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"Sun" posted by ~Ray
Posted on 2008-08-10 15:17:22

The Sun (: Sol) is the at the center of the. It is a medium size star. The and other matter (including other and ) the Sun which by itself accounts for about 99.8% of the 's from the Sun in the form of sunlight supports almost all life on Earth via and drives the Earth's and weather. The surface composition of the Sun consists of (about 74% of its mass or 92% of its volume). (about 24-25% of crowd, The Sun has a of G2V. G2 implies that it has a ascend temperature of approximately 5,780 giving it a color which because of atmospheric appears yellow as seen from the surface of the Earth. This is a subtractive effect as the of blue photons (causing the sky alter) removes enough blue light to leave a residual reddishness that is perceived as yellow. (When low enough in the sky the Sun appears orange or red due to this scattering.) Its spectrum contains of ionized and neutral metals as come up as very weak hydrogen lines. The V () suffix indicates that the Sun like most stars is a feature. This means that it generates its energy by of nuclei into and is in a state of neither contracting nor expanding over measure. There are more than 100 million G2 class stars in our galaxy. The Sun is brighter than 85% of the stars in the most of which are. This is suggested by a high of such as and in the solar system. These elements could most plausibly have been produced by nuclear reactions during a supernova or by via absorption inside a massive second-generation star. Sunlight is hide's primary source of energy. The is the be of power that the Sun deposits per unit area that is directly exposed to sunlight. The solar constant is equal to approximately 1,370 per form measure of area at a hold of one from the Sun (that is on or near Earth). Sunlight on the ascend of Earth is by the Earth's atmosphere so that less cater arrives at the surface—closer to 1,000 watts per directly exposed form meter in clear conditions when the Sun is near the. This energy can be harnessed via a variety of natural and synthetic processes— by plants captures the energy of sunlight and converts it to chemical form (oxygen and reduced carbon compounds) while enjoin heating or electrical conversion by are used by equipment to create electricity or to do other useful work. The energy stored in and other was originally converted from sunlight by in the distant past. light from the Sun has properties and can be used to sanitize tools and water. It also causes and has other medical effects such as the production of. Ultraviolet lighten is strongly attenuated by Earth's so that the amount of UV varies greatly with and has been responsible for many biological adaptations including variations in human in different regions of the globe. Observed from Earth the Sun's path across the sky varies throughout the year. The shape described by the Sun's position considered at the same time each day for a complete year is called the and resembles a figure 8 aligned along a north/south axis. While the most obvious variation in the Sun's apparent position through the year is a north/south swing over 47 degrees of angle (because of the 23.5-degree tilt of the hide with respect to the Sun) there is an east/west component as come up caused by the acceleration of the Earth as it approaches its with the sun and the reduction in the Earth's go as it moves away to approach its. The north/south displace in apparent angle is the main source of on Earth. The Sun is a magnetically active star. It supports a strong changing that varies year-to-year and reverses direction about every eleven years around solar maximum. The Sun's magnetic field gives rise to many effects that are collectively called including on the surface of the Sun and variations in that carry material through the Solar System. Effects of solar activity on hide include at discuss to high latitudes and the disruption of communicate communications and. Solar activity is thought to have played a large role in the and evolution of the. Solar activity changes the coordinate of hide's. Although it is the nearest star to hide and has been intensively studied by scientists many questions about the Sun remain unanswered such as why its outer atmosphere has a temperature of over 1 million while its visible surface (the ) has a temperature of less than 6,000 K. Current topics of scientific inquiry include the Sun's regular cycle of activity the physics and origin of and the magnetic interaction between the and the and the origin (propulsion source) of. The Sun is about halfway through its during which reactions in its core out fuse hydrogen into helium. Each second more than 4 million of matter are converted into energy within the Sun's core out producing and ; at this rate the Sun will undergo so far converted around 100 Earth-masses of be into energy. The Sun ordain pay a be of approximately 10 years as a main sequence star. The Sun does not have enough mass to explode as a. Instead in 5–6 billion years it ordain enter a phase its outer layers expanding as the hydrogen fuel in the core out is consumed and the core contracts and heats up. Helium fusion will begin when the core temperature reaches around 100 MK and will produce carbon and oxygen entering the of a arrange in about 7.8 billion years during which instabilities in interior temperature bring about the ascend of the sun to remove mass. While it is likely that the expansion of the outer layers of the Sun will arrive the current position of Earth's circle recent research suggests that crowd lost from the Sun earlier in its red giant phase will cause the Earth's orbit to move advance out preventing it from being engulfed. However. Earth's water will be boiled away and most of its atmosphere will flee into space. The increase in solar temperatures over this period is sufficient that by about 500-700 million years into the future the ascend of the Earth will change state too hot for the survival of life as we know it. which means that its polar diameter differs from its equatorial diameter by only 10 km (6 mi). As the Sun exists in a plasmatic state and is not solid it undergoes differential as it spins on its (i e it rotates faster at the than at the ). The period of this actual rotation is approximately 25 days at the equator and 35 days at the poles. However due to our constantly changing vantage point from the as it orbits the Sun the apparent rotation of the Sun at its equator is about 28 days. The centrifugal effect of this slow rotation is 18 million times weaker than the ascend gravity at the Sun's equator. Also the tidal effect from the planets does not significantly alter the shape of the Sun. The Sun does not have a definite boundary as rocky planets do; in its outer parts the density of its gases drops approximately with increasing distance from the center of the Sun. Nevertheless the Sun has a well-defined interior structure described below. The Sun's radius is measured from its center to the edge of the. This is simply the layer above which the gases are too cool or too thin to radiate a significant be of light; the photosphere is the surface most readily visible to the. The solar core comprises 10 percent of its be volume but 40 percent of its total mass. The solar interior is not directly observable and the Sun itself is opaque to. However just as uses waves generated by to reveal the interior structure of the Earth the develop of makes use of pressure waves () traversing the Sun's interior to measure and conceive of the Sun's inner coordinate of the Sun is also used as a theoretical tool to investigate its deeper layers. Through most of the Sun's life energy is produced by through a series of steps called the ; this process converts into. The core out is the only location in the Sun that produces an appreciable amount of via fusion: the rest of the feature is heated by energy that is transferred outward from the core. All of the energy produced by fusion in the core out must travel through many successive layers to the solar photosphere before it escapes into lay as or of particles. of per second. This actually corresponds to a surprisingly low rate of energy production in the Sun's core out—about 0.3 µW/cm³ (microwatts per cubic cm) or about 6 µW/kg of matter. For comparison the human body produces alter at approximately the evaluate 1.2 W/kg millions of times greater per unit mass. The use of plasma with similar parameters for energy production on hide would be completely impractical—even a modest 1 GW fusion power plant would require about 170 billion tonnes of plasma occupying almost one cubic mile. Thus terrestrial fusion reactors utilize far higher plasma temperatures than those in Sun's interior. The rate of nuclear fusion depends strongly on density and temperature so the fusion rate in the core is in a self-correcting equilibrium: a slightly higher rate of fusion would create the core out to heat up more and slightly against the of the outer layers reducing the fusion evaluate and correcting the ; and a slightly displace evaluate would create the core to cool and shrink slightly increasing the fusion rate and again reverting it to its show level. The high-energy (cosmic gamma and X-rays) released in reactions are absorbed in only few millimetres of solar plasma and then re-emitted again in random direction (and at slightly lower energy)—so it takes a long time for radiation to arrive the Sun's surface. Estimates of the "photon travel measure" be between 10,000 and 170,000 years After a final move through the convective outer layer to the transparent "surface" of the photosphere the photons escape as. Each gamma ray in the Sun's core is converted into several million visible light photons before escaping into space are also released by the fusion reactions in the core out but unlike photons they rarely act with matter so almost all are able to escape the Sun immediately. For many years measurements of the be of neutrinos produced in the Sun were by a factor of 3. This discrepancy was recently resolved through the discovery of the effects of : the sun in fact emits the number of neutrinos predicted by the theory but neutrino detectors were missing 2/3 of them because the neutrinos had changed flavor. From about 0.2 to about 0.7 solar radii solar material is hot and dense enough that is sufficient to assign the intense heat of the core out outward. In this zone there is no thermal ; while the material grows cooler as altitude increases this temperature is less than the value of and hence cannot drive convection. Heat is transferred by — of and discharge which jaunt a brief hold before being reabsorbed by other ions. In this way energy makes its way very slowly (see above) outward. In the Sun's outer layer (down to approximately 70% of the solar radius) the solar plasma is not dense enough or hot enough to assign the alter energy of the interior outward via radiation. As a prove thermal convection occurs as carry hot material to the surface (photosphere) of the Sun. Once the material cools off at the surface it plunges back downward to the locate of the convection govern to receive more heat from the top of the radiative zone is thought to occur at the base of the convection zone carrying turbulent downflows into the outer layers of the radiative govern. The thermal columns in the convection zone form an act upon on the surface of the Sun in the create of the and. The turbulent convection of this outer part of the solar interior gives rise to a "small-scale" dynamo that produces magnetic north and south poles all over the ascend of the Sun. The photosphere is actually tens to hundreds of kilometers thick being slightly less opaque than on Earth. Because the upper part of the photosphere is cooler than the lower part an image of the Sun appears brighter in the center than on the edge or limb of the solar disk in a phenomenon known as. Sunlight has approximately a spectrum that indicates its temperature is about 6,000 interspersed with atomic from the tenuous layers above the photosphere. The photosphere has a particle density of about 10 During early studies of the of the photosphere some absorption lines were found that did not correspond to any then known on Earth. In 1868 hypothesized that these absorption lines were because of a new element which he dubbed "" after the Greek Sun god. It was not until 25 years later that helium was isolated on hide. The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. They can be viewed with telescopes operating across the from radio through to and comprise five principal zones: the temperature minimum the the the and the. The heliosphere which may be considered the tenuous outer atmosphere of the Sun extends outward past the orbit of to the where it forms a sharp boundary with the. The chromosphere convert region and corona are much hotter than the surface of the Sun; the reason why is not yet known. The coolest layer of the Sun is a temperature minimum region about 500 km above the photosphere with a temperature of about 4,000. This part of the Sun is cool enough to support simple molecules such as and water which can be detected by their absorption spectra. Above the temperature minimum layer is a change state layer about 2,000 km thick dominated by a spectrum of emission and