selene, from which is derived the prefix seleno-. Both the Greek Selene and the Roman goddess Diana were alternatively called Cynthia, the names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric. The name Diana is connected to dies meaning day, several mechanisms have been proposed for the Moons formation 4.51 billion years ago, and some 60 million years after the origin of the Solar System. These hypotheses also cannot account for the angular momentum of the Earth–Moon system. This hypothesis, although not perfect, perhaps best explains the evidence, eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists, You have eighteen months. Go back to your Apollo data, go back to computer, do whatever you have to. Dont come to our conference unless you have something to say about the Moons birth, at the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most popular. Afterward there were only two groups, the giant impact camp and the agnostics. Giant impacts are thought to have been common in the early Solar System, computer simulations of a giant impact have produced results that are consistent with the mass of the lunar core and the present angular momentum of the Earth–Moon system
13.
Asteroid
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Asteroids are minor planets, especially those of the inner Solar System. The larger ones have also been called planetoids and these terms have historically been applied to any astronomical object orbiting the Sun that did not show the disc of a planet and was not observed to have the characteristics of an active comet. As minor planets in the outer Solar System were discovered and found to have volatile-based surfaces that resemble those of comets, in this article, the term asteroid refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There are millions of asteroids, many thought to be the remnants of planetesimals. The large majority of known asteroids orbit in the belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects, individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups, C-type, M-type, and S-type. These were named after and are identified with carbon-rich, metallic. The size of asteroids varies greatly, some reaching as much as 1000 km across, asteroids are differentiated from comets and meteoroids. In the case of comets, the difference is one of composition, while asteroids are composed of mineral and rock, comets are composed of dust. In addition, asteroids formed closer to the sun, preventing the development of the aforementioned cometary ice, the difference between asteroids and meteoroids is mainly one of size, meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials, only one asteroid,4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye, and this only in very dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be visible to the eye for a short time. As of March 2016, the Minor Planet Center had data on more than 1.3 million objects in the inner and outer Solar System, the United Nations declared June 30 as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, the first asteroid to be discovered, Ceres, was found in 1801 by Giuseppe Piazzi, and was originally considered to be a new planet. In the early half of the nineteenth century, the terms asteroid. Asteroid discovery methods have improved over the past two centuries. This task required that hand-drawn sky charts be prepared for all stars in the band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would, hopefully, the expected motion of the missing planet was about 30 seconds of arc per hour, readily discernible by observers
14.
Comet
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A comet is an icy small Solar System body that, when passing close to the Sun, warms and begins to evolve gasses, a process called outgassing. This produces an atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of collections of ice, dust. The coma may be up to 15 times the Earths diameter, if sufficiently bright, a comet may be seen from the Earth without the aid of a telescope and may subtend an arc of 30° across the sky. Comets have been observed and recorded since ancient times by many cultures, Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars, hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition, Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma and the tail, however, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System, the discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets. As of November 2014 there are 5,253 known comets, however, this represents only a tiny fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System is estimated to be one trillion. Roughly one comet per year is visible to the eye, though many of those are faint. Particularly bright examples are called Great Comets, the word comet derives from the Old English cometa from the Latin comēta or comētēs. That, in turn, is a latinisation of the Greek κομήτης, Κομήτης was derived from κομᾶν, which was itself derived from κόμη and was used to mean the tail of a comet. The astronomical symbol for comets is ☄, consisting of a disc with three hairlike extensions. The solid, core structure of a comet is known as the nucleus, cometary nuclei are composed of an amalgamation of rock, dust, water ice, and frozen gases such as carbon dioxide, carbon monoxide, methane, and ammonia. As such, they are described as dirty snowballs after Fred Whipples model
15.
Nova
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A nova or classical nova is an astronomical event that causes the sudden appearance of a bright new star, that slowly fades from view over several weeks or many months. Novae should not be confused with more energetic astronomical phenomena known as supernovae. Several main sub-classes of novae exist, based on their many different scenarios, being classical novae, recurrent novae, dwarf novae and they are together under a group of variable stars collectively known as cataclysmic variable stars, which share some common properties as close binary systems. Classical novae eruptions are the most common type of novae and they are likely created in a close binary star system consisting of a white dwarf and either a main sequence, sub-giant or red giant star. This mostly hydrogen atmosphere is heated from the hot white dwarf star, which eventually reaches a critical temperature. A few novae produce short-lived nova remnants, lasting several centuries. Recurrent nova processes are the same as the classical nova, except that the ignition can be repeated because the companion star can again feed the dense atmosphere of the white dwarf. Occurrences of novae mostly occur in the sky along the path of the Milky Way, however, it is also quite possible for them to appear anywhere in the sky. They are far more frequent than galactic supernovae, presently averaging about ten per year, the majority are found telescopically, with few reaching naked-eye visibility, perhaps averaging about once every year to eighteen months. Novae reaching 1st or 2nd magnitude occur only several times per century, the last bright nova was V1369 Centauri reaching 3.3 magnitude on 14 December 2013. During the 16th century, astronomer Tycho Brahe observed the supernova SN1572 in the constellation Cassiopeia and he described it in his book De nova stella, giving rise to the name nova. In this work he argued that an object should be seen to move relative to the fixed stars. Though this was a supernova and not a nova, the terms were considered interchangeable until the 1930s, after this, novae were classified as classical novae to distinguishing them from supernovae, as their causes and energies were though to be different based soley in the observational evidence. Evolution of potential novae begins with two main stars in a binary system. One of the two evolves into a red giant leaving its remnant white dwarf core in orbit with the remaining star, the second star—which may be either a main sequence star or an aging giant—begins to shed its envelope onto its white dwarf companion when it overflows its Roche lobe. As a result, the white dwarf captures matter in an accretion disk steadily from the outer atmosphere. As the white dwarf consists of matter, so the accreted hydrogen does not inflate. Rapid, an all at once, uncontrolled fusion occurs when the temperature of this layer reaches ~20 million Kelvins
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Supernova
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This causes the sudden appearance of a new bright star, before slowly fading from sight over several weeks or months. Supernovae are more energetic than novae, in Latin, nova means new, referring astronomically to what appears to be a temporary new bright star. Adding the prefix super- distinguishes supernovae from ordinary novae, which are far less luminous, the word supernova was coined by Walter Baade and Fritz Zwicky in 1931. It is pronounced /ˌsuːpərnoʊvə/ with the plural supernovae /ˌsuːpərnoʊviː/ or supernovas, only three Milky Way naked-eye supernova events have been observed during the last thousand years, though many have been seen in other galaxies using telescopes. The most recent directly observed supernova in the Milky Way was Keplers Supernova in 1604, Supernovae may expel much, if not all, of the material away from a star, at velocities up to 30,000 km/s or 10% of the speed of light. This drives an expanding and fast-moving shock wave into the interstellar medium, and in turn, sweeping up an expanding shell of gas and dust. Supernovae create, fuse and eject the bulk of the chemical elements produced by nucleosynthesis, Supernovae play a significant role in enriching the interstellar medium with the heavier atomic mass chemical elements. Furthermore, the shock waves from supernovae can trigger the formation of new stars. Supernova remnants are expected to accelerate a large fraction of primary cosmic rays. They are also potentially strong galactic sources of gravitational waves, in the second case, the core of a massive star may undergo sudden gravitational collapse, releasing gravitational potential energy as a supernova. While some observed supernovae are more complex than these two simplified theories, the astrophysical collapse mechanics have been established and accepted by most astronomers for some time, in Latin, Nova means new, referring astronomically to what appears to be a temporary new bright star. Adding the prefix super- distinguishes supernovae from ordinary novae, which are far less luminous, the word supernova was coined by Walter Baade and Fritz Zwicky in 1931. It is pronounced /ˌsuːpərnoʊvə/ with the plural supernovae /ˌsuːpərnoʊviː/ or supernovas, the earliest recorded supernova, SN185, was viewed by Chinese astronomers in 185 AD. The brightest recorded supernova was SN1006, which occurred in 1006 AD and was described in detail by Chinese, the widely observed supernova SN1054 produced the Crab Nebula. Johannes Kepler began observing SN1604 at its peak on October 17,1604 and it was the second supernova to be observed in a generation. There is some evidence that the youngest galactic supernova, G1. 9+0.3, occurred in the late 19th century, neither supernova was noted at the time. In the case of G1. 9+0.3, high extinction along the plane of the galaxy could have dimmed the event sufficiently to go unnoticed, the situation for Cassiopeia A is less clear. Infrared light echos have been detected showing that it was a type IIb supernova and was not in a region of especially high extinction, before the development of the telescope, there have only been five supernovae seen in the last millennium
