View source for Talk:Sun/German translation

This is a translation of the German [http://de.wikipedia.org/wiki/Sonne article on the Sun]

The '''sun''' is a [[star]] in the center of our [[Solar system]] (the central star). In popular usage "sun" can also mean any [[star]]. The sun has a central meaning for life on [[Earth]]. With the exception of 
[[volcanism]] and [[tides]] all energetic processes on Earth, such as [[climate]] and [[biology|lives]], are propelled by [[solar energy|the solar energy of the sun]].

[[Image:Sun_SOHO_image.jpg|300px|thumb|The sun. Admission of the space probe [[SOHO]] in the light of ionized [[calcium]]. At the edge prominences are visible. The bright areas on the sun are called flares]]

== general ==

[[Image:SunLayers.png|400px|thumb|Structure of the sun]]

The '''sun''' is the by far largest [[heavenly body]] in the our solar system. Its diameter is approx. 109 times the diameter of the earth, and it unites 99.8 % of the total mass of the system on itself. The sun is a star from the [[main sequence]], its [[stellar classification|spectral type]] is G2, and it has [[luminosity class]] V. This means that the sun is a relatively normal, yellow star. Its mass amounts to for instance the double of the estimated [[average value]] of the stars in [[the Milky Way]]. Their mass builds itself to 75% up out [[hydrogen]] and to 25 % out [[helium]]. Regarding the number [[atom]]s amount to these portions of 92.1% and 7.8%. The sun carries out a circulation to [[equator]] in 25.4 days, in the environment of the poles lasts it 36 days. This difference in the scan time is called [[differential rotation]].

== structure ==

The sun consists of different zones with dish-shaped structure.

=== core ===

All energy produced in one as "core" designated zone the inside one the sun. The core extends from the center to approximately a quarter of the radius of the visible sun surface. Although the core constitutes only 1.6% of the sun volume, here approximately 50% of the solar mass are concentrated. At a temperature of approximately 15.6 million [[Kelvin|K]] the subject is in form one [[Plasma (physics)|Plasma]]s forwards. By [[proton proton reaction]] hydrogen cores merge into helium cores, whereby [[gamma radiation]] and [[neutrino|elektron neutrinos]] are produced. The produced helium cores have a slightly smaller mass than the original hydrogen cores. The mass difference is converted in accordance with the formula [[Relativitatstheorie|''E=mc<sup>2</sup>'']] into energy. In the core of the sun 700 million tons become hydrogen 695 million tons helium [[Kernfusion|fusioniert]] per second, whereby a total output of approx.. 4.·.10 26 = 400 quadrillionen Watts is set free. Actually the solar core is too "cold" for a nuclear fusion. The kinetic energy of the particles is not sufficient computationally, in order to overcome with a collision the strong repulsive forces of the positively charged protons (hydrogen cores). The fact that fusion take place nevertheless to lead is on [[Quantum mechanics|quantum mechanical]] [[tunnel effect]] back. In accordance with quantum mechanics a proton behaves like a spread wave without exactly defined place, its energy varies around an average value. There is a very small probability that two protons approach so far that a fusion takes place. The energy level of the repulsive forces "is tunnelled through" thereby as it were. Thus the probability of a fusion of two hydrogen cores is very small the inside one the sun. Since however an immense number of cores is present, nevertheless enormous energy quantities can be set free. The "braked" nuclear fusion has the crucial advantage for the solar system and the life on earth that the sun deals economically with its energy reserves and radiates during a long period constant energy quantities.tibo






=== radiation zone ===

Around the core the "radiation zone in such a way specified" lies, which constitutes about 70 % of the sun radius. In [[vacuum]] the universe move Gamma [[photons]] with [[speed of light]] by the area. In the inside such a high density that the photons collide again and again with the particles of the plasma, to the sun [[Absorption|absorbed]] and again to be radiated. They move on a complete coincidental course and
[[Diffusion|diffuse]] thereby direction sun surface. Statistically a photon needs about 170,000 years, in order to pass the radiation zone. This means that the light, which we receive today from the sun was already produced before according to long time. With each collision in the radiation zone the radiation energy of the photon decreases and its [[wavelength]] increases. The gamma radiation is converted into [[x-ray]]. Differently than the photons the neutrinos arrive almost unhindered by the layers of the sun, since they hardly step with subject into reciprocal effect. The neutrinos reach, since they move with speed of light, already after eight minutes the earth, whereby they cross the planet nearly unhindered. In each second about 70 billion neutrinos crosses a square centimeter of the earth's surface.
kivin clint pinkian author

=== convection zone ===

The radiation zone the "convection zone" follows. At the frontier to the radiation zone the temperature amounts to still approx.. 2 millions Kelvin. The energy is delivered in this zone no more by radiation, but continued to transport by a current ([[convection]]) that of plasma outward. Hot subject in enormous rivers rises outward, cools down there and sinks again in the sun inside down there. Since the plasma freshly ascended is hotter and thus brighter than the descending thing, are recognizable [[convection cell]]s with one [[telescope]] as [[granulation]] the sun surface.