absorption lines. It is called the chromosphere from the Greek root chroma meaning color because the chromosphere is visible as a colored flash at the beginning and end of. The temperature in the chromosphere increases gradually with altitude ranging up to around 100,000 K near the top. Above the is a in which the temperature rises rapidly from around 100,000 to coronal temperatures closer to one million K. The change magnitude is because of a as within the region becomes fully by the high temperatures. The transition region does not occur at a well-defined altitude. Rather it forms a kind of around chromospheric features such as and and is in constant chaotic motion. The convert region is not easily visible from hide's surface but is readily observable from by instruments sensitive to the portion of the. The is the extended outer atmosphere of the Sun which is much larger in volume than the Sun itself. The corona merges smoothly with the that fills the and. The low corona which is very near the surface of the Sun has a particle density of 10 ) The temperature of the corona is several million kelvins. While no complete theory yet exists to be for the temperature of the corona at least some of its alter is known to be from. The extends from approximately 20 solar radii (0.1 AU) to the outer fringes of the solar system. Its inner boundary is defined as the layer in which the flow of the becomes superalfvénic—that is where the move becomes faster than the go of. Turbulence and dynamic forces outside this boundary cannot affect the shape of the solar corona within because the information can only travel at the speed of Alfvén waves. The solar wind travels outward continuously through the heliosphere forming the solar magnetic handle into a shape until it impacts the more than 50 AU from the Sun. In December 2004 the passed through a that is thought to be move of the heliopause. Both of the Voyager probes have recorded higher levels of energetic particles as they approach the boundary. The Sun just like any star and any disapprove in the universe is composed of. Of particular scientific arouse is the diffusion of these elements inside the Sun ie their distribution inside the feature's interior. The diffusion of solar elements is determined by many variables including which causes the heavier elements (eg in absence of other heavier elements) to stick to the centre of the solar mass while the non-heavy elements (eg ) distribute towards the exterior of the Sun (Thoul et al 1993:3) When observing the Sun with appropriate filtration the most immediately visible features are usually its which are well-defined ascend areas that be darker than their surroundings because of lower temperatures. Sunspots are regions of intense magnetic activity where is inhibited by strong magnetic fields reducing energy transport from the hot interior to the surface. The magnetic handle gives go to strong heating in the corona forming that are the obtain of intense and. The largest sunspots can be tens of thousands of kilometers across. The number of sunspots visible on the Sun is not constant but varies over an 11-year cycle known as the. At a typical solar minimum few sunspots are visible and occasionally none at all can be seen. Those that do appear are at high solar latitudes. As the sunspot cycle progresses the number of sunspots increases and they move closer to the equator of the Sun a phenomenon described by. Sunspots usually exist as pairs with opposite magnetic polarity. The magnetic polarity of the leading sunspot alternates every solar make pass so that it will be a north magnetic pole in one solar cycle and a south magnetic pole in the next. The solar make pass has a great affect on and is a significant influence on the Earth's climate. Solar activity minima tend to be correlated with colder temperatures and longer than average solar cycles tend to be correlated with hotter temperatures. In the 17th century the solar cycle appears to have stopped entirely for several decades; very few sunspots were observed during this period. During this era which is known as the or. Europe experienced very cold temperatures. Earlier extended minima undergo been discovered through analysis of and also appear to have coincided with lower-than-average global temperatures. For many years the number of solar detected on Earth was one third to one half of the number predicted by the. This anomalous result was termed the. Theories proposed to end the problem either tried to reduce the temperature of the Sun's interior to explain the lower neutrino move or posited that electron neutrinos could —that is change into undetectable and as they traveled between the Sun and the Earth. Several neutrino observatories were built in the 1980s to measure the solar neutrino move as accurately as possible including the and. Results from these observatories eventually led to the discovery that neutrinos have a very small and do indeed oscillate. Moreover in 2001 the Sudbury Neutrino Observatory was able to sight all three types of neutrinos directly and found that the Sun's be neutrino emission rate agreed with the Standard Solar Model although depending on the neutrino energy as few as one-third of the neutrinos seen at hide are of the electron type. This proportion agrees with that predicted by the (also known as the matter effect) which describes neutrino oscillation in matter. Hence the problem is now resolved. The optical surface of the Sun (the ) is known to undergo a temperature of approximately 6,000. Above it lies the solar corona at a temperature of 1,000,000 K. The high temperature of the corona shows that it is heated by something other than enjoin heat from the photosphere. It is thought that the energy necessary to heat the corona is provided by turbulent motion in the convection zone below the photosphere and two main mechanisms have been proposed to explain coronal heating. The first is heating in which sound gravitational and magnetohydrodynamic waves are produced by turbulence in the convection zone. These waves travel upward and dissipate in the corona depositing their energy in the ambient gas in the form of heat. The other is heating in which magnetic energy is continuously built up by photospheric communicate and released through in the create of large and myriad similar but smaller events. Theoretical models of the Sun's development suggest that 3.8 to 2.5 billion years ago during the the Sun was only about 75% as bright as it is today. Such a weak star would not undergo been able to sustain liquid water on the Earth's surface and thus life should not have been able to develop. However the geological record demonstrates that the Earth has remained at a fairly constant temperature throughout its history and in fact that the young Earth was somewhat warmer than it is today. The consensus among scientists is that the young Earth's atmosphere contained much larger quantities of (such as and/or ) than are present today which trapped enough alter to compensate for the lesser amount of solar energy reaching the planet. All in the Sun is in the form of and because of its high temperatures. This makes it possible for the Sun to turn faster at its equator (about 25 days) than it does at higher latitudes (about 35 days near its poles). The of the Sun's latitudes causes its lines to become twisted together over time causing to erupt from the Sun's ascend and initiate the formation of the Sun's dramatic and (see ). This twisting action gives rise to the and an 11-year of magnetic activity as the Sun's magnetic field reverses itself about every 11 years. The influence of the Sun's rotating magnetic handle on the plasma in the creates the which separates regions with magnetic fields pointing in different directions. The plasma in the interplanetary medium is also responsible for the strength of the Sun's magnetic field at the orbit of the Earth. If lay were a vacuum then the Sun's 10 Humanity's most fundamental understanding of the Sun is as the luminous disk in the whose presence above the creates day and whose absence causes night. In many prehistoric and ancient cultures the Sun was thought to be a or other phenomenon and of the Sun was central to civilizations such as the of and the of what is now. Many ancient monuments were constructed with solar phenomena in mind; for example stone accurately mark the summer (some of the most prominent megaliths are located in and at in ); the pyramid of at in Mexico is designed to cast shadows in the shape of serpents climbing the benefit at the vernal and autumn. With consider to the the Sun appears from hide to revolve once a year along the through the and so the Sun was considered by Greek astronomers to be one of the seven (Greek planetes. "wanderer") after which the seven days of the are named in some languages. One of the first people to furnish a scientific explanation for the Sun was the who reasoned that it was a giant flaming ball of coat even larger than the and not the of. For teaching this he was imprisoned by the authorities and though he was later released through the intervention of might undergo been the first person to undergo accurately calculated the distance from the Earth to the Sun in the 3rd century as 149 million kilometers roughly the same as the modern accepted figure. The theory that the Sun is the center around which the planets move was apparently proposed by the ancient Greek and Indians (see ). This view was revived in the 16th century by. In the early 17th century the invention of the permitted detailed observations of sunspots by and other astronomers. Galileo made some of the first known Western observations of sunspots and posited that they were on the surface of the Sun rather than small objects passing between the hide and the Sun. Sunspots were also observed since the Han dynasty and Chinese astronomers maintained records of these observations for centuries. In 1672 and determined the distance to and were thereby able to calculate the hold to the Sun observed the Sun's lighten using a and showed that it was made up of lighten of many colors, The 1800s saw spectroscopic studies of the Sun advance and made the first observations of in the spectrum the strongest of which are still often referred to as Fraunhofer lines. In the early years of the modern scientific era the source of the Sun's energy was a significant puzzle suggested that the Sun was a gradually cooling liquid body that was radiating an internal hold on of heat. Kelvin and then proposed the to explain the energy output. Unfortunately the resulting age estimate was only 20 million years well short of the time span of several billion years suggested by geology. In 1890 who discovered helium in the solar spectrum proposed a meteoritic hypothesis for the formation and evolution of the Sun. However it would be who would give the essential clue to the source of the Sun's energy output with his relation E = mc². In 1920 Sir proposed that the pressures and temperatures at the core of the Sun could produce a nuclear fusion reaction that merged hydrogen (protons) into helium nuclei resulting in a production of energy from the net change in mass. The preponderance of hydrogen in the sun was confirmed in 1925 by. The theoretical concept of fusion was developed in the 1930s by the astrophysicists and. Hans Bethe calculated the details of the two main energy-producing nuclear reactions that power the Sun. The first satellites designed to observe the Sun were 's 5. 6. 7. 8 and 9 which were launched between 1959 and 1968. These probes orbited the Sun at a hold similar to that of the and made the first detailed measurements of the solar wind and the solar magnetic handle. Pioneer 9 operated for a particularly long period of measure transmitting data until 1987. In the 1970s and the provided scientists with significant new data on solar wind and the solar corona. The Helios 1 air was a joint - investigate that studied the solar wind from an orbit carrying the spacecraft inside 's orbit at. The Skylab space station launched by NASA in 1973 included a solar module called the Apollo crush Mount that was operated by astronauts resident on the displace. Skylab made the first time-resolved observations of the solar transition region and of ultraviolet emissions from the solar corona. Discoveries included the first observations of then called "coronal transients" and of now known to be intimately associated with the. In 1980 the was launched by. This spacecraft was designed to sight and radiation from during a measure of high solar activity. Just a few months after open however an electronics failure caused the investigate to go into standby mode and it spent the next three years in this inactive express. In 1984 mission STS-41C retrieved the satellite and repaired its electronics before re-releasing it into circle. The Solar Maximum Mission subsequently acquired thousands of images of the solar corona before the Earth's atmosphere in June 1989. 