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Galaxy
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A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek galaxias, literally milky, Galaxies range in size from dwarfs with just a few billion stars to giants with one hundred trillion stars, each orbiting its galaxys center of mass. Galaxies are categorized according to their morphology as elliptical, spiral. Many galaxies are thought to have holes at their active centers. The Milky Ways central black hole, known as Sagittarius A*, has a four million times greater than the Sun. Recent estimates of the number of galaxies in the observable universe range from 200 billion to 2 trillion or more, most of the galaxies are 1,000 to 100,000 parsecs in diameter and separated by distances on the order of millions of parsecs. The space between galaxies is filled with a gas having an average density of less than one atom per cubic meter. The majority of galaxies are organized into groups, clusters. At the largest scale, these associations are generally arranged into sheets and filaments surrounded by immense voids. In Greek mythology, Zeus places his son born by a mortal woman, the infant Heracles, on Heras breast while she is asleep so that the baby will drink her divine milk and will thus become immortal. Hera wakes up while breastfeeding and then realizes she is nursing a baby, she pushes the baby away, some of her milk spills and. In the astronomical literature, the capitalized word Galaxy is often used to refer to our galaxy, the Milky Way, to distinguish it from the other galaxies in our universe. The English term Milky Way can be traced back to a story by Chaucer c. 1380, See yonder, lo, the Galaxyë Which men clepeth the Milky Wey, For hit is whyt. However, the word Universe was later understood to mean the entirety of existence, so this expression fell into disuse and the objects instead became known as galaxies. Tens of thousands of galaxies have been catalogued, but only a few have well-established names, such as the Andromeda Galaxy, the Magellanic Clouds, the Whirlpool Galaxy, and the Sombrero Galaxy. Astronomers work with numbers from certain catalogues, such as the Messier catalogue, the NGC, the IC, the CGCG, all of the well-known galaxies appear in one or more of these catalogues but each time under a different number. For example, Messier 109 is a galaxy having the number 109 in the catalogue of Messier, but also codes NGC3992, UGC6937, CGCG 269-023, MCG +09-20-044. One of the arguments to do so is that these impressive objects deserve better than uninspired codes, for instance, Bodifee and Berger propose the informal, descriptive name Callimorphus Ursae Majoris for the well-formed barred galaxy Messier 109 in Ursa Major
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Income
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Income is the consumption and savings opportunity gained by an entity within a specified timeframe, which is generally expressed in monetary terms. However, for households and individuals, income is the sum of all the wages, salaries, profits, interests payments, rents, in a given period of time. In the field of economics, the term may refer to the accumulation of both monetary and non-monetary consumption ability, with the former being used as a proxy for total income. Income per capita has been increasing steadily in almost every country, many factors contribute to people having a higher income such as education, globalisation and favorable political circumstances such as economic freedom and peace. Increase in income tends to lead to people choosing to work less hours. Developed countries have higher incomes as opposed to developing countries tending to have lower incomes, from labor services, as well as ownership of land and capital. In consumer theory income is another name for the budget constraint, the basic equation for this is Y = P x ⋅ x + P y ⋅ y This equation implies two things. First buying one unit of good x implies buying P x P y less units of good y. So, P x P y is the price of a unit of x as to the number of units given up in y. Second, if the price of x falls for a fixed Y, the usual hypothesis is that the quantity demanded of x would increase at the lower price, the law of demand. The generalization to more than two goods consists of modelling y as a composite good, the theoretical generalization to more than one period is a multi-period wealth and income constraint. For example, the person can gain more productive skills or acquire more productive income-earning assets to earn a higher income. In the multi-period case, something might happen to the economy beyond the control of the individual to reduce the flow of income. Changing measured income and its relation to consumption over time might be modeled accordingly, full income refers to the accumulation of both the monetary and the non-monetary consumption-ability of any given entity, such as a person or a household. According to what the economist Nicholas Barr describes as the definition of income, income may be defined as the. Sum of the value of rights exercised in consumption and the change in the value of the store of property rights. Since the consumption potential of non-monetary goods, such as leisure, cannot be measured, as such, however, it is criticized for being unreliable, i. e. failing to accurately reflect affluence of any given agent. It omits the utility a person may derive from non-monetary income and, on a macroeconomic level, according to Barr, in practice money income as a proportion of total income varies widely and unsystematically
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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
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Solar eclipse
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As seen from the Earth, a solar eclipse is a type of eclipse that occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks the Sun. This can happen only at new moon when the Sun and the Moon are in conjunction as seen from Earth in an alignment referred to as syzygy, in a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured, if the Moon were in a perfectly circular orbit, a little closer to the Earth, and in the same orbital plane, there would be total solar eclipses every month. However, the Moons orbit is inclined at more than 5 degrees to the Earths orbit around the Sun, Earths orbit is called the ecliptic plane as the Moons orbit must cross this plane in order for an eclipse to occur. In addition, the Moons actual orbit is elliptical, often taking it far away from Earth that its apparent size is not large enough to block the Sun totally. The orbital planes cross each other at a line of nodes resulting in at least two, and up to five, solar eclipses occurring each year, no more than two of which can be total eclipses. However, total solar eclipses are rare at any particular location because totality exists only along a path on the Earths surface traced by the Moons shadow or umbra. An eclipse is a natural phenomenon, nevertheless, in some ancient and modern cultures, solar eclipses have been attributed to supernatural causes or regarded as bad omens. A total solar eclipse can be frightening to people who are unaware of its explanation, as the Sun seems to disappear during the day. People referred to as eclipse chasers or umbraphiles will travel to locations to observe or witness predicted central solar eclipses. For the date of the next eclipse see the section Recent, during any one eclipse, totality occurs at best only in a narrow track on the surface of Earth. An annular eclipse occurs when the Sun and Moon are exactly in line with the Earth, hence the Sun appears as a very bright ring, or annulus, surrounding the dark disk of the Moon. A hybrid eclipse shifts between a total and annular eclipse, at certain points on the surface of Earth, it appears as a total eclipse, whereas at other points it appears as annular. A partial eclipse occurs when the Sun and Moon are not exactly in line with the Earth and this phenomenon can usually be seen from a large part of the Earth outside of the track of an annular or total eclipse. However, some eclipses can only be seen as an eclipse, because the umbra passes above the Earths polar regions. Partial eclipses are virtually unnoticeable in terms of the suns brightness, even at 99%, it would be no darker than civil twilight. Of course, partial eclipses can be observed if one is viewing the sun through a darkening filter, the Suns distance from Earth is about 400 times the Moons distance, and the Suns diameter is about 400 times the Moons diameter. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size, about 0.5 degree of arc in angular measure
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Optical telescope
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The larger the objective, the more light the telescope collects and the finer detail it resolves. People use telescopes and binoculars for activities such as astronomy, ornithology, pilotage and reconnaissance. The telescope is more a discovery of optical craftsmen than an invention of a scientist and it is in the Netherlands in 1608 where the first recorded optical telescopes appeared. The invention is credited to the spectacle makers Hans Lippershey and Zacharias Janssen in Middelburg, galileo greatly improved on these designs the following year, and is generally credited as the first to use a telescope for astronomy. Galileos telescope used Hans Lippersheys design of an objective lens and a concave eye lens. Johannes Kepler proposed an improvement on the design used a convex eyepiece. For reflecting telescopes, which use a mirror in place of the objective lens. The theoretical basis for curved mirrors behaving similar to lenses was probably established by Alhazen, the late 20th century has seen the development of adaptive optics and space telescopes to overcome the problems of astronomical seeing. The basic scheme is that the primary light-gathering element the objective and this image may be recorded or viewed through an eyepiece, which acts like a magnifying glass. The eye then sees an inverted magnified virtual image of the object, most telescope designs produce an inverted image at the focal plane, these are referred to as inverting telescopes. In fact, the image is both turned upside down and reversed left to right, so that altogether it is rotated by 180 degrees from the object orientation, in astronomical telescopes the rotated view is normally not corrected, since it does not affect how the telescope is used. However, a diagonal is often used to place the eyepiece in a more convenient viewing location, and in that case the image is erect. In terrestrial telescopes such as spotting scopes, monoculars and binoculars, There are telescope designs that do not present an inverted image such as the Galilean refractor and the Gregorian reflector. These are referred to as erecting telescopes, many types of telescope fold or divert the optical path with secondary or tertiary mirrors. These may be part of the optical design, or may simply be used to place the eyepiece or detector at a more convenient position. Telescope designs may also use specially designed additional lenses or mirrors to improve image quality over a field of view. Design specifications relate to the characteristics of the telescope and how it performs optically, several properties of the specifications may change with the equipment or accessories used with the telescope, such as Barlow lenses, star diagonals and eyepieces. These interchangeable accessories dont alter the specifications of the telescope, however they alter the way the telescopes properties function, typically magnification, angular resolution and FOV