=== surface and environment ===

Above the convection zone one is appropriate for only about 400 km thick layer, [[photosphere]]. The temperature amounts to here approx.. 6,000 K (5,700 °C). Here the energy is delivered again in the form of radiation. Only in the photosphere, the energy of the photons decreased so far that they are visible for the human eye. The photosphere is thus a ball from light, which represents the sun surface visible for us. Generally the photosphere is regarded as the actual surface of the sun, although the sun does not possess a sharp outside border. Over the photosphere extends the [[chromosphere]], which with one [[solar eclipse]] as reddish leuchterscheinung to see is. The temperature increases here on over 10,000 K, while [[gas density]] by the factor 10 -4 to 10,-15 g/cm³ decreases.

[[image:Solar Corona.jpg|thumb|Die corona, taken up of SOHO]]

Over the chromosphaere lies the [[corona]], in which the density decreases again by the factor 10 -4 to 10,-19 g/cm³. The temperature in the corona can rise on up to two million Kelvin. The cause for the fact lies in the fact that by the sun apart from the radiation still additionally energy is registered by one either mechanical or magnetic heating mechanism, whose exact nature is still unclear into the corona. Because the density of the corona decreases outward faster, than the energy can be removed, it comes at the lower limit of the corona within less hundred elevator kilometers to a temperature rise around one million degree, to at these high temperatures the additional heating energy than [[solar wind]] escaping can. The corona can become so hot thus only due to its extremely small density. With [[solar eclipse]]s visible expansion of the corona goes over several millions kilometer. It shows thereby a radial structure and changes with the cycle [[sunspot]]s. In the maximum the jets run after all sides, in the minimum run them strongly shortened to Poland.

== magnetic field ==

The sun possesses extraordinarily strong [[Magnetic field]]s, which by the current [[electric|electrically]] conducting gases to be caused. The conductivity of the plasma in the sun inside corresponds to [[copper]] at room temperature. In the sun electric currents in an order of magnitude of circulate to 10<sup>12</sup> [[ampere]]. The inside of the sun works thus as a gigantic [[direct current]] generator, which the kinetic energy of an electrical conductor converts into electricity and a magnetic field. One assumes at present this direct current generator effect is effective only in a thin layer at the soil of the convection zone.

[[Image:Sonnen fleck.jpg|thumb|Eine expanded group of sunspots; between them the granulation is visible. The group of marks has a Laengsausdehung of approximately 100,000 km (to the comparison: The earth has a diameter of approx.. 12,700 km)]]

Visible effects of the magnetic fields are [[sunspot]]s and [[Solar prominence|prominence]]s. Sunspots are relatively cool ranges of the sun atmosphere. Their temperature is appropriate for investigations between 3.700 and 4.500 K. through [[spectroscopy|spectroscopy] could be stated that within the range of the sunspots strong magnetic fields prevail. [[spectral line]]s of elements, which normally are with a wavelength, appear three-divided with presence of a magnetic field ([[Zeeman effect]]), whereby the distance of the lines strengthens proportionally to the field is. The magnetizing force in the surrounding field of the sunspots can amount to up to 3,000 [[Gauss]] and is thus a thousand times stronger than the terrestrial magnetic field at the earth's surface. In the sun the magnetic fields cause an inhibition of the convection currents, so that less energy outward one transports. The darkest and coolest zones on the sun are thus the places with the strongest magnetic fields. Sunspots arise in groups, whereby mostly two remarkable marks dominate, the one against set magnetic adjustment exhibit (a mark is as it were "a magnetic north pole", which others a "South Pole"). Such bipolar marks are usually in east west direction, parallel to the sun equator, aligned.

[[image:Magnetfeld.jpg|thumb|Modell of the magnetfeldlinien between the sunspots]]

Between the marks magnetic field lines are formed in the form of loops. Along these lines ionized gas is noted that becomes visible in the form of prominences or filaments (prominences are features at the edge, filaments on the "sun disk"). The total number of the sunspots is subject to a cycle of approximately eleven years. During a mark minimum hardly sunspots are visible. With the time are formed increasingly marks in a range from 30° northern and southern latitude. These active mark belts move increasingly toward equator. After approximately 5.5 years the maximum is reached and the number marks removes slowly again. After a cycle the global magnetic field of the sun commutated itself. Before the magnetic north pole is now the magnetic South Pole. The exact causes for the eleven-year old cycle are not yet completely investigated. At present one proceeds from the following model: At the beginning of a cycle, in the minimum, the global magnetic field of the sun is bipolar aligned. The magnetfeldlinien run straight-lined over the equator from pole to pole by the differenzielle rotation are shifted against each other the electrically charged gas layers, whereby the magnetic fields are increasingly tossed, rotated and twisted. The magnetic field lines stand out increasing from the visible surface and cause the formation of marks and prominences. After the mark maximum the magnetic field aligns itself again again.