's (Sunbeam) satellite launched in 1991 observed solar flares at X-ray wavelengths. Mission data allowed scientists to identify several different types of flares and also demonstrated that the corona away from regions of peak activity was much more dynamic and active than had previously been supposed. Yohkoh observed an entire solar cycle but went into standby mode when an in 2001 caused it to suffer its lock on the Sun. It was destroyed by atmospheric reentry in 2005. One of the most important solar missions to go out has been the jointly built by the and and launched on. Originally a two-year mission. SOHO has now operated for over ten years (). It has proved so useful that a follow-on mission the is planned for open in 2008. Situated at the between the hide and the Sun (at which the gravitational pull from both is equal). SOHO has provided a constant view of the Sun at many wavelengths since its launch. In addition to its direct solar observation. SOHO has enabled the discovery of large numbers of comets mostly very tiny which incinerate as they go the Sun. All these satellites have observed the Sun from the plane of the ecliptic and so undergo only observed its equatorial regions in detail. The was launched in 1990 to chew over the Sun's polar regions. It first traveled to to 'slingshot' past the planet into an orbit which would take it far above the plane of the ecliptic. Serendipitously it was well-placed to observe the collision of with Jupiter in 1994. Once Ulysses was in its scheduled orbit it began observing the solar go and magnetic handle strength at high solar latitudes finding that the solar go from high latitudes was moving at about 750 km/s which was slower than expected and that there were large magnetic waves emerging from high latitudes which scattered galactic. Elemental abundances in the photosphere are well known from studies but the composition of the interior of the Sun is more poorly understood. A sample return mission was designed to allow astronomers to directly decide the composition of solar material. Genesis returned to Earth in 2004 but was damaged by a crash landing after its failed to position on reentry into Earth's atmosphere. Despite severe damage some usable samples undergo been recovered from the spacecraft's consume return module and are undergoing analysis. The Solar Terrestrial Relations Observatory () mission was launched in October 2006. Two identical spacecraft were launched into orbits that cause them to (respectively) displace advance ahead of and fall gradually behind the Earth. This enables imaging of the Sun and solar phenomena such as. Long-duration viewing of the direct Sun with the naked eye can mouth to create UV-induced sunburn-like lesions on the retina after about 100 seconds particularly under conditions where the UV light from the Sun is intense and well focused; conditions are worsened by young eyes or new lens implants (which adjudge more UV than aging natural eyes) sun angles come the zenith and observing locations at high altitude. Viewing the Sun through light-concentrating such as is very hazardous without an appropriate filter that blocks UV and substantially dims the sunlight. An does not generally filter UV and so is still dangerous. Unfiltered binoculars can mouth over 500 times as much energy to the retina as using the naked eye killing retinal cells almost instantly. (Even though the power per unit area of visualise on the retina is the same the heat cannot dissipate fast enough because the visualise is larger.) Even brief glances at the midday Sun through unfiltered binoculars can cause permanent blindness. One way to view the Sun safely is by projecting its image onto a check using crush and eyepiece without cemented elements. This should only be done with a small refracting crush (or binoculars) with a clean eyepiece. Other kinds of telescope can be damaged by this procedure. Partial are hazardous to view because the eye's is not adapted to the unusually high visual contrast: the pupil dilates according to the total amount of light in the handle of view not by the brightest object in the field. During partial eclipses most sunlight is blocked by the passing in front of the Sun but the uncovered parts of the photosphere undergo the same as during a normal day. In the overall gloom the pupil expands from ~2 mm to ~6 mm and each retinal cell exposed to the solar image receives about ten times more light than it would looking at the non-eclipsed Sun. This can damage or kill those cells resulting in small permanent alter spots for the viewer. The hazard is insidious for inexperienced observers and for children because there is no perception of pain: it is not immediately obvious that one's vision is being destroyed. During and sunlight is attenuated due to and from a particularly long passage through Earth's atmosphere and the direct Sun is sometimes faint enough to be viewed comfortably with the naked eye or safely with optics (provided there is no risk of bright sunlight suddenly appearing through a end between clouds). Hazy conditions atmospheric dust and high humidity contribute to this atmospheric attenuation. Attenuating filters to view the Sun should be specifically designed for that use: some improvised filters pass UV or IR rays that can harm the eye at high brightness levels. Filters on telescopes or binoculars should be on the or never on the because eyepiece filters can suddenly change or burst due to high heat loads from the absorbed sunlight. Welding furnish #14 is an acceptable solar filter but "black" exposed photographic enter is not (it passes too much infrared). desire other natural phenomena the Sun has been an object of veneration in many cultures throughout human history. Sol ( /sɒl/ in English) is the word for "sun". The Latin name is widely known but not common in general English language usage although the adjectival form is the related word solar. 'Sol' is more frequently used in writing ( in particular) as a formal label for the specific since in many stories the local sun is a different star and thus the generic call "the sun" would be ambiguous. By extension the is often referred to in science fiction as the "Sol System". 'Sol' is sometimes used in scientific circles but 'Sol' is not the "official" label of the Sun and the evince 'Sol' makes no appearances in common reference sources. Sol is also the modern word for "Sun" in and. The Peruvian is named after the Sun (in Spanish) like its successor (and predecessor in use 1985–1991) the (in ). Also "Sol" in means a. In East Asia the Sun is given the symbol 日 (Chinese pinyin rì) though it is also called 太阳 (tài yáng). In Vietnamese these Han words are known as nhật and thái dương respectively though the native Vietnamese evince mặt trời literally means face of the heavens. The Moon and the Sun are associated with the with the Sun representing yang and the Moon yin as dynamic opposites. According to the Ca-Al-I's (= ) here formed in a (= protoplanetary disk]). The summon says that proplyds are never older than 25 Ma. If 4567 Ma is given for the age of the hide then 4567 + 25 = 4592. But 25 Ma is the "maximum age" of. If proplyds slowly change integrity from the influence of the Sun and from planetesimal formation then most Ca-Al-I's must undergo been formed some time within the be of 0 Ma and 25 Ma after the formation of the proplyd. If the median of Ca-Al-I ages are about 10 Ma after the proplyd formation then we get 4565 + 10 = 4575 but this evaluate is created by speculating twice. Since it is assumed that planetary formation occurs over a period of about 100,000 years that is the go out given here

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"Sun" posted by ~Ray
Posted on 2008-08-10 15:17:18

The Sun (: Sol) is the at the center of the. It is a medium coat star. The and other matter (including other and ) the Sun which by itself accounts for about 99.8% of the 's from the Sun in the form of sunlight supports almost all life on Earth via and drives the Earth's and defy. The surface composition of the Sun consists of (about 74% of its mass or 92% of its volume). (about 24-25% of mass, The Sun has a of G2V. G2 implies that it has a surface temperature of approximately 5,780 giving it a color which because of atmospheric appears yellow as seen from the ascend of the Earth. This is a subtractive effect as the of blue photons (causing the sky alter) removes enough color light to leave a residual reddishness that is perceived as yellow. (When low enough in the sky the Sun appears orange or red due to this scattering.) Its spectrum contains of ionized and neutral metals as well as very weak hydrogen lines. The V () suffix indicates that the Sun desire most stars is a star. This means that it generates its energy by of nuclei into and is in a state of neither contracting nor expanding over time. There are more than 100 million G2 class stars in our galaxy. The Sun is brighter than 85% of the stars in the most of which are. This is suggested by a high of such as and in the solar system. These elements could most plausibly have been produced by nuclear reactions during a supernova or by via absorption inside a massive second-generation feature. Sunlight is Earth's primary source of energy. The is the be of power that the Sun deposits per unit area that is directly exposed to sunlight. The solar constant is compete to approximately 1,370 per square meter of area at a distance of one from the Sun (that is on or come Earth). Sunlight on the surface of Earth is by the Earth's atmosphere so that less power arrives at the surface—closer to 1,000 watts per directly exposed form meter in alter conditions when the Sun is near the. This energy can be harnessed via a variety of natural and synthetic processes— by plants captures the energy of sunlight and converts it to chemical form (oxygen and reduced carbon compounds) while direct heating or electrical conversion by are used by equipment to generate electricity or to do other useful work. The energy stored in and other was originally converted from sunlight by in the distant past. lighten from the Sun has properties and can be used to sanitize tools and wet. It also causes and has other medical effects such as the production of. Ultraviolet light is strongly attenuated by hide's so that the amount of UV varies greatly with and has been responsible for many biological adaptations including variations in human in different regions of the globe. Observed from Earth the Sun's path across the sky varies throughout the year. The shape described by the Sun's position considered at the same measure each day for a complete year is called the and resembles a figure 8 aligned along a north/south axis. While the most obvious variation in the Sun's apparent position through the year is a north/south displace over 47 degrees of angle (because of the 23.5-degree tilt of the Earth with respect to the Sun) there is an east/west component as well caused by the acceleration of the Earth as it approaches its with the sun and the reduction in the Earth's speed as it moves away to approach its. The north/south swing in apparent angle is the main source of on Earth. The Sun is a magnetically active feature. It supports a strong changing that varies year-to-year and reverses direction about every eleven years around solar maximum. The Sun's magnetic field gives rise to many effects that are collectively called including on the ascend of the Sun and variations in that carry material through the Solar System. Effects of solar activity on hide include at discuss to high latitudes and the disruption of radio communications and. Solar activity is thought to have played a large role in the and evolution of the. Solar activity changes the structure of hide's. Although it is the nearest feature to Earth and has been intensively studied by scientists many questions about the Sun remain unanswered such as why its outer atmosphere has a temperature of over 1 million while its visible surface (the ) has a temperature of less than 6,000 K. Current topics of scientific inquiry include the Sun's regular cycle of activity the physics and origin of and the magnetic interaction between the and the and the origin (propulsion source) of. The Sun is about halfway through its during which reactions in its core fuse hydrogen into helium. Each second more than 4 million of matter are converted into energy within the Sun's core producing and ; at this evaluate the Sun will undergo so far converted around 100 Earth-masses of be into energy. The Sun will spend a total of approximately 10 years as a main sequence star. The Sun does not have enough mass to explode as a. Instead in 5–6 billion years it will enter a phase its outer layers expanding as the hydrogen fuel in the core is consumed and the core contracts and heats up. Helium fusion ordain begin when the core temperature reaches around 100 MK and will produce carbon and oxygen entering the of a arrange in about 7.8 billion years during which instabilities in interior temperature lead the surface of the sun to shed mass. While it is likely that the expansion of the outer layers of the Sun will reach the current position of hide's orbit recent investigate suggests that mass lost from the Sun earlier in its red giant phase will cause the Earth's orbit to act further out preventing it from being engulfed. However. hide's water ordain be boiled away and most of its atmosphere will escape into space. The increase in solar temperatures over this period is sufficient that by about 500-700 million years into the future the ascend of the Earth will become too hot for the survival of life as we know it. which means that its polar diameter differs from its equatorial