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Observatory
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An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geology, oceanography and volcanology are examples of disciplines for which observatories have been constructed, historically, observatories were as simple as containing an astronomical sextant or Stonehenge. Astronomical observatories are mainly divided into four categories, space based, airborne, ground based, ground-based observatories, located on the surface of Earth, are used to make observations in the radio and visible light portions of the electromagnetic spectrum. Most optical telescopes are housed within a dome or similar structure, Telescope domes have a slit or other opening in the roof that can be opened during observing, and closed when the telescope is not in use. In most cases, the upper portion of the telescope dome can be rotated to allow the instrument to observe different sections of the night sky. Radio telescopes usually do not have domes, for optical telescopes, most ground-based observatories are located far from major centers of population, to avoid the effects of light pollution. The ideal locations for modern observatories are sites that have dark skies, a percentage of clear nights per year, dry air. At high elevations, the Earths atmosphere is thinner, thereby minimizing the effects of atmospheric turbulence, sites that meet the above criteria for modern observatories include the southwestern United States, Hawaii, Canary Islands, the Andes, and high mountains in Mexico such as Sierra Negra. Major optical observatories include Mauna Kea Observatory and Kitt Peak National Observatory in the USA, Roque de los Muchachos Observatory in Spain, and Paranal Observatory in Chile. Specific research study performed in 2009 shows that the best possible location for ground-based observatory on Earth is Ridge A — a place in the part of Eastern Antarctica. This location provides the least atmospheric disturbances and best visibility, beginning in 1930s, radio telescopes have been built for use in the field of radio astronomy to observe the Universe in the radio portion of the electromagnetic spectrum. Since the mid-20th century, a number of observatories have been constructed at very high altitudes, above 4. The largest and most notable of these is the Mauna Kea Observatory, the Chacaltaya Astrophysical Observatory in Bolivia, at 5,230 m, was the worlds highest permanent astronomical observatory from the time of its construction during the 1940s until 2009. It has now surpassed by the new University of Tokyo Atacama Observatory. As a result, the resolution of space telescopes such as the Hubble Space Telescope is often much smaller than a ground-based telescope with a similar aperture. However, all these advantages do come with a price, Space telescopes are much more expensive to build than ground-based telescopes. Due to their location, space telescopes are also difficult to maintain. The Hubble Space Telescope was serviced by the Space Shuttle while many other space telescopes cannot be serviced at all, Airborne observatories have the advantage of height over ground installations, putting them above most of the Earths atmosphere
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Astronomical society
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A list of notable groups devoted to promoting astronomy research and education. Airdrie Astronomical Association Amateur Astronomers Association of Pittsburgh American Association of Variable Star Observers, American Astronomical Society American Meteor Society, an amateur organization specializing in meteor observations. Association of Lunar and Planetary Observers, an amateur organization Astronomical League, Astronomical Society of Australia, the professional body representing astronomers in Australia. Astronomical Society of Glasgow Astronomical Society of India Astronomical Society of New South Wales, based in Sydney, Astronomical Society of South Australia Astronomical Society of Southern Africa Astronomical Society of the Pacific Astronomical Society of Victoria, based in Melbourne, Australia. Astronomical Society Ruđer Bošković, from Belgrade, Serbia Astronomische Gesellschaft Astronomy Centre, One of the UKs largest facilities for amateur observation, Birmingham Astronomical Society, in Birmingham, Alabama British Astronomical Association, the senior national association of amateur astronomers in the UK. EAAE - European Association for Astronomy Education, a European Association that promotes activities for schools, teachers, federation of Astronomical Societies International Meteor Organization, an international organization dealing in meteor observations. Network for Astronomy School Education - NASE a Program Group of IAU that works on Training Teachers Nibiru Sociedad Astronomica, Mexico City, sutherland Astronomical Society based in the southern suburbs of Sydney, Australia. Spaceturk, an organization specializing in planetary, lunar
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Phenomenon
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A phenomenon is any thing which manifests itself. Phenomena are often, but not always, understood as things that appear or experiences for a sentient being, the term came into its modern philosophical usage through Immanuel Kant, who contrasted it with the noumenon. In contrast to a phenomenon, a noumenon can not be directly observed, Kant was heavily influenced by Gottfried Wilhelm Leibniz in this part of his philosophy, in which phenomenon and noumenon serve as interrelated technical terms. In modern philosophical use, the phenomena has come to mean what is experienced is the basis of reality. He wrote that humans could infer only as much as their senses allowed, thus, the term phenomenon refers to any incident deserving of inquiry and investigation, especially events that are particularly unusual or of distinctive importance. According to The Columbia Encyclopedia, Modern philosophers have used phenomenon to designate what is apprehended before judgment is applied and this may not be possible if observation is theory laden. In scientific usage, a phenomenon is any event that is observable, however common it might be, even if it requires the use of instrumentation to observe, record, another example of scientific phenomena can be found in the experience of phantom limb sensations. This occurrence, the sensation of feeling in amputated limbs, is reported by over 70% of amputees, although the limb is no longer present, they report still experiencing sensations. This is an event that defies typical logic and has been a source of much curiosity within the medical and physiological fields. A mechanical phenomenon is a phenomenon associated with the equilibrium or motion of objects. Some examples are Newtons cradle, engines, and double pendulums, in gemology, a phenomenon is an unusual optical effect that is displayed by a gem. Play-of-color, labradorescence, iridescence, adularescence, chatoyancy, asterism, aventurescence, lustre, group phenomena concern the behavior of a particular group of individual entities, usually organisms and most especially people. The behavior of individuals often changes in a setting in various ways. Social phenomena apply especially to organisms and people in that states are implicit in the term. Attitudes and events particular to a group may have effects beyond the group, in popular usage, a phenomenon often refers to an extraordinary event. The term is most commonly used to refer to occurrences that at first defy explanation or baffle the observer
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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
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Meteor shower
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A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of debris called meteoroids entering Earths atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller than a grain of sand, so almost all of them disintegrate, intense or unusual meteor showers are known as meteor outbursts and meteor storms, which may produce greater than 1000 meteors an hour. The Meteor Data Centre lists about 600 suspected meteor showers of which about 100 are well established, the first great storm in modern times was the Leonids of November 1833. American Denison Olmsted explained the event most accurately, after spending the last weeks of 1833 collecting information he presented his findings in January 1834 to the American Journal of Science and Arts, published in January–April 1834, and January 1836. Work continued, however, coming to understand the nature of showers though the occurrences of storms perplexed researchers. In the 1890s, Irish astronomer George Johnstone Stoney and British astronomer Arthur Matthew Weld Downing, were the first to attempt to calculate the position of the dust at Earths orbit. They studied the dust ejected in 1866 by comet 55P/Tempel-Tuttle in advance of the anticipated Leonid shower return of 1898 and 1899, Meteor storms were anticipated, but the final calculations showed that most of the dust would be far inside of Earths orbit. The same results were independently arrived at by Adolf Berberich of the Königliches Astronomisches Rechen Institut in Berlin, although the absence of meteor storms that season confirmed the calculations, the advance of much better computing tools was needed to arrive at reliable predictions. In 1981 Donald K. Yeomans of the Jet Propulsion Laboratory reviewed the history of showers for the Leonids. A graph from it was adapted and re-published in Sky and Telescope and it showed relative positions of the Earth and Tempel-Tuttle and marks where Earth encountered dense dust. In 1985, E. D. Kondrateva and E. A. Reznikov of Kazan State University first correctly identified the years when dust was released which was responsible for several past Leonid meteor storms, in 1995, Peter Jenniskens predicted the 1995 Alpha Monocerotids outburst from dust trails. In anticipation of the 1999 Leonid storm, Robert H. McNaught, David Asher, in 2006 Jenniskens has published predictions for future dust trail encounters covering the next 50 years. Jérémie Vaubaillon continues to update predictions based on each year for the Institut de Mécanique Céleste et de Calcul des Éphémérides. Because meteor shower particles are all traveling in parallel paths, and at the same velocity and this radiant point is caused by the effect of perspective, similar to parallel railroad tracks converging at a single vanishing point on the horizon when viewed from the middle of the tracks. Meteor showers are almost always named after the constellation from which the appear to originate. This fixed point slowly moves across the sky during the due to the Earth turning on its axis. The radiant also moves slightly from night to night against the stars due to the Earth moving in its orbit around the sun