== Oscillations ==

The entire sun [[oscillation|oscillates]] at different [[frequencies]]. It rings as if it were as an enormous bell. However we can not "hear" the [[acoustic wave]]s on earth, since they do not travel through the vacuum of space. With special methods, one can make the oscillations visible, however. Oscillations from the sun's interior move the photosphere in and out. Due to [[Doppler effect]]s  the absorption lines of the solar spectrum are shifted, depending upon direction of motion of the photospheric gases. The prevailing oscillation has a frequency of approximately five minutes (293 seconds, +/- 3 seconds). Within the convection zone violent [[turbulence]] prevails, whereby ascending convection cells produce acoustic waves by the motion of the surrounding gases. Outward moving acoustic waves reach the boundary layer of the photosphere. Since the density decreases rapidly there, the waves do not continue outward, but rather are reflected back into the sun's interior. With increasing depth, the density increases as does the [[speed of sound]], so that the wave front is curved until it is again moving outward. Acoustic waves can be strengthened by this repeated reflection and constructive interference, creating [[resonances]]. The convection zone works thus as an enormous [[resonant body]], transferring the oscillation to the overlying photosphere. The evaluation of the oscillations allows statements about the internal structure of the sun. Thus the expansion of the convection zone can be determined. Similar to the research of [[seismic]] waves on earth, one deals with the solar science of [[Helioseismology]].

== reciprocal effect of the sun with its environment ==

the sun affects also the interplanetary area with their magnetic field and particularly with the particle emission, [[solar wind]]. This particle stream can leave the sun with several 100 km/s and displaces [[interstellar Material|Interstellar medium]] up to a distance of more than 10 billion kilometers. With flare outbreaks both speed and density of the solar wind can increase strongly and on earth beside [[Aurora (astronomy)|Northern Lights]] also disturbances in electronic systems and in radio traffic to cause.

== Solar data ==

{| border="1" style="border-size:1px;border-color=#DDDDDD" cellspacing="0" cellpadding="2"
! &nbsp;
! Sun
! Relationship sun/earth
|-
| star class (see [[spectral class]] and [[luminosity class(??)]])
| style="text-align:center" | G2V
| style="text-align:center" | -
|-
| time up to the end of the hydrogen burning in the center
| style="text-align:center" | about 4.5?5 Million year
| style="text-align:center" | -
|-
| average [[diameter]]
| style="text-align:center" | 1,392,000&nbsp;km
| style="text-align:center" | 109.25
|-
| [[Schwarzschild radius]]
| style="text-align:center" | 2.95325 km
| style="text-align:center" | 332,724.365
|-
| average [[apparent diameter]]
| style="text-align:center" | 31'59.3"
| style="text-align:center" | -
|- 
| solar gravitation constant (''G''·''M'')
| style="text-align:center" | 1.32712440018·10<sup>20</sup>&nbsp;N m<sup>2</sup> kg m<sup>-1</sup>
| style="text-align:center" | 332,946
|-
| [[Mass]] 
| style="text-align:center" | 1.9884·10<sup>30</sup>&nbsp;kg
| style="text-align:center" | 332,946
|-
| mass loss per second by radiation
| style="text-align:center" | 4.28·10<sup>9</sup>&nbsp;kg
| style="text-align:center" | -
|-
| mass loss per second by solar wind 
| style="text-align:center" | ca, 1·10<sup>9</sup>&nbsp;kg
| style="text-align:center" | -
|-
| mass loss until today by radiation 
| style="text-align:center" | ca, 520·10<sup>24</sup>&nbsp;kg = 87 earth masses
| style="text-align:center" | -
|-
| escape velocity 
| style="text-align:center" | 617.319 km/s
| style="text-align:center" | 62.927
|-
| [[density]] 
| style="text-align:center" | 1,408 g/cm³
| style="text-align:center" | 0.2553
|-
| density (center) 
| style="text-align:center" | 150&nbsp;g/cm³
| style="text-align:center" | 11.1 <!-- earth: 13,5 g/cm^3 -->
|-
| [[pressure]] (center) 
| style="text-align:center" | >&nbsp;2·10<sup>16</sup>&nbsp;[[Pascal (Einheit)|Pa]]
| style="text-align:center" | -
|-
| surface acceleration 
| style="text-align:center" | 273,96 m/s²
| style="text-align:center" | 27.9
|-
| average [[apparent brightness]]
| style="text-align:center" |-26<sup>m</sup>.8
| style="text-align:center" | -
|-
| [[absolute brightness]] 
| style="text-align:center" | 4.8<sup>M</sup>
| style="text-align:center" | -
|-
| [[temperature]] (center) 
| style="text-align:center" | 15·10<sup>6</sup>&nbsp;[[Celsius|C°]]
| style="text-align:center" | 2,150 <!-- earth: 7.000 K -->
|-
| temperature ([[photosphere]]) 
| style="text-align:center" | ca. 6,100 °C
| style="text-align:center" | -
|-
| temperature ([[corona]]) 
| style="text-align:center" | ca. 1?2 Million deg K
| style="text-align:center" | -
|-
| [[black body|Effective temperature]] 
| style="text-align:center" | 5,778 K
| style="text-align:center" | -
|-
| radiation maximum 
| style="text-align:center" | ca. 500 nm (green Light)
| style="text-align:center" | -
|-
| [[luminosity]]
| style="text-align:center" | 3,846·10<sup>26</sup>&nbsp;[[Watt (Einheit)|W]]
| style="text-align:center" | -
|-
| [[Intensity|Specific radiant emittance]] (surface) 
| style="text-align:center" | 6.318·10<sup>7</sup>&nbsp;W/m<sup>2</sup>
| style="text-align:center" | -
|-
| [[Rotation|Rotation period]] at [[equator]] 
| style="text-align:center" | 25 d 9 h 7 m
| style="text-align:center" | 25,38
|-
| [[rotation speed]]  at [[equator]] 
| style="text-align:center" | 1856.847 m/s
| style="text-align:center" | 4,01
|-
| [[Rotation|Rotation period]] at 75° Breite
| style="text-align:center" | 31 d 19 h 12 m
| style="text-align:center" | -
|-
| inclination of the axis against the ecliptic
| style="text-align:center" | 7°15'
| style="text-align:center" | -
|-
| [[distance]] to the center [[galaxy]]
| style="text-align:center" | 25,000 bis 28,000 light years
| style="text-align:center" | -
|-
| scan time around the center of the galaxy
| style="text-align:center" | ca. 225,000,000 years
| style="text-align:center" | -
|-
| [[peripheral speed]] around the center of the galaxy
| style="text-align:center" | ca. 220 km/s
| style="text-align:center" | -
|}