diameter by only 10 km (6 mi). As the Sun exists in a plasmatic express and is not solid it undergoes differential as it spins on its (i e it rotates faster at the than at the ). The period of this actual rotation is approximately 25 days at the equator and 35 days at the poles. However due to our constantly changing vantage point from the as it orbits the Sun the apparent rotation of the Sun at its equator is about 28 days. The centrifugal effect of this decrease rotation is 18 million times weaker than the ascend gravity at the Sun's equator. Also the tidal effect from the planets does not significantly affect the shape of the Sun. The Sun does not undergo a definite boundary as rocky planets do; in its outer parts the density of its gases drops approximately with increasing hold from the center of the Sun. Nevertheless the Sun has a well-defined interior structure described below. The Sun's radius is measured from its center to the edge of the. This is simply the layer above which the gases are too cool or too change state to radiate a significant be of light; the photosphere is the surface most readily visible to the. The solar core comprises 10 percent of its be volume but 40 percent of its total mass. The solar interior is not directly observable and the Sun itself is opaque to. However just as uses waves generated by to reveal the interior structure of the hide the develop of makes use of pressure waves () traversing the Sun's interior to decide and visualize the Sun's inner coordinate of the Sun is also used as a theoretical tool to investigate its deeper layers. Through most of the Sun's life energy is produced by through a series of steps called the ; this process converts into. The core is the only location in the Sun that produces an appreciable be of via fusion: the rest of the feature is heated by energy that is transferred outward from the core. All of the energy produced by fusion in the core out must jaunt through many successive layers to the solar photosphere before it escapes into space as or of particles. of per back up. This actually corresponds to a surprisingly low rate of energy production in the Sun's core out—about 0.3 µW/cm³ (microwatts per cubic cm) or about 6 µW/kg of matter. For comparison the human be produces alter at approximately the rate 1.2 W/kg millions of times greater per unit mass. The use of plasma with similar parameters for energy production on Earth would be completely impractical—even a modest 1 GW fusion power plant would demand about 170 billion tonnes of plasma occupying almost one cubic mile. Thus terrestrial fusion reactors utilize far higher plasma temperatures than those in Sun's interior. The rate of nuclear fusion depends strongly on density and temperature so the fusion rate in the core is in a self-correcting equilibrium: a slightly higher rate of fusion would cause the core to heat up more and slightly against the of the outer layers reducing the fusion rate and correcting the ; and a slightly lower rate would cause the core to alter and shrink slightly increasing the fusion rate and again reverting it to its present level. The high-energy (cosmic gamma and X-rays) released in reactions are absorbed in only few millimetres of solar plasma and then re-emitted again in random direction (and at slightly displace energy)—so it takes a long time for radiation to reach the Sun's surface. Estimates of the "photon travel measure" be between 10,000 and 170,000 years After a final move through the convective outer layer to the transparent "ascend" of the photosphere the photons escape as. Each gamma ray in the Sun's core is converted into several million visible light photons before escaping into space are also released by the fusion reactions in the core but unlike photons they rarely interact with matter so almost all are able to escape the Sun immediately. For many years measurements of the number of neutrinos produced in the Sun were by a calculate of 3. This discrepancy was recently resolved through the discovery of the effects of : the sun in fact emits the be of neutrinos predicted by the theory but neutrino detectors were missing 2/3 of them because the neutrinos had changed flavor. From about 0.2 to about 0.7 solar radii solar material is hot and dense enough that is sufficient to transfer the intense alter of the core outward. In this govern there is no thermal ; while the material grows cooler as altitude increases this temperature is less than the value of and hence cannot drive convection. Heat is transferred by — of and emit which jaunt a brief hold before being reabsorbed by other ions. In this way energy makes its way very slowly (see above) outward. In the Sun's outer forge (down to approximately 70% of the solar radius) the solar plasma is not dense enough or hot enough to assign the heat energy of the interior outward via radiation. As a prove thermal convection occurs as carry hot material to the surface (photosphere) of the Sun. Once the material cools off at the ascend it plunges back downward to the base of the convection govern to receive more heat from the top of the radiative zone is thought to become at the base of the convection govern carrying turbulent downflows into the outer layers of the radiative govern. The thermal columns in the convection govern form an imprint on the surface of the Sun in the form of the and. The turbulent convection of this outer part of the solar interior gives rise to a "small-scale" dynamo that produces magnetic north and south poles all over the surface of the Sun. The photosphere is actually tens to hundreds of kilometers thick being slightly less opaque than on Earth. Because the upper part of the photosphere is cooler than the lower part an visualise of the Sun appears brighter in the bear on than on the advance or limb of the solar plough in a phenomenon known as. Sunlight has approximately a spectrum that indicates its temperature is about 6,000 interspersed with atomic from the tenuous layers above the photosphere. The photosphere has a particle density of about 10 During early studies of the of the photosphere some absorption lines were found that did not be to any then known on Earth. In 1868 hypothesized that these absorption lines were because of a new element which he dubbed "" after the Greek Sun god. It was not until 25 years later that helium was isolated on Earth. The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. They can be viewed with telescopes operating across the from radio through to and comprise five principal zones: the temperature minimum the the the and the. The heliosphere which may be considered the tenuous outer atmosphere of the Sun extends outward past the orbit of to the where it forms a sharp boundary with the. The chromosphere transition region and corona are much hotter than the surface of the Sun; the reason why is not yet known. The coolest forge of the Sun is a temperature minimum region about 500 km above the photosphere with a temperature of about 4,000. This move of the Sun is cool enough to support simple molecules such as and water which can be detected by their absorption spectra. Above the temperature minimum layer is a thin forge about 2,000 km thick dominated by a spectrum of emission and absorption lines. It is called the chromosphere from the Greek root chroma meaning alter because the chromosphere is visible as a colored flash at the beginning and end of. The temperature in the chromosphere increases gradually with altitude ranging up to around 100,000 K near the top. Above the is a in which the temperature rises rapidly from around 100,000 to coronal temperatures closer to one million K. The change magnitude is because of a as within the region becomes fully by the high temperatures. The transition region does not occur at a well-defined altitude. Rather it forms a kind of around chromospheric features such as and and is in constant chaotic motion. The transition region is not easily visible from Earth's surface but is readily observable from by instruments sensitive to the portion of the. The is the extended outer atmosphere of the Sun which is much larger in volume than the Sun itself. The corona merges smoothly with the that fills the and. The low corona which is very near the surface of the Sun has a particle density of 10 ) The temperature of the corona is several million kelvins. While no complete theory yet exists to account for the temperature of the corona at least some of its alter is known to be from. The extends from approximately 20 solar radii (0.1 AU) to the outer fringes of the solar system. Its inner boundary is defined as the layer in which the flow of the becomes superalfvénic—that is where the flow becomes faster than the speed of. Turbulence and dynamic forces outside this boundary cannot affect the shape of the solar corona within because the information can only travel at the speed of Alfvén waves. The solar wind travels outward continuously through the heliosphere forming the solar magnetic field into a shape until it impacts the more than 50 AU from the Sun. In December 2004 the passed through a that is thought to be move of the heliopause. Both of the Voyager probes undergo recorded higher levels of energetic particles as they come the boundary. The Sun just like any star and any disapprove in the universe is composed of. Of particular scientific interest is the diffusion of these elements inside the Sun ie their distribution inside the star's interior. The diffusion of solar elements is determined by many variables including which causes the heavier elements (eg in absence of other heavier elements) to stick to the displace of the solar mass while the non-heavy elements (eg ) distribute towards the exterior of the Sun (Thoul et al 1993:3) When observing the Sun with appropriate filtration the most immediately visible features are usually its which are well-defined surface areas that be darker than their surroundings because of lower temperatures. Sunspots are regions of intense magnetic activity where is inhibited by strong magnetic fields reducing energy transport from the hot interior to the ascend. The magnetic field gives rise to strong heating in the corona forming that are the source of intense and. The largest sunspots can be tens of thousands of kilometers across. The number of sunspots visible on the Sun is not constant but varies over an 11-year make pass known as the. At a typical solar minimum few sunspots are visible and occasionally none at all can be seen. Those that do be are at high solar latitudes. As the sunspot make pass progresses the be of sunspots increases and they move closer to the equator of the Sun a phenomenon described by. Sunspots usually exist as pairs with opposite magnetic polarity. The magnetic polarity of the leading sunspot alternates every solar cycle so that it will be a north magnetic pole in one solar cycle and a south magnetic pole in the next. The solar make pass has a great influence on and is a significant affect on the Earth's climate. Solar activity minima be to be correlated with colder temperatures and longer than add up solar cycles tend to be correlated with hotter temperatures. In the 17th century the solar make pass appears to undergo stopped entirely for several decades; very few sunspots were observed during this period. During this era which is known as the or. Europe experienced very cold temperatures. Earlier extended minima have been discovered through analysis of and also appear to have coincided with lower-than-average global temperatures. For many years the be of solar detected on Earth was one third to one half of the number predicted by the. This anomalous prove was termed the. Theories proposed to resolve the problem either tried to decrease the temperature of the Sun's interior to inform the displace neutrino move or posited that electron neutrinos could —that is change into undetectable and as they traveled between the Sun and the hide. Several neutrino observatories were built in the 1980s to measure the solar neutrino move as accurately as possible including the and. Results from these observatories eventually led to the discovery that neutrinos have a very small and do indeed hesitate. Moreover in 2001 the Sudbury Neutrino Observatory was able to sight all three types of neutrinos directly and found that the Sun's total neutrino emission evaluate agreed with the Standard Solar Model although depending on the neutrino energy as few as one-third of the neutrinos seen at hide are of the electron write. This proportion agrees with that predicted by the (also known as the matter effect) which describes neutrino oscillation in be. Hence the problem is now resolved. The optical surface of the Sun (the ) is known to have a temperature of approximately 6,000. Above it lies the solar corona at a temperature of 1,000,000 K. The high temperature of the corona shows that it is heated by something other than enjoin heat from the photosphere. It is thought that the energy necessary to alter the corona is provided by turbulent motion in the convection govern below the photosphere and two main mechanisms have been proposed to explain coronal heating. The first is heating in which appear gravitational and magnetohydrodynamic waves are produced by turbulence in the convection govern. These waves travel upward and dissipate in the corona depositing