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Deep-sky object
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Deep-sky objects are astronomical objects other than individual stars and Solar System objects. The classification is used for the most part by amateur astronomers to denote visually observed faint naked eye and telescopic objects such as clusters, nebulae. Classifying non-stellar astronomical objects began soon after the invention of the telescope, as telescopes improved these faint nebulae would be broken into more descriptive scientific classifications such as interstellar clouds, star clusters, and galaxies. Deep-sky object, as a classification for these objects, has its origins in the modern field of amateur astronomy. There are many amateur astronomical techniques and activities associated with deep-sky objects, some of these objects are bright enough to find and see in binoculars and small telescopes. But the faintest objects need the power of telescopes with large objectives. Observing faint objects needs dark skies, so these relatively portable types of telescopes also lend themselves to the majority of amateurs who need to travel outside light polluted urban locations. To cut down light pollution and enhance contrast observers employ nebular filters designed to admit certain wavelength, there are organized activities associated with DSOs such as the Messier marathon which occurs at a specific time each year and involve observers trying to spot all 110 Messier objects in one night. Since the Messier catalog objects were discovered with relatively small 18th century telescopes it is a popular list with observers, a much more demanding test known as the Herschel 400 is designed to tax larger telescopes and experienced amateur astronomers. There are many astronomical object types that come under the description of deep-sky objects, Jess K. Gilmour, The practical astronomers deep-sky companion. W. H. Finlay, Concise Catalog of Deep-sky Objects, Astrophysical Information for 500 Galaxies, Clusters, includes the Messier objects, Herschel 400 & more. Roger Nelson Clark, Visual astronomy of the deep sky, burnhams Celestial Handbook by Robert Burnham, Jr. Deep Sky Observers Guide by Neil Bone, Wil Tirion, the practical astronomers deep-sky companion by Jess K. Gilmour. Concise Catalog of Deep-sky Objects, Astrophysical Information for 500 Galaxies, Clusters, includes the Messier objects, Herschel 400 & more Visual astronomy of the deep sky by Roger Nelson Clark
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Star cluster
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Star clusters or star clouds are groups of stars. Star clusters visible to the eye include Pleiades, Hyades. Globular clusters, or GC, are roughly spherical groupings of from 10,000 to several million stars packed into regions of from 10 to 30 light years across. They commonly consist of very old Population II stars—just a few hundred years younger than the universe itself—which are mostly yellow and red. Such stars predominate within clusters because hotter and more stars have exploded as supernovae. Yet a few rare blue stars exist in globulars, thought to be formed by mergers in their dense inner regions. In our galaxy, globular clusters are distributed roughly spherically in the halo, around the galactic centre. Super star clusters, such as Westerlund 1 in the Milky Way, may be the precursors of globular clusters. Our galaxy has about 150 globular clusters, some of which may have captured from small galaxies disrupted by the Milky Way. Some galaxies are much richer in globulars, the giant elliptical galaxy M87 contains over a thousand. A few of the brightest globular clusters are visible to the eye, with the brightest, Omega Centauri, having been known since antiquity. The best known globular cluster in the northern hemisphere is M13, in 2005, astronomers discovered a completely new type of star cluster in the Andromeda Galaxy, which is, in several ways, very similar to globular clusters. Currently, there are not any intermediate clusters discovered in the Milky Way, the three discovered in Andromeda Galaxy are M31WFS C1 M31WFS C2, and M31WFS C3. These new-found star clusters contain hundreds of thousands of stars, a number of stars that can be found in globular clusters. The clusters also share characteristics with globular clusters, e. g. the stellar populations. What distinguishes them from the clusters is that they are much larger – several hundred light-years across –. The distances between the stars are, therefore, much greater within the newly discovered extended clusters, parametrically, these clusters lie somewhere between a globular cluster and a dwarf spheroidal galaxy. How these clusters are formed is not yet known, but their formation might well be related to that of globular clusters, why M31 has such clusters, while the Milky Way has not, is not yet known
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Nebula
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A nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, nebula was a name for any diffuse astronomical object, the Andromeda Galaxy, for instance, was once referred to as the Andromeda Nebula before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher, Edwin Hubble and others. Most nebulae are of vast size, even millions of years in diameter. The Orion Nebula, the brightest nebula in the sky that occupies a region twice the diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers. Many nebulae are visible due to their fluorescence caused by the hot stars, while others are so diffuse they can only be detected with long exposures. Some nebulae are variably illuminated by T Tauri variable stars, Nebulae are often star-forming regions, such as in the Pillars of Creation in the Eagle Nebula. In these regions the formations of gas, dust, and other materials together to form denser regions, which attract further matter. The remaining material is believed to form planets and other planetary system objects. Around 150 AD, Claudius Ptolemaeus recorded, in books VII–VIII of his Almagest and he also noted a region of nebulosity between the constellations Ursa Major and Leo that was not associated with any star. The first true nebula, as distinct from a cluster, was mentioned by the Persian astronomer Abd al-Rahman al-Sufi. He noted a little cloud where the Andromeda Galaxy is located and he also cataloged the Omicron Velorum star cluster as a nebulous star and other nebulous objects, such as Brocchis Cluster. The supernova that created the Crab Nebula, the SN1054, was observed by Arabic, in 1610, Nicolas-Claude Fabri de Peiresc discovered the Orion Nebula using a telescope. This nebula was observed by Johann Baptist Cysat in 1618. However, the first detailed study of the Orion Nebula was not performed until 1659 by Christiaan Huygens, in 1715, Edmund Halley published a list of six nebulae. This number steadily increased during the century, with Jean-Philippe de Cheseaux compiling a list of 20 in 1746, from 1751 to 1753, Nicolas Louis de Lacaille cataloged 42 nebulae from the Cape of Good Hope, most of which were previously unknown. Charles Messier then compiled a catalog of 103 nebulae by 1781, his interest was detecting comets, the number of nebulae was then greatly expanded by the efforts of William Herschel and his sister Caroline Herschel. Their Catalogue of One Thousand New Nebulae and Clusters of Stars was published in 1786, a second catalog of a thousand was published in 1789 and the third and final catalog of 510 appeared in 1802. During much of their work, William Herschel believed that these nebulae were merely unresolved clusters of stars, in 1790, however, he discovered a star surrounded by nebulosity and concluded that this was a true nebulosity, rather than a more distant cluster
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Astrophotography
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Astrophotography is a specialized type of photography for recording photos of astronomical objects and large areas of the night sky. The first photograph of an object was taken in 1840. This is done by long time exposure since both film and digital cameras can accumulate and sum light photons over long periods of time. Astrophotography is a subdiscipline in amateur astronomy usually seeking aesthetically pleasing images rather than scientific data. Amateurs use a range of special equipment and techniques. With a few exceptions, astronomical photography employs long exposures since both film and digital imaging devices can accumulate and light photons over long periods of time, the amount of light hitting the film or detector is also increased by increasing the diameter of the primary optics being used. Since the Earth is constantly rotating, telescopes and equipment are rotated in the direction to follow the apparent motion of the stars overhead. This is accomplished by using either equatorial or computer-controlled altazimuth telescope mounts to keep celestial objects centered while the earth rotates, all telescope mount systems suffer from induced tracking error due to imperfect motor drives and mechanical sag of the telescope. Tracking errors are corrected by keeping a selected aiming point, usually a bright guide star, sometimes the object to be imaged is moving, so the telescope has to be kept constantly centered on that object. Guiding was formerly done manually throughout the exposure with an observer standing at the telescope making corrections to keep a cross hair on the guide star, since the advent of computer-controlled systems this is accomplished by an automated systems in professional and even amateur equipment. These all require specialized equipment such as telescopes designed for imaging, for wide field of view. Astronomical CCD cameras may use cryogenic cooling to reduce thermal noise, specialized filters are also used to record images in specific wavelengths. The development of astrophotography as a tool was pioneered in the mid-19th century for the most part by experimenters and amateur astronomers. Because of the long exposures needed to capture relatively faint astronomical objects. Early photographic processes also had limitations, the daguerreotype process was far too slow to record anything but the brightest objects, and the wet plate collodion process limited exposures to the time the plate could stay wet. The first-known attempt at astronomical photography was by Louis Jacques Mandé Daguerre, inventor of the process which bears his name. Tracking errors in guiding the telescope during the long exposure meant the photograph came out as an indistinct fuzzy spot, the Sun may have been first photographed in an 1845 daguerreotype by the French physicists Léon Foucault and Hippolyte Fizeau. No photographic alteration was caused by the light of the corona condensed by a lens for two minutes, during totality, on a sheet of paper prepared with bromide of silver, the Suns solar corona was first successfully imaged during the Solar eclipse of July 28,1851
31.