== study of the sun ==

As the most important heavenly body for terrestrial [[life]] the sun already enjoys before [[historiography]] the attentive observation of [[Man]]. [[Kultstaette]]n as [[Stonehenge]] were established, in order to determine the position and the run of the sun, in particular [[solstice]]s. It assumed that some still older places are likewise used for the sun observation, secured is this however not. The process of the sun as well as sun darkness are particularly observed, very attentively, documented by the different cultures. In recordings from the old [[China]] observations of particularly violent sunspot activity were already occupied. The development of the [[telescope]] led to the discovery of sunspots in the year [[1610]] by [[Galileo Galilei]]. [[Johann Fabricius (Astronom)|Johann Fabricius]] marks [[1611]] independently of Galilei and described it discovered for the first time in a scientific paper. Marks on the sun disk it attributed the observed migration applicable to the self-rotation of the sun. [[1619]] postulated [[Johannes Kepler]] a solar wind, there the tail of [[comet]]s is turned away from the sun always. [[image:solar spectrum.jpg|thumb|Das complete spectrum of the sun in the visible light with the absorption lines. In this picture the entire spectrum, which is actually a completely long thin volume, was divided into several strips and arranged among themselves. For the first time dark "marks" are the spectral lines of of the particulars wavelength coverages]] [[1802]] pointed [[William Hyde Wollaston]] to dark lines ([[Absorptionslinie]]n) in the solar spectrum after. [[Joseph of Fraunhofer]] the lines off [[1814]] systematically, it examined therefore also as "Fraunhofer lines" is bezeichent. [[1843]] discovered [[Samuel Heinrich Schwabe]] the cycle of the sunspot activity. [[1849]] [[Relativzahl|sunspotenrelativzahl]] one introduced, which shows the number and size of sunspots. Since that time marks are regularly observed and counted. [[1889]] developed [[George resound]] [[spectroheliograph]]en. [[Henry Rowland]] completed [[1897]] an Atlas of the solar spectrum, that contains all spectral lines. [[1908]] discovered George resounds the fragmentation of spectral lines within the range of the sunspots by magnetic forces (Zeeman effect). [[1930]] [[Berne pool of broadcasting corporations Ferdinand Lyot]] the solar corona observed outside of a total darkness. For a long time however it was unclear, from where the sun receives its energy. So one had the impression that the sun was a glowing, burning body. However the fuel would have been enough for only a few thousand years. William Thomson, the later [[lord Kelvin]], assumed the sun shrinks by the force of its own gravity and converted the kinetic energy of the suns particles into warmth. So could deliver the sun for approximately hundred million energy. With the discovery of terrestrial [[radioactivity]] one stated however that the rocks of the earth's crust must be several billion years old. Only the decoding of the atomic procedures brought a solution. [[Ernest Rutherford]] described a connection between radioactivity and nuclear transformation. [[Arthur Stanley Eddington]] concluded that inside a star elements are converted to merge and into others, whereby energy is set free. Since when spectroscopic investigation mainly hydrogen was determined, one assumed this element played a crucial role.In [[1938]] [[Hans Bethe]] finally described the processes [[proton proton reaction]] , which run off the inside one the sun. [[1942]] it was stated that the sun [[Radiowelle]]n radiates. [[1949]] [[Herbert Friedman]] the solar [[x-ray]] proved. In the course of the time special [[solar telescope|solar observatories]] were established, which serve the sun excluding the observation. [[1960]] the oscillation of the photosphere became nachgewisen. This was the Begin [[Helioseismologie]], which [[Eigen oscillation]]s of the sun examines and from this the internal structure as well as processes derives. The measurement sun [[Neutrino]]s enormous underground [[Detektor]]en became established. [[image:Sun_in_X-Ray.png|thumb|Die sun in the Roentgen light. Admission of Skylab]] a set of [[satellite]]s was sent for the observation of the sun into an earth orbit. By means of the satellites in particular wavelength coverages can be examined ([[ultraviolet]], x-ray), which otherwise of [[terrestrial atmosphere]] to be absorbed. [[1973]] the started [[space station]] [[Skylab]] among other things a Roentgen telescope had on board. [[1990]] the started [[space probe]] [[Ulysses]] it flew over so far twice the poles of the sun, whereby the probe each time with the giant planet [[Jupiter (planet)|Jupiter]] by means of [[Swing By]] maneuver "momentum" to get had. In [[1995]] the probe [[SOHO]] was launched toward the sun. SOHO is now in [[point of lying rank]] the L1 and observes the sun with twelve different instruments.