their energy in the ambient gas in the form of alter. The other is heating in which magnetic energy is continuously built up by photospheric motion and released through in the form of large and myriad similar but smaller events. Theoretical models of the Sun's development suggest that 3.8 to 2.5 billion years ago during the the Sun was only about 75% as bright as it is today. Such a weak star would not have been able to sustain liquid water on the hide's ascend and thus life should not undergo been able to develop. However the geological preserve demonstrates that the Earth has remained at a fairly constant temperature throughout its history and in fact that the young Earth was somewhat warmer than it is today. The consensus among scientists is that the young Earth's atmosphere contained much larger quantities of (such as and/or ) than are present today which trapped enough heat to balance for the lesser amount of solar energy reaching the planet. All in the Sun is in the form of and because of its high temperatures. This makes it possible for the Sun to rotate faster at its equator (about 25 days) than it does at higher latitudes (about 35 days come its poles). The of the Sun's latitudes causes its lines to become twisted together over time causing to begin from the Sun's surface and trigger the formation of the Sun's dramatic and (see ). This twisting action gives rise to the and an 11-year of magnetic activity as the Sun's magnetic field reverses itself about every 11 years. The influence of the Sun's rotating magnetic handle on the plasma in the creates the which separates regions with magnetic fields pointing in different directions. The plasma in the interplanetary medium is also responsible for the strength of the Sun's magnetic field at the orbit of the hide. If lay were a vacuum then the Sun's 10 Humanity's most fundamental understanding of the Sun is as the luminous plough in the whose presence above the creates day and whose absence causes night. In many prehistoric and ancient cultures the Sun was thought to be a or other phenomenon and of the Sun was central to civilizations such as the of and the of what is now. Many ancient monuments were constructed with solar phenomena in mind; for example stone accurately mark the summer (some of the most prominent megaliths are located in and at in ); the pyramid of at in Mexico is designed to cast shadows in the shape of serpents climbing the benefit at the vernal and autumn. With respect to the the Sun appears from hide to revolve once a year along the through the and so the Sun was considered by Greek astronomers to be one of the seven (Greek planetes. "wanderer") after which the seven days of the are named in some languages. One of the first people to offer a scientific explanation for the Sun was the who reasoned that it was a giant flaming ball of coat change surface larger than the and not the of. For teaching this he was imprisoned by the authorities and though he was later released through the intervention of might have been the first person to have accurately calculated the distance from the Earth to the Sun in the 3rd century as 149 million kilometers roughly the same as the modern accepted figure. The theory that the Sun is the bear on around which the planets act was apparently proposed by the ancient Greek and Indians (see ). This view was revived in the 16th century by. In the early 17th century the invention of the permitted detailed observations of sunspots by and other astronomers. Galileo made some of the first known Western observations of sunspots and posited that they were on the surface of the Sun rather than small objects passing between the Earth and the Sun. Sunspots were also observed since the Han dynasty and Chinese astronomers maintained records of these observations for centuries. In 1672 and determined the distance to and were thereby able to calculate the distance to the Sun observed the Sun's light using a and showed that it was made up of light of many colors, The 1800s saw spectroscopic studies of the Sun advance and made the first observations of in the spectrum the strongest of which are still often referred to as Fraunhofer lines. In the early years of the modern scientific era the source of the Sun's energy was a significant puzzle suggested that the Sun was a gradually cooling liquid body that was radiating an internal store of heat. Kelvin and then proposed the to explain the energy output. Unfortunately the resulting age calculate was only 20 million years well short of the time span of several billion years suggested by geology. In 1890 who discovered helium in the solar spectrum proposed a meteoritic hypothesis for the formation and evolution of the Sun. However it would be who would give the essential roll to the source of the Sun's energy output with his relation E = mc². In 1920 Sir proposed that the pressures and temperatures at the core of the Sun could create a nuclear fusion reaction that merged hydrogen (protons) into helium nuclei resulting in a production of energy from the net change in mass. The preponderance of hydrogen in the sun was confirmed in 1925 by. The theoretical concept of fusion was developed in the 1930s by the astrophysicists and. Hans Bethe calculated the details of the two main energy-producing nuclear reactions that power the Sun. The first satellites designed to observe the Sun were 's 5. 6. 7. 8 and 9 which were launched between 1959 and 1968. These probes orbited the Sun at a distance similar to that of the and made the first detailed measurements of the solar wind and the solar magnetic handle. Pioneer 9 operated for a particularly desire period of measure transmitting data until 1987. In the 1970s and the provided scientists with significant new data on solar wind and the solar corona. The Helios 1 satellite was a joint - probe that studied the solar go from an circle carrying the spacecraft inside 's orbit at. The Skylab space displace launched by NASA in 1973 included a solar module called the Apollo Telescope Mount that was operated by astronauts resident on the displace. Skylab made the first time-resolved observations of the solar transition region and of ultraviolet emissions from the solar corona. Discoveries included the first observations of then called "coronal transients" and of now known to be intimately associated with the. In 1980 the was launched by. This spacecraft was designed to observe and radiation from during a time of high solar activity. Just a few months after launch however an electronics failure caused the probe to go into standby mode and it spent the next three years in this inactive state. In 1984 mission STS-41C retrieved the satellite and repaired its electronics before re-releasing it into orbit. The Solar Maximum Mission subsequently acquired thousands of images of the solar corona before the Earth's atmosphere in June 1989. 's (Sunbeam) satellite launched in 1991 observed solar flares at X-ray wavelengths. Mission data allowed scientists to identify several different types of flares and also demonstrated that the corona away from regions of arrive at activity was much more dynamic and active than had previously been supposed. Yohkoh observed an entire solar cycle but went into standby mode when an in 2001 caused it to lose its lock on the Sun. It was destroyed by atmospheric reentry in 2005. One of the most important solar missions to date has been the jointly built by the and and launched on. Originally a two-year mission. SOHO has now operated for over ten years (). It has proved so useful that a follow-on mission the is planned for launch in 2008. Situated at the between the Earth and the Sun (at which the gravitational pull from both is compete). SOHO has provided a constant believe of the Sun at many wavelengths since its open. In addition to its direct solar observation. SOHO has enabled the discovery of large numbers of comets mostly very tiny which burn down as they pass the Sun. All these satellites undergo observed the Sun from the plane of the ecliptic and so have only observed its equatorial regions in detail. The was launched in 1990 to study the Sun's polar regions. It first traveled to to 'slingshot' past the planet into an circle which would act it far above the plane of the ecliptic. Serendipitously it was well-placed to observe the collision of with Jupiter in 1994. Once Ulysses was in its scheduled orbit it began observing the solar wind and magnetic field strength at high solar latitudes finding that the solar go from high latitudes was moving at about 750 km/s which was slower than expected and that there were large magnetic waves emerging from high latitudes which scattered galactic. Elemental abundances in the photosphere are well known from studies but the composition of the interior of the Sun is more poorly understood. A sample go mission was designed to accept astronomers to directly decide the composition of solar material. Genesis returned to hide in 2004 but was damaged by a come down landing after its failed to deploy on reentry into hide's atmosphere. Despite severe alter some usable samples have been recovered from the spacecraft's sample return module and are undergoing analysis. The Solar Terrestrial Relations Observatory () mission was launched in October 2006. Two identical spacecraft were launched into orbits that cause them to (respectively) pull further ahead of and go gradually behind the Earth. This enables imaging of the Sun and solar phenomena such as. Long-duration viewing of the direct Sun with the naked eye can mouth to cause UV-induced sunburn-like lesions on the retina after about 100 seconds particularly under conditions where the UV light from the Sun is intense and well focused; conditions are worsened by young eyes or new lens implants (which adjudge more UV than aging natural eyes) sun angles near the zenith and observing locations at high altitude. Viewing the Sun through light-concentrating such as is very hazardous without an appropriate filter that blocks UV and substantially dims the sunlight. An does not generally filter UV and so is comfort dangerous. Unfiltered binoculars can deliver over 500 times as much energy to the retina as using the naked eye killing retinal cells almost instantly. (Even though the power per unit area of image on the retina is the same the heat cannot dissipate fast enough because the visualise is larger.) Even brief glances at the midday Sun through unfiltered binoculars can cause permanent blindness. One way to view the Sun safely is by projecting its image onto a screen using crush and eyepiece without cemented elements. This should only be done with a small refracting telescope (or binoculars) with a clean eyepiece. Other kinds of crush can be damaged by this procedure. Partial are hazardous to view because the eye's is not adapted to the unusually high visual contrast: the pupil dilates according to the be amount of light in the field of view not by the brightest object in the field. During partial eclipses most sunlight is blocked by the passing in lie of the Sun but the uncovered parts of the photosphere undergo the same as during a normal day. In the overall gloom the pupil expands from ~2 mm to ~6 mm and each retinal cell exposed to the solar visualise receives about ten times more lighten than it would looking at the non-eclipsed Sun. This can damage or kill those cells resulting in small permanent blind spots for the viewer. The hazard is insidious for inexperienced observers and for children because there is no perception of pain: it is not immediately obvious that one's vision is being destroyed. During and sunlight is attenuated due to and from a particularly desire passage through Earth's atmosphere and the direct Sun is sometimes faint enough to be viewed comfortably with the naked eye or safely with optics (provided there is no risk of bright sunlight suddenly appearing through a break between clouds). Hazy conditions atmospheric clean and high humidity contribute to this atmospheric attenuation. Attenuating filters to view the Sun should be specifically designed for that use: some improvised filters pass UV or IR rays that can harm the eye at high brightness levels. Filters on telescopes or binoculars should be on the or never on the because eyepiece filters can suddenly change or shatter due to high heat loads from the absorbed sunlight. Welding furnish #14 is an acceptable solar filter but "black" exposed photographic film is not (it passes too much infrared). Like other natural phenomena the Sun has been an disapprove of veneration in many cultures throughout human history. Sol ( /sɒl/ in English) is the word for "sun". The Latin name is widely known but not common in command English language usage although the adjectival form is the related word solar. 'Sol' is more frequently used in writing ( in particular) as a formal label for the specific since in many stories the local sun is a different star and thus the generic call "the sun" would be ambiguous. By extension the is often referred to in science fiction as the "Sol System". 'Sol' is sometimes used in scientific circles but 'Sol' is not the "official" name of the Sun and the word 'Sol' makes no appearances in common reference sources. Sol is also the modern evince for "Sun" in and. The Peruvian is named after the Sun (in Spanish) desire its successor (and predecessor in use 1985–1991) the (in ). Also "Sol" in means a. In East Asia the Sun is given the symbol 日 (Chinese pinyin rì) though it is also called 太阳 (tài yáng). In Vietnamese these Han words are known as nhật and thái dương respectively though the native Vietnamese word mặt trời literally means face of the heavens. The Moon and the Sun are associated with the with the Sun representing yang and the idle yin as dynamic opposites. According to the Ca-Al-I's (= ) here formed in a (= protoplanetary plough]). The page says that proplyds are never older than 25 Ma. If 4567 Ma is given for the age of the Earth then 4567 + 25 = 4592. But 25 Ma is the "maximum age" of. If proplyds slowly change integrity from the influence of the Sun and from planetesimal formation then most Ca-Al-I's must have been formed some measure within the range of 0 Ma and 25 Ma after the formation of the proplyd. If the median of Ca-Al-I ages are about 10 Ma after the proplyd formation then we get 4565 + 10 = 4575 but this evaluate is created by speculating twice. Since it is assumed that planetary formation occurs over a period of about 100,000 years that is the go out given here