Charge-coupled device
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A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by shifting the signals between stages within the one at a time. CCDs move charge between capacitive bins in the device, with the shift allowing for the transfer of charge between bins, in recent years CCD has become a major technology for digital imaging. In a CCD image sensor, pixels are represented by p-doped metal-oxide-semiconductors capacitors, the charge-coupled device was invented in 1969 at AT&T Bell Labs by Willard Boyle and George E. Smith. The lab was working on bubble memory when Boyle and Smith conceived of the design of what they termed, in their notebook. The device could be used as a shift register, the essence of the design was the ability to transfer charge along the surface of a semiconductor from one storage capacitor to the next. The concept was similar in principle to the device, which was developed at Philips Research Labs during the late 1960s. The first patent on the application of CCDs to imaging was assigned to Michael Tompsett, the initial paper describing the concept listed possible uses as a memory, a delay line, and an imaging device. The first experimental device demonstrating the principle was a row of closely spaced metal squares on a silicon surface electrically accessed by wire bonds. The first working CCD made with integrated circuit technology was a simple 8-bit shift register and this device had input and output circuits and was used to demonstrate its use as a shift register and as a crude eight pixel linear imaging device. Development of the device progressed at a rapid rate, by 1971, Bell researchers led by Michael Tompsett were able to capture images with simple linear devices. Several companies, including Fairchild Semiconductor, RCA and Texas Instruments, picked up on the invention, fairchilds effort, led by ex-Bell researcher Gil Amelio, was the first with commercial devices, and by 1974 had a linear 500-element device and a 2-D100 x 100 pixel device. Steven Sasson, an engineer working for Kodak, invented the first digital still camera using a Fairchild 100 x 100 CCD in 1975. The first KH-11 KENNAN reconnaissance satellite equipped with charge-coupled device array technology for imaging was launched in December 1976, under the leadership of Kazuo Iwama, Sony also started a large development effort on CCDs involving a significant investment. Eventually, Sony managed to mass-produce CCDs for their camcorders, before this happened, Iwama died in August 1982, subsequently, a CCD chip was placed on his tombstone to acknowledge his contribution. He was also awarded the 2012 IEEE Edison Medal For pioneering contributions to imaging devices including CCD Imagers, cameras, in a CCD for capturing images, there is a photoactive region, and a transmission region made out of a shift register. An image is projected through a lens onto the capacitor array, once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbor. The last capacitor in the array dumps its charge into a charge amplifier, by repeating this process, the controlling circuit converts the entire contents of the array in the semiconductor to a sequence of voltages
32.
Electromagnetic spectrum
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The electromagnetic spectrum is the collective term for all known frequencies and their linked wavelengths of the known photons. The electromagnetic spectrum of an object has a different meaning, and is instead the characteristic distribution of radiation emitted or absorbed by that particular object. Visible light lies toward the end, with wavelengths from 400 to 700 nanometres. The limit for long wavelengths is the size of the universe itself, until the middle of the 20th century it was believed by most physicists that this spectrum was infinite and continuous. Nearly all types of radiation can be used for spectroscopy, to study. Other technological uses are described under electromagnetic radiation, for most of history, visible light was the only known part of the electromagnetic spectrum. The ancient Greeks recognized that light traveled in straight lines and studied some of its properties, the study of light continued, and during the 16th and 17th centuries conflicting theories regarded light as either a wave or a particle. The first discovery of electromagnetic radiation other than visible light came in 1800 and he was studying the temperature of different colors by moving a thermometer through light split by a prism. He noticed that the highest temperature was beyond red and he theorized that this temperature change was due to calorific rays that were a type of light ray that could not be seen. The next year, Johann Ritter, working at the end of the spectrum. These behaved similarly to visible light rays, but were beyond them in the spectrum. They were later renamed ultraviolet radiation, during the 1860s James Maxwell developed four partial differential equations for the electromagnetic field. Two of these equations predicted the possibility of, and behavior of, analyzing the speed of these theoretical waves, Maxwell realized that they must travel at a speed that was about the known speed of light. This startling coincidence in value led Maxwell to make the inference that light itself is a type of electromagnetic wave, maxwells equations predicted an infinite number of frequencies of electromagnetic waves, all traveling at the speed of light. This was the first indication of the existence of the electromagnetic spectrum. Maxwells predicted waves included waves at very low compared to infrared. Hertz found the waves and was able to infer that they traveled at the speed of light, Hertz also demonstrated that the new radiation could be both reflected and refracted by various dielectric media, in the same manner as light. For example, Hertz was able to focus the waves using a lens made of tree resin, in a later experiment, Hertz similarly produced and measured the properties of microwaves
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Visible spectrum
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The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called light or simply light. A typical human eye will respond to wavelengths from about 390 to 700 nm, in terms of frequency, this corresponds to a band in the vicinity of 430–770 THz. The spectrum does not, however, contain all the colors that the human eyes, unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths. Colors containing only one wavelength are called pure colors or spectral colors. Visible wavelengths pass through the window, the region of the electromagnetic spectrum that allows wavelengths to pass largely unattenuated through the Earths atmosphere. An example of this phenomenon is that clean air scatters blue light more than red wavelengths, the optical window is also referred to as the visible window because it overlaps the human visible response spectrum. The near infrared window lies just out of the vision, as well as the Medium Wavelength IR window. In the 13th century, Roger Bacon theorized that rainbows were produced by a process to the passage of light through glass or crystal. In the 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light and he was the first to use the word spectrum in this sense in print in 1671 in describing his experiments in optics. The result is red light is bent less sharply than violet as it passes through the prism. Newton divided the spectrum into seven named colors, red, orange, yellow, green, blue, indigo, the human eye is relatively insensitive to indigos frequencies, and some people who have otherwise-good vision cannot distinguish indigo from blue and violet. For this reason, some commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right. However, the evidence indicates that what Newton meant by indigo, comparing Newtons observation of prismatic colors to a color image of the visible light spectrum shows that indigo corresponds to what is today called blue, whereas blue corresponds to cyan. In the 18th century, Goethe wrote about optical spectra in his Theory of Colours, Goethe used the word spectrum to designate a ghostly optical afterimage, as did Schopenhauer in On Vision and Colors. Goethe argued that the spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish-yellow, the spectrum appears only when these edges are close enough to overlap. Young was the first to measure the wavelengths of different colors of light, the connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century
34.