== visible features and observation of the sun ==

With [[Telescope]]s one knows the activities of the sun in the form of [[Prominence]]s and [[sunspot]]s to make visible. Likewise to observe there violent outbreaks are, so mentioned [[flare]]s, which is recognizable as brighter and thus hotter areas already with small instruments. '''caution, a direct observation of the sun with or without telescope is dangerous for the eyes!''' Only during the total phase of a total solar eclipse can be done without the protection, since the brightness of the corona and the prominences is weaker around several orders of magnitude than those the photosphere (and thus by a sun filter also hardly recognizably).

[[image:Sun projection with spotting scope large.jpg|thumb|240px|solar beobachtung with a spectiv according to the projection method]]

[[Sun observation]] happens most simply, as the eyepiece picture of a telescope or binoculars on a white surface canvas (e.g. a canvas or a piece of pasteboard) is projected. [[optical Abimageung|Abimageung]] the sun can be regarded safely. One calls this procedure [[eyepiece projection]]. Is likewise possible an observation by special [[solar filter]]s, these are foils or coated glasses, which before [[eye]] to be held or before [[objective (Optik)|Objektiv]] be attached. In addition a detailed observation is possible with one [[Herschelprisma]]. With all described modes of observation the entire spectrum of the sunlight is absorbed, which sun observed in the "white light". Become visible sunspots, flares and the granulation. In order to observe prominences, it requires special construction units or telescopes. With one [[pro tube satchel beginning]] the sun is taken off by means of an occulter - an artificial total solar eclipse is produced as it were. The prominences ascending at the solar rand become by one sucked.'' h-alpha-filter'' observes. This is particularly more narrow-band [[interference filters]], which lets through only the low-red light of the ionized hydrogen. An observation for the entire sun surface in this spectral region make possible sucked.'' h-alpha-telescopes''. Thus prominences, filaments, marks and Flares can be observed. These telescopes became in the last years very low-priced and become of [[Amateurastronom]]en increasingly begun. The corona can only with a total solar eclipse or by means of special equipment, [[Coronagraph]]s, to be observed. With free eye the sun can be only regarded with hazy sky briefly after sunrise or briefly before sunset. [[terrestrial atmosphere]] swallows the largest part of the light, in particular also the UV radiation. However the atmosphere in horizon proximity reduces also strongly the illustration quality and causes a vertical upsetting of the sun picture as consequence [[Refraktion|Lichtbrechung]]. The fact that the going down sun in horizon proximity looks larger, however not, how often assumes, a consequence of the refraction at the air layers, but an optical deception, which of the perception psychology under the term [[Mondtaeuschung|Mondtaeuschung]] is is examined and explained.