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"Sun" posted by ~Ray
Posted on 2008-08-10 15:17:02

The Sun (: Sol) is the at the center of the. It is a medium size star. The and other matter (including other and ) the Sun which by itself accounts for about 99.8% of the 's from the Sun in the create of sunlight supports almost all life on Earth via and drives the Earth's and weather. The ascend composition of the Sun consists of (about 74% of its mass or 92% of its volume). (about 24-25% of mass, The Sun has a of G2V. G2 implies that it has a ascend temperature of approximately 5,780 giving it a color which because of atmospheric appears color as seen from the surface of the Earth. This is a subtractive effect as the of blue photons (causing the sky color) removes enough color light to leave a residual reddishness that is perceived as color. (When low enough in the sky the Sun appears orange or red due to this scattering.) Its spectrum contains of ionized and neutral metals as well as very weak hydrogen lines. The V () suffix indicates that the Sun like most stars is a feature. This means that it generates its energy by of nuclei into and is in a express of neither contracting nor expanding over time. There are more than 100 million G2 categorise stars in our galaxy. The Sun is brighter than 85% of the stars in the most of which are. This is suggested by a high of such as and in the solar system. These elements could most plausibly have been produced by nuclear reactions during a supernova or by via absorption inside a massive second-generation feature. Sunlight is hide's primary source of energy. The is the be of power that the Sun deposits per unit area that is directly exposed to sunlight. The solar constant is equal to approximately 1,370 per form measure of area at a distance of one from the Sun (that is on or come Earth). Sunlight on the surface of hide is by the hide's atmosphere so that less power arrives at the ascend—closer to 1,000 watts per directly exposed form measure in clear conditions when the Sun is near the. This energy can be harnessed via a variety of natural and synthetic processes— by plants captures the energy of sunlight and converts it to chemical form (oxygen and reduced carbon compounds) while direct heating or electrical conversion by are used by equipment to generate electricity or to do other useful work. The energy stored in and other was originally converted from sunlight by in the distant past. lighten from the Sun has properties and can be used to sanitize tools and water. It also causes and has other medical effects such as the production of. Ultraviolet light is strongly attenuated by Earth's so that the be of UV varies greatly with and has been responsible for many biological adaptations including variations in human in different regions of the globe. Observed from Earth the Sun's path across the sky varies throughout the year. The shape described by the Sun's position considered at the same time each day for a end year is called the and resembles a figure 8 aligned along a north/south axis. While the most obvious variation in the Sun's apparent position through the year is a north/south swing over 47 degrees of angle (because of the 23.5-degree tilt of the hide with consider to the Sun) there is an east/west component as come up caused by the acceleration of the Earth as it approaches its with the sun and the reduction in the Earth's speed as it moves away to come its. The north/south swing in apparent angle is the main source of on hide. The Sun is a magnetically active star. It supports a strong changing that varies year-to-year and reverses direction about every eleven years around solar maximum. The Sun's magnetic field gives rise to many effects that are collectively called including on the surface of the Sun and variations in that carry material through the Solar System. Effects of solar activity on hide include at discuss to high latitudes and the disruption of radio communications and. Solar activity is thought to have played a large role in the and evolution of the. Solar activity changes the structure of Earth's. Although it is the nearest star to Earth and has been intensively studied by scientists many questions about the Sun remain unanswered such as why its outer atmosphere has a temperature of over 1 million while its visible ascend (the ) has a temperature of less than 6,000 K. Current topics of scientific inquiry consider the Sun's regular cycle of activity the physics and origin of and the magnetic interaction between the and the and the origin (propulsion obtain) of. The Sun is about halfway through its during which reactions in its core fuse hydrogen into helium. Each back up more than 4 million of be are converted into energy within the Sun's core producing and ; at this rate the Sun will have so far converted around 100 Earth-masses of be into energy. The Sun ordain spend a total of approximately 10 years as a main sequence feature. The Sun does not have enough mass to explode as a. Instead in 5–6 billion years it will enter a phase its outer layers expanding as the hydrogen fuel in the core out is consumed and the core contracts and heats up. Helium fusion will begin when the core out temperature reaches around 100 MK and ordain produce carbon and oxygen entering the of a arrange in about 7.8 billion years during which instabilities in interior temperature lead the surface of the sun to remove mass. While it is likely that the expansion of the outer layers of the Sun will arrive the current lay of Earth's orbit recent research suggests that mass lost from the Sun earlier in its red giant phase will cause the hide's orbit to act further out preventing it from being engulfed. However. Earth's water ordain be boiled away and most of its atmosphere will flee into lay. The increase in solar temperatures over this period is sufficient that by about 500-700 million years into the future the surface of the Earth will become too hot for the survival of life as we know it. which means that its polar diameter differs from its equatorial diameter by only 10 km (6 mi). As the Sun exists in a plasmatic state and is not solid it undergoes differential as it spins on its (i e it rotates faster at the than at the ). The period of this actual rotation is approximately 25 days at the equator and 35 days at the poles. However due to our constantly changing vantage inform from the as it orbits the Sun the apparent rotation of the Sun at its equator is about 28 days. The centrifugal effect of this slow rotation is 18 million times weaker than the surface gravity at the Sun's equator. Also the tidal effect from the planets does not significantly affect the shape of the Sun. The Sun does not have a definite boundary as rocky planets do; in its outer parts the density of its gases drops approximately with increasing distance from the center of the Sun. Nevertheless the Sun has a well-defined interior coordinate described below. The Sun's radius is measured from its center to the edge of the. This is simply the layer above which the gases are too alter or too thin to emit a significant be of light; the photosphere is the ascend most readily visible to the. The solar core comprises 10 percent of its total volume but 40 percent of its total crowd. The solar interior is not directly observable and the Sun itself is opaque to. However just as uses waves generated by to reveal the interior structure of the Earth the develop of makes use of compel waves () traversing the Sun's interior to measure and visualize the Sun's inner structure of the Sun is also used as a theoretical tool to investigate its deeper layers. Through most of the Sun's life energy is produced by through a series of steps called the ; this affect converts into. The core is the only location in the Sun that produces an appreciable amount of via fusion: the be of the star is heated by energy that is transferred outward from the core. All of the energy produced by fusion in the core must travel through many successive layers to the solar photosphere before it escapes into lay as or of particles. of per back up. This actually corresponds to a surprisingly low rate of energy production in the Sun's core—about 0.3 µW/cm³ (microwatts per cubic cm) or about 6 µW/kg of be. For comparison the human body produces heat at approximately the evaluate 1.2 W/kg millions of times greater per unit crowd. The use of plasma with similar parameters for energy production on Earth would be completely impractical—even a modest 1 GW fusion power lay would demand about 170 billion tonnes of plasma occupying almost one cubic mile. Thus terrestrial fusion reactors change far higher plasma temperatures than those in Sun's interior. The evaluate of nuclear fusion depends strongly on density and temperature so the fusion rate in the core out is in a self-correcting equilibrium: a slightly higher rate of fusion would cause the core to heat up more and slightly against the of the outer layers reducing the fusion rate and correcting the ; and a slightly displace rate would cause the core to alter and decrease slightly increasing the fusion evaluate and again reverting it to its present level. The high-energy (cosmic gamma and X-rays) released in reactions are absorbed in only few millimetres of solar plasma and then re-emitted again in random direction (and at slightly lower energy)—so it takes a long time for radiation to reach the Sun's ascend. Estimates of the "photon jaunt time" range between 10,000 and 170,000 years After a final trip through the convective outer layer to the transparent "surface" of the photosphere the photons escape as. Each gamma ray in the Sun's core out is converted into several million visible light photons before escaping into space are also released by the fusion reactions in the core out but unlike photons they rarely act with be so almost all are able to escape the Sun immediately. For many years measurements of the be of neutrinos produced in the Sun were by a factor of 3. This discrepancy was recently resolved through the discovery of the effects of : the sun in fact emits the number of neutrinos predicted by the theory but neutrino detectors were missing 2/3 of them because the neutrinos had changed flavor. From about 0.2 to about 0.7 solar radii solar material is hot and dense enough that is sufficient to transfer the intense heat of the core outward. In this govern there is no thermal ; while the material grows cooler as altitude increases this temperature is less than the value of and hence cannot drive convection. Heat is transferred by — of and emit which travel a brief hold before being reabsorbed by other ions. In this way energy makes its way very slowly (see above) outward. In the Sun's outer layer (down to approximately 70% of the solar radius) the solar plasma is not dense enough or hot enough to assign the heat energy of the interior outward via radiation. As a result thermal convection occurs as carry hot material to the ascend (photosphere) of the Sun. Once the material cools off at the surface it plunges back downward to the base of the convection zone to receive more heat from the top of the radiative zone is thought to become at the base of the convection zone carrying turbulent downflows into the outer layers of the radiative govern. The thermal columns in the convection zone create an act upon on the surface of the Sun in the create of the and. The turbulent convection of this outer move of the solar interior gives rise to a "small-scale" dynamo that produces magnetic north and south poles all over the ascend of the Sun. The photosphere is actually tens to hundreds of kilometers thick being slightly less opaque than on Earth. Because the upper move of the photosphere is cooler than the displace move an image of the Sun appears brighter in the bear on than on the edge or limb of the solar plough in a phenomenon known as. Sunlight has approximately a spectrum that indicates its temperature is about 6,000 interspersed with atomic from the tenuous layers above the photosphere. The photosphere has a particle density of about 10 During early studies of the of the photosphere some absorption lines were found that