Radio astronomy
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Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an object was in 1932. Subsequent observations have identified a number of different sources of radio emission and these include stars and galaxies, as well as entirely new classes of objects, such as radio galaxies, quasars, pulsars, and masers. The discovery of the microwave background radiation, regarded as evidence for the Big Bang theory, was made through radio astronomy. Before Jansky observed the Milky Way in the 1930s, physicists speculated that radio waves could be observed from astronomical sources, in the 1860s, James Clerk Maxwells equations had shown that electromagnetic radiation is associated with electricity and magnetism, and could exist at any wavelength. These attempts were unable to detect any emission due to limitations of the instruments. The discovery of the radio reflecting ionosphere in 1902, led physicists to conclude that the layer would bounce any astronomical radio transmission back into space, Karl Jansky made the discovery of the first astronomical radio source serendipitously in the early 1930s. As an engineer with Bell Telephone Laboratories, he was investigating static that interfered with short wave transatlantic voice transmissions, using a large directional antenna, Jansky noticed that his analog pen-and-paper recording system kept recording a repeating signal of unknown origin. Since the signal peaked about every 24 hours, Jansky originally suspected the source of the interference was the Sun crossing the view of his directional antenna. Continued analysis showed that the source was not following the 24-hour daily cycle of the Sun exactly and he concluded that since the Sun were not large emitters of radio noise, the strange radio interference may be generated by interstellar gas and dust in the galaxy. Jansky announced his discovery in 1933 and he wanted to investigate the radio waves from the Milky Way in further detail, but Bell Labs reassigned him to another project, so he did no further work in the field of astronomy. His pioneering efforts in the field of astronomy have been recognized by the naming of the fundamental unit of flux density. Grote Reber was inspired by Janskys work, and built a radio telescope 9m in diameter in his backyard in 1937. He began by repeating Janskys observations, and then conducted the first sky survey in the radio frequencies, on February 27,1942, James Stanley Hey, a British Army research officer, made the first detection of radio waves emitted by the Sun. Later that year George Clark Southworth, at Bell Labs like Jansky, both researchers were bound by wartime security surrounding radar, so Reber, who was not, published his 1944 findings first. Several other people independently discovered solar radiowaves, including E. Schott in Denmark, at Cambridge University, where ionospheric research had taken place during World War II, J. A. This early research soon branched out into the observation of celestial radio sources. Martin Ryle and Antony Hewish at the Cavendish Astrophysics Group developed the technique of Earth-rotation aperture synthesis, the radio astronomy group in Cambridge went on to found the Mullard Radio Astronomy Observatory near Cambridge in the 1950s
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Grote Reber
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Grote Reber was a pioneer of radio astronomy, which combined his interests in amateur radio and amateur astronomy. He was instrumental in investigating and extending Karl Janskys pioneering work and his 1937 radio antenna was the second ever to be used for astronomical purposes and the first parabolic reflecting antenna to be used as a radio telescope. For nearly a decade he was the only radio astronomer. Reber was born and raised in Wheaton, Illinois, a suburb of Chicago and he was an amateur radio operator, and worked for various radio manufacturers in Chicago from 1933 to 1947. When he learned of Karl Janskys work in 1933, he decided this was the field he wanted to work in, and applied to Bell Labs, however this was during the height of the Great Depression and there were no jobs available. In the summer of 1937, Reber decided to build his own radio telescope in his yard in Wheaton. Rebers radio telescope was more advanced than Janskys, and consisted of a parabolic sheet metal dish 9 meters in diameter. The entire assembly was mounted on a stand, allowing it to be pointed in various directions. The telescope was completed in September 1937, Rebers first receiver operated at 3300 MHz and failed to detect signals from outer space, as did his second, operating at 900 MHz. Finally, his attempt, at 160 MHz, was successful in 1938. In 1940, he achieved his first professional publication, in the Astrophysical Journal and he turned his attention to making a radiofrequency sky map, which he completed in 1941 and extended in 1943. He published a body of work during this era, and was the initiator of the explosion of radio astronomy in the immediate post-Second World War era. His data, published as contour maps showing the brightness of the sky in radio wavelengths, revealed the existence of sources such as Cygnus A. During this time he uncovered a mystery that was not explained until the 1950s, the standard theory of radio emissions from space was that they were due to black-body radiation, light that is given off by all hot bodies. Using this theory one would expect that there would be considerably more high-energy light than low-energy, due to the presence of stars, however Reber demonstrated that the reverse was true, and that there was a considerable amount of low-energy radio signal. It was not until the 1950s that synchrotron radiation was offered as an explanation for these measurements, Reber sold his telescope to the National Bureau of Standards, and it was erected on a turntable at their field station in Sterling, Virginia. Eventually the telescope made its way to NRAO in Green Bank, West Virginia, Reber also helped with a reconstruction of Janskys original telescope. Starting in 1951, he received support from the Research Corporation in New York
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Radio telescope
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A radio telescope is a specialized antenna and radio receiver used to receive radio waves from astronomical radio sources in the sky in radio astronomy. Radio telescopes are typically large parabolic antennas similar to those employed in tracking and communicating with satellites and they may be used singly, or linked together electronically in an array. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night, Radio waves from space were first detected by engineer Karl Guthe Jansky in 1932 at Bell Telephone Laboratories in Holmdel, New Jersey using an antenna built to study noise in radio receivers. The first purpose-built radio telescope was a 9-meter parabolic dish constructed by radio amateur Grote Reber in his yard in Wheaton. The sky survey he did with it is considered the beginning of the field of radio astronomy. The first radio antenna used to identify an astronomical radio source was one built by Karl Guthe Jansky, Jansky was assigned the job of identifying sources of static that might interfere with radio telephone service. Janskys antenna was an array of dipoles and reflectors designed to receive short wave radio signals at a frequency of 20.5 MHz and it was mounted on a turntable that allowed it to rotate in any direction, earning it the name Janskys merry-go-round. It had a diameter of approximately 100 ft and stood 20 ft tall, by rotating the antenna, the direction of the received interfering radio source could be pinpointed. A small shed to the side of the antenna housed an analog recording system. Jansky finally determined that the faint hiss repeated on a cycle of 23 hours and 56 minutes and this period is the length of an astronomical sidereal day, the time it takes any fixed object located on the celestial sphere to come back to the same location in the sky. An amateur radio operator, Grote Reber, was one of the pioneers of what became known as radio astronomy and he built the first parabolic dish radio telescope, a 9 metres in diameter) in his back yard in Wheaton, Illinois in 1937. The range of frequencies in the spectrum that makes up the radio spectrum is very large. This means that the types of antennas that are used as radio telescopes vary widely in design, size, at wavelengths of 30 meters to 3 meters, they are generally either directional antenna arrays similar to TV antennas or large stationary reflectors with moveable focal points. Since the wavelengths being observed with these types of antennas are so long, at shorter wavelengths parabolic dish antennas predominate. The angular resolution of an antenna is determined by the ratio of the diameter of the dish to the wavelength of the radio waves being observed. This dictates the size a radio telescope needs for a useful resolution. Radio telescopes that operate at wavelengths of 3 meters to 30 cm are usually well over 100 meters in diameter, telescopes working at wavelengths shorter than 30 cm range in size from 3 to 90 meters in diameter. The Wilkinson Microwave Anisotropy Probe mapped the Cosmic microwave background radiation in 5 different frequency bands, centered on 23 GHz,33 GHz,41 GHz,61 GHz, the worlds largest filled-aperture radio telescope is the Five hundred meter Aperture Spherical Telescope completed in 2016 by China
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Karl Guthe Jansky
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Karl Guthe Jansky was an American physicist and radio engineer who in August 1931 first discovered radio waves emanating from the Milky Way. He is considered one of the figures of radio astronomy. Karl Guthe Jansky was born in what was then the Territory of Oklahoma where his father, Cyril M. Jansky, born in Wisconsin of Czech immigrants, had started teaching at the age of sixteen. He was a teacher throughout his life, retiring as Professor of Electrical Engineering at the University of Wisconsin. He was an engineer with a strong interest in physics, a trait passed on to his sons, Karl Jansky was named after Dr. Karl Eugen Guthe, a Professor of Physics at the University of Michigan who had been an important mentor to Cyril M. Jansky. Karl Janskys mother, born Nellie Moreau, was of French, karls brother Cyril Jansky Jr. who was ten years older, helped build some of the earliest radio transmitters in the country, including 9XM in Wisconsin and 9XI in Minnesota. Karl Jansky attended college at the University of Wisconsin–Madison where he received his BS in physics in 1927, in 1928 he joined the Bell Telephone Laboratories site in Holmdel, New Jersey. Bell Labs wanted to investigate atmospheric and ionospheric properties using short waves for use in transatlantic radio telephone service, as a radio engineer, Jansky was assigned the job of investigating sources of static that might interfere with radio voice transmissions. At Bell Telephone Laboratories Jansky built an antenna designed to receive radio waves at a frequency of 20.5 MHz and it was mounted on a turntable that allowed it to be rotated in any direction, earning it the name Janskys merry-go-round. It had a diameter of approximately 100 ft. and stood 20 ft. tall, by rotating the antenna on a set of four Ford Model-T tires, the direction of a received signal could be pinpointed. A small shed to the side of the antenna housed an analog recording system. He spent over a year investigating the source of the type of static. The location of maximum intensity rose and fell once a day, after a few months of following the signal, however, the brightest point moved away from the position of the Sun. Jansky also determined that the signal repeated on a cycle of 23 hours and 56 minutes and his discovery was widely publicized, appearing in the New York Times of May 5,1933. He published his classic paper Electrical disturbances apparently of extraterrestrial origin in Proc and this paper was re-printed in Proc. IEEE in 1984 and again in 1998, for the first centennial of radio, Jansky wanted to follow up on this discovery and investigate the radio waves from the Milky Way in further detail. He submitted a proposal to Bell Labs to build a 30 meter diameter dish antenna with greater sensitivity that would allow more careful measurements of the structure and strength of the radio emission. Bell Labs, however, rejected his request for funding on the grounds that the emission would not significantly affect their planned transatlantic communications system
38.