== culture history ==

The sun is the central Gestirn in the sky, of it depends all life on earth. This paramount meaning was ago conscious to humans since age. Many earlier cultures admired it than divinity. The regular the daily and annual return of the sun was partly fearfully expected and by means of [[solar kult|kulti]] or [[Magie|magi]] [[Ritual]]e sworn to. Particularly the occurrence of one [[solar eclipse]] solved large confusion and fear out. In the old [[China]] one, a Drache believed the sun would devour. By the meeting of large noise one tried to induce the Untier to release the sun again. For [[Sumerer]] the sun embodied the sun God [[Utu]]. With [[Babylonier]]n corresponded it to the God [[Schamasch]], which entered each day the sky and whose jets nothing remained hidden. In the old [[Egypt]] became [[RA]] (also RH or Atum) as sun God admires. "Ketzer" [[Pharao]] [[Echnaton]] later only [[Aton]], the personifizierte sun disk permitted, than only God and created all other Egyptian Gods off. In [[Antique one]] [[Greece]] one admired the sun God [[Helios]], which drove with its sun car daily over the Firmament. To a large extent the unbesiegbare [[Rom|roemi]] God [[Sol invictus]] corresponded to it, whose cult was far common in the Kaiser era. From that Antique one taken over is the sun as symbol of the Vitalitaet in [[Astrologie]]. In [[Nordi Mythologie|nordi mythology]] the Gods formed the sun out of transmitting and put them into a car. The goddess [[Sol (Mythologie)|Sol]] drives the sky with the car over, pulled from the Roessern [[Alsvidr]] and [[Arwakr]]. The bottom plate becomes steady by the wolf [[Skalli]] (Skoll) pursues. On the day of the world fall ([[Ragnaroek]]) the wolf will devour the sun. In the early [[Mexico]] the sun God [[Tonatiuh]] was admired of [[Aztecs]]. With [[Maya]] and [[Inka]] were [[Itzamná]] and/or [[Inti]] the main divinities. The observation of the sun (and other stars) and the determination of their points of course ([[Aequinoktium|Tag ones and night-same]], summer and Winter[[solar wende]]) was a condition for the production of [[Kalender]]n. Thereby important seasonal events could be predetermined, like the arrival [[Nil]]hochwassers in old Egypt, the most favorable time of the seed or the arrival of the autumn towers dangerous for the navigation. Pre-Christian cult places, as [[Stonehenge]], had been established obviously for such observation purposes. The plant of Stonehenge is in such a way aligned that in the morning [[Mittsommer]]tages, if the sun their highest northern position comes up reached, the sun directly over a position stone ("heel stone") and the sunbeams in straight lines line the inside the building penetrates. [[bronzezeit]]liche [[sky disk of Nebra]] likewise an instrument seems to have been for sky observation. Their golden edges are interpreted among other things as "sun barks", a religious symbol of the bronzezeit. That antique conception of the world generally assumed the earth formed the center of the universe. Sun, moon and the planets moved on accurate circular paths around the earth. This conception, in summary of [[Ptolemaeus]], kept itself nearly 2,000 years long. In particular the church defended this conception of the world, particularly since also in [[Bible]] is stated that the sun moves. However the model weaknesses showed. So the movement of the planets could be explained only by complicated auxiliary constructions. Already [[Aristarch of Samos]] postulated in 2. Century v. Chr. that the sun represents the center of the world. The scholars [[Nikolaus of Kues]] and [[Regiomontanus]] took up this thought more than 1,500 years later again. [[Nikolaus Copernicus]] a mathematical basis for it tried to create in its work'' [[De Revolutionibus Orbium Coelestium]]'', which did not succeed to it finally. Its work energized however further research and prepared the foundation for the "Copernican conception of the world". Copernicus's ' work of the church first as heresy one did not regard, since it represented a purely mathematical model. In later years, than scholars went to converting Copernicus's ' conception into a material conception of the world the church turned however decided against such "umstuerzlerischen" thoughts. Scholarly one, as Galilei, which had likewise arrived at the realization of a central sun, became of [[Inquisition]] pursues. By further observations, accurate regulations of the planet courses, the introduction of the telescope and the discovery of the laws [[celestial mechanics]], interspersed itself [[Helicentric worldview|heliocentric conception of the world]] gradually. The further progress of the astronomy resulted in finally that also the sun does not take an outstanding position in the universe, but a star under but billions stars is.

== history of the development of the sun ==

The sun formed 4.6 billion years ago from the [[Gravitation|gravitational]] collapse of an [[interstellar Gas|interstellar gas cloud]]. This collapse, in whose process also the planets developed, and which following relaxation phase was after approximately 50 million years locked. Finally the following history of the development of the sun leads one [[red giant]] across its current condition to that and across an unstable final phase in the age by approximately 12.5 billion years to one [[white dwarf]], which from one [[planetary nebula]] is surrounded. This expiration can be modelled today on the basis the laws [[physics]] and to the knowledge [[Kernphysik|nuclear physics]] of the processes from laboratory experiments, quite exactly in [[computers]]. The characteristic data of the individual phases is indicated in the table <ref>Sackmann, 1993</ref>. The index zero marks the today's characteristic data of the sun, i.e. at the age of 4.6 billion years.

{| border=1 cellpadding=1 cellspacing=0 align=center
|- bgcolor="#dfdfdf"
!&nbsp;&nbsp;Phase&nbsp;&nbsp;
!Time in<br/>&nbsp;&nbsp;Million Y.&nbsp;&nbsp;
!&nbsp;&nbsp;Luminosity&nbsp;/&nbsp;L<sub>0</sub>&nbsp;&nbsp;
! &nbsp;&nbsp;Radius&nbsp;/&nbsp;R<sub>0</sub>&nbsp;&nbsp;
|- 
|align=center |Main sequence star
|align=center |11,000
|align=center |0.7–2.2
|align=center |0.9–1.6
|- 
|align=center |Transition phase
|align=center |700
|align=center |2.3
|align=center |1.6–2.3
|- 
|align=center |Red Giant
|align=center |600
|align=center |2.3–2,300
|align=center |2.3–166
|- 
|align=center |Begin helium burning
|align=center |110
|align=center |44
|align=center |ca. 10
|- 
|align=center |Helium layer burning
|align=center |20
|align=center |44–2,000
|align=center |10–130
|- 
|align=center |Unstable phase
|align=center |0.4
|align=center |500–5,000
|align=center |50–200
|- 
|align=center |&nbsp;&nbsp;Transition to White Dwarf&nbsp;&nbsp;<br>&nbsp;&nbsp;with Planetary nebula&nbsp;&nbsp;
|align=center |0.1
|align=center |3,500
|align=center |100–0.08
|- 
|}