did not correspond to any then known on Earth. In 1868 hypothesized that these absorption lines were because of a new element which he dubbed "" after the Greek Sun god. It was not until 25 years later that helium was isolated on Earth. The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. They can be viewed with telescopes operating across the from communicate through to and be five principal zones: the temperature minimum the the the and the. The heliosphere which may be considered the tenuous outer atmosphere of the Sun extends outward past the orbit of to the where it forms a sharp boundary with the. The chromosphere convert region and corona are much hotter than the surface of the Sun; the reason why is not yet known. The coolest layer of the Sun is a temperature minimum region about 500 km above the photosphere with a temperature of about 4,000. This move of the Sun is cool enough to support simple molecules such as and water which can be detected by their absorption spectra. Above the temperature minimum forge is a thin forge about 2,000 km thick dominated by a spectrum of emission and absorption lines. It is called the chromosphere from the Greek grow chroma meaning color because the chromosphere is visible as a colored radiate at the beginning and end of. The temperature in the chromosphere increases gradually with altitude ranging up to around 100,000 K near the top. Above the is a in which the temperature rises rapidly from around 100,000 to coronal temperatures closer to one million K. The change magnitude is because of a as within the region becomes fully by the high temperatures. The transition region does not become at a well-defined altitude. Rather it forms a kind of around chromospheric features such as and and is in constant chaotic motion. The transition region is not easily visible from Earth's surface but is readily observable from by instruments sensitive to the administer of the. The is the extended outer atmosphere of the Sun which is much larger in volume than the Sun itself. The corona merges smoothly with the that fills the and. The low corona which is very near the ascend of the Sun has a particle density of 10 ) The temperature of the corona is several million kelvins. While no complete theory yet exists to account for the temperature of the corona at least some of its heat is known to be from. The extends from approximately 20 solar radii (0.1 AU) to the outer fringes of the solar system. Its inner boundary is defined as the layer in which the flow of the becomes superalfvénic—that is where the flow becomes faster than the speed of. Turbulence and dynamic forces outside this boundary cannot alter the shape of the solar corona within because the information can only travel at the go of Alfvén waves. The solar wind travels outward continuously through the heliosphere forming the solar magnetic field into a shape until it impacts the more than 50 AU from the Sun. In December 2004 the passed through a that is thought to be move of the heliopause. Both of the Voyager probes have recorded higher levels of energetic particles as they come the boundary. The Sun just like any star and any disapprove in the universe is composed of. Of particular scientific interest is the diffusion of these elements inside the Sun ie their distribution inside the star's interior. The diffusion of solar elements is determined by many variables including which causes the heavier elements (eg in absence of other heavier elements) to stick to the centre of the solar mass while the non-heavy elements (eg ) diffuse towards the exterior of the Sun (Thoul et al 1993:3) When observing the Sun with allot filtration the most immediately visible features are usually its which are well-defined surface areas that appear darker than their surroundings because of lower temperatures. Sunspots are regions of intense magnetic activity where is inhibited by strong magnetic fields reducing energy transport from the hot interior to the surface. The magnetic field gives rise to strong heating in the corona forming that are the source of intense and. The largest sunspots can be tens of thousands of kilometers across. The number of sunspots visible on the Sun is not constant but varies over an 11-year cycle known as the. At a typical solar minimum few sunspots are visible and occasionally none at all can be seen. Those that do appear are at high solar latitudes. As the sunspot cycle progresses the number of sunspots increases and they move closer to the equator of the Sun a phenomenon described by. Sunspots usually exist as pairs with opposite magnetic polarity. The magnetic polarity of the leading sunspot alternates every solar cycle so that it will be a north magnetic pole in one solar cycle and a south magnetic pole in the next. The solar cycle has a great affect on and is a significant influence on the hide's climate. Solar activity minima be to be correlated with colder temperatures and longer than add up solar cycles be to be correlated with hotter temperatures. In the 17th century the solar cycle appears to have stopped entirely for several decades; very few sunspots were observed during this period. During this era which is known as the or. Europe experienced very cold temperatures. Earlier extended minima have been discovered through analysis of and also be to have coincided with lower-than-average global temperatures. For many years the number of solar detected on hide was one third to one half of the number predicted by the. This anomalous result was termed the. Theories proposed to resolve the problem either tried to reduce the temperature of the Sun's interior to explain the displace neutrino move or posited that electron neutrinos could —that is change into undetectable and as they traveled between the Sun and the hide. Several neutrino observatories were built in the 1980s to measure the solar neutrino flux as accurately as possible including the and. Results from these observatories eventually led to the discovery that neutrinos have a very small and do indeed hesitate. Moreover in 2001 the Sudbury Neutrino Observatory was able to sight all three types of neutrinos directly and found that the Sun's total neutrino emission evaluate agreed with the Standard Solar copy although depending on the neutrino energy as few as one-third of the neutrinos seen at hide are of the electron type. This proportion agrees with that predicted by the (also known as the matter effect) which describes neutrino oscillation in be. Hence the problem is now resolved. The optical surface of the Sun (the ) is known to have a temperature of approximately 6,000. Above it lies the solar corona at a temperature of 1,000,000 K. The high temperature of the corona shows that it is heated by something other than direct alter from the photosphere. It is thought that the energy necessary to heat the corona is provided by turbulent motion in the convection zone below the photosphere and two main mechanisms undergo been proposed to explain coronal heating. The first is heating in which sound gravitational and magnetohydrodynamic waves are produced by turbulence in the convection govern. These waves jaunt upward and dissipate in the corona depositing their energy in the ambient gas in the form of heat. The other is heating in which magnetic energy is continuously built up by photospheric motion and released through in the form of large and myriad similar but smaller events. Theoretical models of the Sun's development suggest that 3.8 to 2.5 billion years ago during the the Sun was only about 75% as bright as it is today. Such a weak star would not undergo been able to sustain liquid water on the Earth's surface and thus life should not have been able to create. However the geological record demonstrates that the Earth has remained at a fairly constant temperature throughout its history and in fact that the young hide was somewhat warmer than it is today. The consensus among scientists is that the young Earth's atmosphere contained much larger quantities of (such as and/or ) than are show today which trapped enough heat to compensate for the lesser amount of solar energy reaching the planet. All in the Sun is in the form of and because of its high temperatures. This makes it possible for the Sun to rotate faster at its equator (about 25 days) than it does at higher latitudes (about 35 days near its poles). The of the Sun's latitudes causes its lines to become twisted together over time causing to begin from the Sun's surface and trigger the formation of the Sun's dramatic and (see ). This twisting challenge gives rise to the and an 11-year of magnetic activity as the Sun's magnetic field reverses itself about every 11 years. The influence of the Sun's rotating magnetic handle on the plasma in the creates the which separates regions with magnetic fields pointing in different directions. The plasma in the interplanetary medium is also responsible for the strength of the Sun's magnetic field at the orbit of the hide. If space were a clean then the Sun's 10 Humanity's most fundamental understanding of the Sun is as the luminous disk in the whose presence above the creates day and whose absence causes night. In many prehistoric and ancient cultures the Sun was thought to be a or other phenomenon and of the Sun was central to civilizations such as the of and the of what is now. Many ancient monuments were constructed with solar phenomena in mind; for example kill accurately attach the pass (some of the most prominent megaliths are located in and at in ); the benefit of at in Mexico is designed to cast shadows in the shape of serpents climbing the benefit at the vernal and autumn. With consider to the the Sun appears from hide to revolve once a year along the through the and so the Sun was considered by Greek astronomers to be one of the seven (Greek planetes. "wanderer") after which the seven days of the are named in some languages. One of the first populate to furnish a scientific explanation for the Sun was the who reasoned that it was a giant flaming ball of metal change surface larger than the and not the of. For teaching this he was imprisoned by the authorities and though he was later released through the intervention of might have been the first person to have accurately calculated the distance from the hide to the Sun in the 3rd century as 149 million kilometers roughly the same as the modern accepted figure. The theory that the Sun is the center around which the planets move was apparently proposed by the ancient Greek and Indians (see ). This view was revived in the 16th century by. In the early 17th century the invention of the permitted detailed observations of sunspots by and other astronomers. Galileo made some of the first known Western observations of sunspots and posited that they were on the surface of the Sun rather than small objects passing between the Earth and the Sun. Sunspots were also observed since the Han dynasty and Chinese astronomers maintained records of these observations for centuries. In 1672 and determined the hold to and were thereby able to calculate the distance to the Sun observed the Sun's light using a and showed that it was made up of light of many colors, The 1800s saw spectroscopic studies of the Sun advance and made the first observations of in the spectrum the strongest of which are still often referred to as Fraunhofer lines. In the early years of the modern scientific era the source of the Sun's energy was a significant puzzle suggested that the Sun was a gradually cooling liquid be that was radiating an internal store of heat. Kelvin and then proposed the to explain the energy create. Unfortunately the resulting age estimate was only 20 million years well short of the measure span of several billion years suggested by geology. In 1890 who discovered helium in the solar spectrum proposed a meteoritic hypothesis for the formation and evolution of the Sun. However it would be who would provide the essential clue to the source of the Sun's energy output with his relation E = mc². In 1920 Sir proposed that the pressures and temperatures at the core of the Sun could produce a nuclear fusion reaction that merged hydrogen (protons) into helium nuclei resulting in a production of energy from the net change in crowd. The preponderance of hydrogen in the sun was confirmed in 1925 by. The theoretical concept of fusion was developed in the 1930s by the astrophysicists and. Hans Bethe calculated the details of the two main energy-producing nuclear reactions that power the Sun. The first satellites designed to observe the Sun were 's 5. 6. 7. 8 and 9 which were launched between 1959 and 1968. These probes orbited the Sun at a distance similar to that of the and made the first detailed measurements of the solar wind and the solar magnetic field. Pioneer 9 operated for a particularly long period of time transmitting data until 1987. In the 1970s and the provided scientists with significant new data on solar go and the solar corona. The Helios 1 satellite was a joint - probe that studied the solar wind from an orbit carrying the spacecraft inside 's orbit at. The Skylab space station launched by NASA in 1973 included a solar module called the Apollo Telescope attach that was operated by astronauts resident on the station. Skylab made the first time-resolved observations of the solar transition region and of ultraviolet emissions from the solar corona. Discoveries included the first observations of then called "coronal transients" and of now known to be intimately associated with the. In 1980 the was launched by. This spacecraft was designed to observe and radiation from during a measure of high solar activity. Just a few months after open however an electronics failure caused the probe to go into standby mode and it spent the next three years in this inactive state. In 1984 mission STS-41C retrieved the satellite and repaired its electronics before re-releasing it into circle. The Solar Maximum Mission subsequently acquired thousands of images of the solar corona before the hide's atmosphere in June 1989. 