Infrared cut-off filter
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Infrared cut-off filters, sometimes called IR filters or heat-absorbing filters, are designed to reflect or block mid-infrared wavelengths while passing visible light. They are often used in devices with bright incandescent light bulbs to prevent unwanted heating, there are also filters which are used in solid state video cameras to block IR due to the high sensitivity of many camera sensors to near-infrared light. These filters typically have a hue to them as they also sometimes block some of the light from the longer red wavelengths. Thus a blue filter makes the picture look blue, a black filter marginally allows more light in the blue wavelength to pass resulting in a slight shift of the color temperature of the photo to a cooler color. Because of this, the term IR filters is used to refer to filters that pass infrared light while completely blocking other wavelengths. However, in applications the term IR filter still can be used as a synonym of infrared cut-off filter. Unlike the eye, sensors based on silicon have sensitivities extending into the near-infrared, such sensors may extend to 1000 nm. Digital cameras are equipped with IR-blocking filters to prevent unnatural-looking images. IR-transmitting filters, or removal of factory IR-blocking filters, are used in infrared photography to pass infrared light and block visible. Such filters appear black to the eye, but are transparent when viewed with an IR sensitive device, such filters can be used both over color camera lenses, and to filter visible light from IR illumination sources. Such filter stock is most easily made available most simply by having any commercial color negative film developed after being exposed to light. The leaders of 35mm film are ideal for this, without wasting an entire roll of film, in the same way, visually opaque black color-positive film emulsions mounted in cardboard, as for routine slide projection, provide inexpensive cardboard-mounted infrared filters. Film sizes larger than 35 mm may be handled in the way for larger filter production. For astrophotography, many photogenic targets are bright in the far red, removal of factory filters increases sensitivity to such targets, and may also increase sharpness, as such filters may also include anti-aliasing filters. UV filter Cold mirror and Hot mirror Interference filter
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One-Mile Telescope
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The One-Mile Telescope at the Mullard Radio Astronomy Observatory is an array of radio telescopes designed to perform aperture synthesis interferometry. The One Mile Telescope was completed by the Radio Astronomy Group of Cambridge University in 1964, the telescope was used to produce the 5C catalogue of radio sources. Observations with larger incremental spacings were used to observe individual radio sources with unprecedented sensitivity, angular resolution and these surveys required intensive use of inverse Fourier Transforms, and were made possible by development of a new generation of computers such as the Titan. In 1971, Sir Martin Ryle described why, in the late 1950s, radio astronomers at MRAO decided on the construction of the new One Mile telescope, Our object was twofold. First we wanted to extend the range of our observations far back in time to the earliest days of the Universe, One of the One Mile Telescope dishes was temporarily used to improve the resolution of MERLIN from 1987 until Autumn 1990. The One-Mile Telescope, was the first to use Earth-rotation aperture synthesis, the telescope was made up of three 120 ton dishes, each of which is 18 m in diameter. Two of the dishes are fixed, while the third can be moved along an 800 m long rail track, at speeds of up to 6.4 km/h. There were 60 different stations along the track, which is straight to within 0.9 cm, the observing frequencies were usually 408 MHz and 1.4 GHz. Over a 20-year career, the telescope was used to map individual objects, though still occasionally used, it is now essentially retired. Two antennae of the One-Mile Telescope on Google Maps Coordinates,52. 1636°N0. 0371°E /52.1636,0.0371
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Paranal Observatory
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By total light-collecting area, it is the largest optical-infrared observatory in the Southern hemisphere, worldwide, it is second to the Mauna Kea Observatory on Hawaii. The Very Large Telescope, the largest telescope on Paranal, is composed of four separate 8.2 m telescopes, in addition, the four main telescopes can combine their light to make a fifth instrument, the Very Large Telescope Interferometer. Four auxiliary telescopes of 1.8 m each are part of the VLTI to make it available when the main telescopes are being used for other projects. The site also houses the 2.6 m VLT Survey Telescope and 4.0 m VISTA survey telescope with wider fields of view for surveying large areas of sky uniformly. From an aerial view of the Paranal Oberservatory, the four units of the VLT with their four small. The Survey Telescope, VST, is adjacent to the VLT. The Very Large Telescope consists of four 8. 2-metre telescopes operating in the visible and these telescopes, along with four smaller auxiliary telescopes, are also combined to operate as an optical interferometer on certain nights of the year. All of the 8. 2-metre telescopes have adaptive optics and a suite of instruments. VISTA is the Visible & Infrared Survey Telescope for Astronomy, a 4. 0-metre telescope with a field of view. It was built close to ESOs VLT by a consortium of 18 universities from the United Kingdom, VISTA was handed over to the European Southern Observatory in December 2009. The VLT Survey Telescope or VST is a 2. 6-metre telescope with a wide field imager intended to aid the four Very Large Telescope in their scientific aims, the Next-Generation Transit Survey is an exoplanet-survey facility located a few kilometers from the main peak. It consists of an array of twelve 0. 2-meter robotic telescopes with a large field of view of 96 square degrees or several hundred times the area of the full moon. The survey aims to discover numerous super-Earths and Neptune-sized planets around nearby stars, NGTS is managed by a partnership of seven academic institutions from Chile, Germany, Switzerland and the United Kingdom and its design is based on the SuperWASP project. Science operations began in early 2015, as well as the telescopes, control buildings and maintenance facilities, Paranal has a Residencia which provides accommodation for staff and visitors. This is located 200 m lower and 3 km from the telescopes and it is built half into the mountain with the concrete coloured to blend into the landscape. It has gym facilities, a pool, a restaurant. The construction was decorated by the Chilean architect Paula Gutiérrez Erlandsen, the VLT hotel, the Residencia, served as a backdrop for part of the 2008 James Bond film Quantum of Solace. The observatorys facilities were used to stage the Pacific Alliances fourth summit in June 2012, on 14 March 2013, Frederik, Crown Prince of Denmark, accompanied by his wife, Princess Mary, visited ESO’s Paranal Observatory, as part of an official visit to Chile
41.