=== Protostellar phase ===

Forwards approx.. 4.6 together billion years pulled an enormous gas and dust cloud under the own force of gravity. In the center of the cloud the subject was ever more closely together pressed, whereby pressure and temperature continued to rise always. At this time already large energy quantities were delivered in the form of radiation. This stage is called the [[Protostellar]] phase.

=== Main sequence star ===

The temperature and the pressure in the center rose so far, until the nuclear fusion processes began. Thus a radiation pressure became effective, which worked against the force of gravity. The further contraction was stopped, the star stabilized. The sun had the stage of a so-called [[Main sequence]] star reached. In this phase it stays 11 billion years. In this time [[luminosity]] around the three-way of 0,7 L<sub>0</sub> to 2,2 L<sub>0</sub> and the radius rises to nearly double from 0,9 R<sub>0</sub> to 1,6 R<sub>0</sub> on. At the age of 5.5 billion years, i.e. in 0.9 billion years from today on, the middle temperature on the earth's surface the critical parameter of 30, for higher organisms, exceeds °C <ref>Bounama, 2004</ref>. A further billion years later are reached 100 °C. At the latest at age of 9.4 billion years the hydrogen in the sun center triumphs, and the fusion zone shifts into a dish-shaped range around the center, which continues to move in the course of the time outward. This procedure does not lead however for the time being to a change of the outwardly visible sun parameters. In the period of 11 to 11.7 billion years a contraction phase of the burned out core zone made of helium begins. The sun radius on 2,3 R<sub>0</sub> increases. To remove the sun will more reddish and begins themselves from the main sequence in the so mentioned [[Hertzsprung Russell diagram]]. Up to this time the mass loss amounts to less by solar wind than parts per thousand.

=== red giant ===

In the period of 11,7 to 12.3 billion years a dramatically accelerated rise of luminosity and radius uses. By the increase of the surface the sun radiates still more reddish. In the final phase of this development the sun reaches a luminosity of 2.300 L<sub>0</sub> and a radius of 166 R<sub>0</sub>. That corresponds for instance to the radius of the orbit [[Venus (Planet)|Venus]]. Venus and [[merkur (Planet)|Mercury]] are destroyed. Seen from the earth the sun takes now a large part of the sky, and the earth's crust is melted to only one lava ocean. By the small gravitation at the sun surface the sun in this phase loses 28 % of its mass by solar wind. Toward end of this phase a portion of up to 1,3.10 -7 M<sub>0</sub> per year flows as interstellar gas into space, whereby M<sub>0</sub> designates the mass of the today's sun. By the smaller solar mass also the attraction sinks on the planets, so that their course radii increase by in each case 38%. Since the core zone of the sun produces no more energy, it continues to give way to the gravitation and contracted, until finally [[density]] approximately to the 10.000 times of the today's value rose.

=== helium flash and burn phase ===

By the contraction of the central region there the temperature rises finally to 10 8 K. At this value the fusion turns from helium to carbon. Due to the extreme density of the order 10 6 g/cm 3 in the center and thereby the connected [[Neutrino]] cooling, ignites the fusion reaction first within a hotter spherical zone around the center. Usually the energy freed thereby would lead to an expansion of the core, which stabilizes the temperature. The core zone is however in a special [[quantum mechanical|quantum mechanical]] [[degenerate]] state, which has as a consequence, which is invested the energy first into the dissolution of the degeneration. Therefore first no stable condition is possible, so that the helium fusion uses in form of a gigantic explosion, which is known as the [[helium flash]]. The sun achievement rises to 10 10 L<sub>0</sub> for several seconds. That corresponds to about 10 % of the luminosity of the entire Milky Way. Only after a conversion of 3 % of the helium reservoir an expansion begins and stops this power excursion. This explosion takes place only in the central site and is not not noticeable outwardly first. It pushes however the hydrogen fusion zone further outward, their temperature therefore decreases and concomitantly the transformation of energy. Paradoxically thereby luminosity sinks starting from around nearly a factor 100 as outward consequence of helium flash within the next 10,000 years. Follows a phase of 1 million year, in which the sun parameters reciprocate to itself a stable condition of the helium fusion in the center adjust, which afterwards 110 million years stops. At the same time also the dish-shaped hydrogen fusion zone burns further further outside. In this time luminosity remains almost constant with 44 L<sub>0</sub> and the radius with 10 R<sub>0</sub>.