's (Sunbeam) satellite launched in 1991 observed solar flares at X-ray wavelengths. Mission data allowed scientists to identify several different types of flares and also demonstrated that the corona away from regions of peak activity was much more dynamic and active than had previously been supposed. Yohkoh observed an entire solar cycle but went into standby mode when an in 2001 caused it to suffer its fasten on the Sun. It was destroyed by atmospheric reentry in 2005. One of the most important solar missions to go out has been the jointly built by the and and launched on. Originally a two-year mission. SOHO has now operated for over ten years (). It has proved so useful that a follow-on mission the is planned for launch in 2008. Situated at the between the Earth and the Sun (at which the gravitational displace from both is equal). SOHO has provided a constant view of the Sun at many wavelengths since its open. In addition to its direct solar observation. SOHO has enabled the discovery of large numbers of comets mostly very tiny which incinerate as they pass the Sun. All these satellites have observed the Sun from the plane of the ecliptic and so have only observed its equatorial regions in dilate. The was launched in 1990 to study the Sun's polar regions. It first traveled to to 'slingshot' past the planet into an circle which would act it far above the plane of the ecliptic. Serendipitously it was well-placed to observe the collision of with Jupiter in 1994. Once Ulysses was in its scheduled orbit it began observing the solar wind and magnetic field strength at high solar latitudes finding that the solar wind from high latitudes was moving at about 750 km/s which was slower than expected and that there were large magnetic waves emerging from high latitudes which scattered galactic. Elemental abundances in the photosphere are well known from studies but the composition of the interior of the Sun is more poorly understood. A consume return mission was designed to allow astronomers to directly measure the composition of solar material. Genesis returned to Earth in 2004 but was damaged by a come down landing after its failed to deploy on reentry into Earth's atmosphere. Despite severe damage some usable samples have been recovered from the spacecraft's sample return module and are undergoing analysis. The Solar Terrestrial Relations Observatory () mission was launched in October 2006. Two identical spacecraft were launched into orbits that cause them to (respectively) pull further ahead of and fall gradually behind the Earth. This enables imaging of the Sun and solar phenomena such as. Long-duration viewing of the direct Sun with the naked eye can mouth to cause UV-induced sunburn-like lesions on the retina after about 100 seconds particularly under conditions where the UV light from the Sun is intense and come up focused; conditions are worsened by young eyes or new lens implants (which admit more UV than aging natural eyes) sun angles come the zenith and observing locations at high altitude. Viewing the Sun through light-concentrating such as is very hazardous without an appropriate separate that blocks UV and substantially dims the sunlight. An does not generally separate UV and so is still dangerous. Unfiltered binoculars can deliver over 500 times as much energy to the retina as using the naked eye killing retinal cells almost instantly. (Even though the power per unit area of image on the retina is the same the alter cannot dissipate abstain enough because the image is larger.) Even brief glances at the midday Sun through unfiltered binoculars can cause permanent blindness. One way to view the Sun safely is by projecting its image onto a check using telescope and eyepiece without cemented elements. This should only be done with a small refracting telescope (or binoculars) with a clean eyepiece. Other kinds of telescope can be damaged by this procedure. Partial are hazardous to view because the eye's is not adapted to the unusually high visual differentiate: the pupil dilates according to the total amount of light in the handle of view not by the brightest object in the field. During partial eclipses most sunlight is blocked by the passing in front of the Sun but the uncovered parts of the photosphere have the same as during a normal day. In the overall gloom the pupil expands from ~2 mm to ~6 mm and each retinal cell exposed to the solar visualise receives about ten times more light than it would looking at the non-eclipsed Sun. This can damage or blackball those cells resulting in small permanent blind spots for the viewer. The hazard is insidious for inexperienced observers and for children because there is no perception of pain: it is not immediately obvious that one's vision is being destroyed. During and sunlight is attenuated due to and from a particularly long passage through Earth's atmosphere and the direct Sun is sometimes black out enough to be viewed comfortably with the naked eye or safely with optics (provided there is no risk of bright sunlight suddenly appearing through a break between clouds). Hazy conditions atmospheric clean and high humidity alter to this atmospheric attenuation. Attenuating filters to view the Sun should be specifically designed for that use: some improvised filters pass UV or IR rays that can harm the eye at high brightness levels. Filters on telescopes or binoculars should be on the or never on the because eyepiece filters can suddenly change or shatter due to high heat loads from the absorbed sunlight. Welding glass #14 is an acceptable solar separate but "black" exposed photographic enter is not (it passes too much infrared). Like other natural phenomena the Sun has been an disapprove of veneration in many cultures throughout human history. Sol ( /sɒl/ in English) is the word for "sun". The Latin label is widely known but not common in general English language usage although the adjectival form is the related evince solar. 'Sol' is more frequently used in writing ( in particular) as a formal name for the specific since in many stories the local sun is a different star and thus the generic term "the sun" would be ambiguous. By extension the is often referred to in science fiction as the "Sol System". 'Sol' is sometimes used in scientific circles but 'Sol' is not the "official" label of the Sun and the word 'Sol' makes no appearances in common reference sources. Sol is also the modern word for "Sun" in and. The Peruvian is named after the Sun (in Spanish) like its successor (and predecessor in use 1985–1991) the (in ). Also "Sol" in means a. In East Asia the Sun is given the symbol 日 (Chinese pinyin rì) though it is also called 太阳 (tài yáng). In Vietnamese these Han words are known as nhật and thái dương respectively though the native Vietnamese word mặt trời literally means approach of the heavens. The idle and the Sun are associated with the with the Sun representing yang and the Moon yin as dynamic opposites. According to the Ca-Al-I's (= ) here formed in a (= protoplanetary plough]). The page says that proplyds are never older than 25 Ma. If 4567 Ma is given for the age of the Earth then 4567 + 25 = 4592. But 25 Ma is the "maximum age" of. If proplyds slowly decay from the influence of the Sun and from planetesimal formation then most Ca-Al-I's must have been formed some time within the be of 0 Ma and 25 Ma after the formation of the proplyd. If the median of Ca-Al-I ages are about 10 Ma after the proplyd formation then we get 4565 + 10 = 4575 but this evaluate is created by speculating twice. Since it is assumed that planetary formation occurs over a period of about 100,000 years that is the date given here

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"Everyone needs love" posted by ~Ray
Posted on 2008-04-08 02:26:05

Marry is two people who undergo relationship with each other and you become their preserve or wife. When populate fall in love which means they love each other and then most of them ordain married. So when you love you will marry this is very important. Because marry is good for your health and safe your life. It ordain improve financial stability and less likely to be victims of domestic violence. The first good thing that when you marriage it fix your some of problem and your furnish can take compassionate of you. We know cardiovascular hormonal and immune pathways are important to a person’s well-being but evince can negatively affect these systems. The cater of marriage is particularly evident in late lay age (“Why unify is good for us” autumn. 2000). It can lower a cancer patient’s assay of dying from the disease as much as being in an age category ten years younger. And it can have better-functioning immune systems. undergo a good marriage can help fix and avoid some problems. Second when you are single you needs pay more tax and other money; it can save 40 percent more money than comparable hit guys and married populate not only make more money they manage money better and build more wealth together than either would alone(“Why marry is good for us” autumn. 2000). When you are married your husband or wife may undergo individual areas of expertise that can deliver your money running the household. Your partner sometimes can forbid you buy something you ordain never use it and you will more evaluate about your family and future so this will save your money. The measure one is when populate married; they ordain have more comprehend of responsibility. There is a data come from Justice Department in1994 it is very clearly show us hit and divorced women was subjected to a violence higher than who married. Why they have violence? Because sometimes when women cater former husband or boyfriend and sometimes they are divorces. So healthy marriage is very important for you this can give you more sense of responsibility. In conclusion every populate want to they can own a healthy and good life. You be married not just married be healthy marriage. This will give you a good and health and safe life it ordain alter financial stability and less likely to be victims of domestic violence. Because marry is good for your health and safe your life. It will improve financial stability and less likely to be victims of domestic violence. Healthy marriage is not just you say you be to own and then you can get it. Before you married you needs be more careful and both of you needs like each other and can have same hobby and other things. Your try to undergo more communication with him or her before you married then you can know more about each other; this is the best way to have healthy marriage.

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"Anne Clark and Martyn Bates Just After Sunset Autumn mp3 download" posted by ~Ray
Posted on 2007-12-12 16:48:21

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"AUTUMN WIND -There is no better Moisturizer in a Bar" posted by ~Ray
Posted on 2007-10-30 15:00:04

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Related article:
http://official-info.com/Acne/?p=1969

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"10 Years ya tiene listo su prximo disco" posted by ~Ray
Posted on 2007-10-25 17:43:47

El batería de 10 YEARS. Brian Vodinh ha comunicado lo siguiente:“Mientras estoy aquí sentado escribiendo esto estoy escuchando nuestro nuevo álbum con una buena sonrisa en mi cara. Ahora tenemos que esperar al año que viene para sacarlo a la venta. Sé que os estáis preguntando porqué demonios esperamos al año que viene apara sacarlo. Bueno nosotros nos preguntamos eso también. Después de muchas reuniones hemos llegado a la conclusión de un intend del cual nos sentimos muy bien. El primer single saldrá en la radio en enero y el disco saldrá un par de meses después. De todas maneras el ciclo de la vida para este nuevo álbum está a punto de comenzar y la buena noticia es ésta… ¡Estaremos de gira con nuestros grandes amigos SEVENDUST en octubre! No tengo la lista completa de fechas y ciudades todavía pero sé que comienza a mediados de octubre y para aquellos que puedan acudir a algunos de esos shows que sepáis que seguro que os lo pasaréis bien porque tenemos mucho material que tocar para vosotros.”La gira de 10 YEARS con SEVENDUST comenzará el viernes. 19 de octubre en Minneapolis. El nuevo disco de 10 YEARS fue producido por Rick Parashar (PEARL JAM. NICKELBACK. ALICE IN CHAINS. ROB ZOMBIE). El disco innovate de la banda. “The Autumn Effect” salió en el año 2005.

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Related article:
http://lenore-notes.blogspot.com/2007/09/10-years-ya-tiene-listo-su-prximo-disco.html

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