Camera
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Thumb|A2016 Nikon D810 A camera is an optical instrument for recording or capturing images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies, the camera is a remote sensing device as it senses subjects without physical contact. The word camera comes from camera obscura, which means dark chamber and is the Latin name of the device for projecting an image of external reality onto a flat surface. The modern photographic camera evolved from the camera obscura, the functioning of the camera is very similar to the functioning of the human eye. A camera may work with the light of the spectrum or with other portions of the electromagnetic spectrum. A still camera is a device which creates a single image of an object or scene. All cameras use the basic design, light enters an enclosed box through a converging lens/convex lens. A shutter mechanism controls the length of time that light can enter the camera, a display, often a liquid crystal display, permits the user to view scene to be recorded and settings such as ISO speed, exposure, and shutter speed. A movie camera or a video camera operates similarly to a camera, except it records a series of static images in rapid succession. When the images are combined and displayed in order, the illusion of motion is achieved, the forerunner to the photographic camera was the camera obscura. The oldest known record of this principle is a description by Han Chinese philosopher Mozi, Mozi correctly asserted that the camera obscura image is inverted because light travels in straight lines from its source. In the 11th century Arab physicist Ibn al-Haytham s wrote very influential essays about experiments with light through an opening in a darkened room. The use of a lens in the opening of a wall or closed window shutter of a room to project images used as a drawing aid has been traced back to circa 1550. Since the late 17th century portable camera obscura devices in tents, before the development of the photographic camera, it had been known for hundreds of years that some substances, such as silver salts, darkened when exposed to sunlight. The first person to use this chemistry to create images was Thomas Wedgwood, to create images, Wedgwood placed items, such as leaves and insect wings, on ceramic pots coated with silver nitrate, and exposed the set-up to light. These images werent permanent, however, as Wedgwood didnt employ a fixing mechanism and he ultimately failed at his goal of using the process to create fixed images created by a camera obscura. The first permanent photograph of an image was made in 1826 by Joseph Nicéphore Niépce using a sliding wooden box camera made by Charles. Niépce had been experimenting with ways to fix the images of a camera obscura since 1816, the photograph Niépce succeeded in creating shows the view from his window
42.
Amateur telescope making
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Amateur telescope making is the activity of building telescopes as a hobby, as opposed to being a paid professional. Amateur telescope makers are usually a sub-group in the field of amateur astronomy, ever since Galileo took a Dutch invention and adapted it to astronomical use, astronomical telescope making has been an evolving discipline. Before the advent of modern mass-produced telescopes the price of even a modest instrument was often beyond the means of an amateur astronomer. Building your own was the only method to obtain a suitable telescope for observing. There were many published works that helped spark an interest in building such as Irish telescope maker Rev. W. F. A. Ellisons 1920 book The Amateurs Telescope. There was so much public interest Ingalls began a column for Scientific American on the subject. These had a readership of enthusiast constructing their own instruments. Between 1933 and 1990, Sky and Telescope magazine ran a column called Gleanings for ATMs edited by Earle Brown. The ready supply of surplus optical components after World War 2 and later Sputnik, porter as “The Poor Mans Telescope”. The Newtonian has the advantage of being a design that allows for maximum size for the minimum expense. Typically a Newtonian telescope of 6” or 8 aperture is a starter project. Since the Newtonian reflector is the most common telescope built by amateur telescope makers, the mirror has to be carefully ground, polished and figured to an extremely accurate shape, usually a paraboloid. Telescopes with high focal ratios may use spherical mirrors since the difference in the two shapes is insignificant at those ratios. The tools used to achieve this shape are surprisingly simple, consisting of a similarly sized glass tool, a series of finer abrasives, through a whole series of random strokes the mirror naturally tends to become spherical in shape. At that point, a variation in polishing strokes is used to create. In order to grind telescope optics into a shape, a highly versatile material must be used such as glass. After the melting point is reached, the glass fuses together, proper annealing procedures ensure that internal stresses are relieved within the glass, which reduces risk of failure for the newly cast blank. The equipment most amateurs use to test the shape of the mirrors, at its most basic it consists of a light bulb, a piece of tinfoil with a pinhole in it, and a razorblade
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Star chart
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A star chart is another name for a chore chart. A star chart or star map is a map of the night sky, astronomers divide these into grids to use them more easily. They are used to identify and locate objects such as stars, constellations. They have been used for navigation since time immemorial. Note that a star chart differs from a catalog, which is a listing or tabulation of astronomical objects for a particular purpose. Tools utilizing a star chart include the astrolabe and the planisphere, the oldest known star chart may be a carved ivory Mammoth tusk that was discovered in Germany in 1979. This artifact is 32,500 years old and has a carving that resembles the constellation Orion, a drawing on the wall of the Lascaux caves in France has a graphical representation of the Pleiades open cluster of stars. This is dated from 33,000 to 10,000 years ago, another star chart panel, created more than 21,000 years ago, was found in the La Tête du Lion grotto. The bovine in this panel may represent the constellation Taurus, with a representing the Pleiades just above it. The oldest accurately dated star chart appeared in ancient Egyptian astronomy in 1534 BC, the earliest known star catalogues were compiled by the ancient Babylonian astronomers of Mesopotamia in the late 2nd millennium BC, during the Kassite Period. The oldest Chinese astronomy records date to before the Warring States period, the oldest Chinese graphical representation of the sky is a lacquer box dated to 430 BC, although this depiction does not show individual stars. The Farnese Atlas is a 2nd-century copy of a Hellenistic era statue depicting the Titan Atlas holding the sphere on his shoulder. It is the oldest surviving depiction of the ancient Greek constellations, because of precession, the positions of the constellations slowly change over time. By comparing the positions of the 41 constellations against the grid circles, based upon this information, the constellations were catalogued at 125 ±55 BC. This evidence indicates that the catalogue of the Greek astronomer Hipparchus was used. A Roman era example of a representation of the night sky is the Egyptian Dendera zodiac. This is a bas relief sculpting on a ceiling at the Dendera Temple complex and it is a planisphere depicting the zodiac in graphical representations. However, individual stars are not plotted, the oldest surviving manuscript star chart was discovered in the Mogao Caves along the Silk Road – the Dunhuang Star Chart
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Planisphere
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In astronomy, planisphere is a star chart analog computing instrument in the form of two adjustable disks that rotate on a common pivot. It can be adjusted to display the stars for any time. It is an instrument to assist in learning how to recognize stars, the astrolabe, an instrument that has its origins in Hellenistic astronomy, is a predecessor of the modern planisphere. The term planisphere contrasts with armillary sphere, where the sphere is represented by a three-dimensional framework of rings. The chart and overlay are mounted so that they are free to rotate about a pivot point at their centers. The star chart contains the brightest stars, constellations and deep-sky objects visible from a latitude on Earth. The night sky that one sees from the Earth depends on whether the observer is in the northern or southern hemispheres, a planisphere window is designed for a particular latitude and will be accurate enough for a certain band either side of that. Planisphere makers will usually offer them in a number of versions for different latitudes, planispheres only show the stars visible from the observers latitude, stars below the horizon are not included. A complete twenty-four-hour time cycle is marked on the rim of the overlay, a full twelve months of calendar dates are marked on the rim of the starchart. The window is marked to show the direction of the eastern and western horizons, the disk and overlay are adjusted so that the observers local time of day on the overlay corresponds to that days date on the star chart disc. The portion of the star visible in the window then represents the distribution of stars in the sky at that moment for the planispheres designed location. Users hold the planisphere above their head with the eastern and western horizons correctly aligned to match the chart to actual star positions, the word planisphere was originally used in the second century by Ptolemy to describe the representation of a spherical Earth by a map drawn in the plane. This usage continued into the Renaissance, for example Gerardus Mercator described his 1569 world map as a planisphere, in this article the word describes the representation of the star-filled celestial sphere on the plane. The first star chart to have the name planisphere was made in 1624 by Jacob Bartsch, Bartsch was the son-in-law of Johannes Kepler, discoverer of Keplers laws of planetary motion. Since the planisphere shows the sphere in a printed flat. Planispheres, like all charts, are using a certain projection method. For planispheres there are two methods in use, leaving the choice with the designer. One such method is the azimuthal equidistant projection
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. Bibcode:2011ApJ...727..117M. doi:10.1088/0004-637X/727/2/117. ISSN 0004-637X.