=== helium layer burning ===

Afterwards also the helium is in the sun center used up and it begins a phase of the helium layer burning, which persists 20 million years. Thus now two into one another geschachtelte dish-shaped fusion zones exist. In the center carbon collects itself and contracts gravitationally. Thus a renewed enormous rise of luminosity of 2.000 L<sub>0</sub> and an increase of the radius of 130 R<sub>0</sub>is connected. Toward end the sun loses thereby proportion of 0,1 M<sub>0</sub>. In the last 500,000 years of this phase one expects further unstable situations in connection with the reciprocal effect between the contracting core and the helium fusion zone, with which brief power excursions can occur by helium fusion with approximately 10 6 L<sub>0</sub>. A probable scenario would be for example four of such helium flashes in the distance of approximately 100,000 years. As consequence of each of these helium flashes and the associated expansion of the hydrogen layer the fusion can be stopped in the following 200 years temporarily completely there. The outward consequence of helium flash would be therefore again first a reduction of luminosity. After 400 years the energy of helium flash reaches the surface. Luminosity and radius rise on and [[Relaxation|relaxieren]] in the following 10,000 years again. Variations of luminosity between 500 L<sub>0</sub> and 5,000 L<sub>0</sub> are expected as well as radius variations between 50 R<sub>0</sub> and 200 R<sub>0</sub>. In the phases of maximum expansion the sun surface is enough to to the today's Earth's orbit near. Only by the increase of the Earth's orbit diameter the earth of the complete destruction escapes. At the same time the sun in these phases repels altogether a mass from further 0.05 M<sub>0</sub>.

=== white dwarf and planetary nebula ===

By the mentioned mass losses the sun loses the entire outside covering including the hydrogen and helium fusion zone. About 100,000 years after last helium flash therefore the hot internal core is opened, which essentially consists of highly compressed carbon and oxygen. Its radius amounts to only 0.08 R<sub>0</sub>, for it however its surface temperature 120,000 K. its luminosity amounts to initially 3,500 L<sub>0</sub>. Due to the high temperature this radiation contains an enormous portion of [[ultraviolet radiation]], which energizes the repelled gas cloud of the sun now for shining. Since the speed of the solar wind constantly increases, the gases discharged in former times are caught up by the later and often compressed to a spherical gas shell. For an observer standing outside the bright gases in this case appear as ring, which as [[planetary nebula]] are designated. By evaporating the gas this feature expires after some 10,000 years again, and in the center remains the radiating remainder of the sun, which one calls white dwarf. It has only about the size of the earth, but a mass of 0,55 M<sub>0</sub>. Its density amounts to therefore about a ton per cubic centimeter. It does not possess an internal energy source, so that its radiation leads to a calorific loss. After a comparatively rapid cooling in the initial stage by extreme luminosity the surface temperature sinks on values, at which a radiation is years possible due to clearly lower luminosity over several dozen of billions, before the sun than [[black dwarf]] in the optical [[spectrum|spectral range]] completely expires.

== see also ==

* [[astronomy]], [[cosmology]], [[polar light]] * [[sun research]] * [[solar system]]

== References ==

* Kenneth R. Lang: ''Die Sonne - Stern unserer Erde'', Springer- Verlag Berlin, Heidelberg, New York, 1996, ISBN 3-540-59437
* Rudolf Kippenhahn: ''Der Stern von dem wir leben'', DVA, 1990, {{ISBN|3-421-02755-2}}
* Helmut Scheffler, [[Hans Elsässer]]: ''Physik der Sterne und der Sonne'', BI Mannheim, [[1990]], {{ISBN|3-411-14172-7}}
* I.-J. Sackmann et al: ''Our Sun. III. Present and Future'', Astrophysical Journal, 418, S. 457?468, Nov. 1993 [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1993ApJ...418..457S Online-Version]
* C. Bounama, W. v. Bloh, S. Franck: ''Das Ende des Raumschiffs Erde'', Spektrum der Wissenschaft, Oktober 2004, S. 52?59
* L. J. November, S. Koutchmy: ''White-Light Coronal Dark Threads and Density Fine Structure'', Astrophysical Journal, 466, S. 512ff, Juli 1996 (Korona-Profil).
* Wolfgang Mattig, ''Die Sonne'', Beck'sche Reihe Bd.2001, {{ISBN|3-406-39001-3}}


== Web Links ==

{{Wiktionary|Sun}} {{Commonscat|Sun}} {{Wikiquote|Sonne}}

* [ http://www.planet wissen.de/pw/Artikel,,,, C6F9AB9E612E83FBE030DB95FBC306B2,,,,,,,.html planet knowledge:'' sun'' ]
* [ http://www.wissen news.de/solar system/sonne.php know news.de - the sun our Heimatgestirn ] (dt.)
* [http://www.raumfahrer.net/astronomie/solarsystem/sonne.shtml Raumfahrer.net: The sun]
* [ http://astronomie solar system.de/ astronomy solar system.de ]
* [ http://photojournal.jpl.nasa.gov/target/Sun pictures of the sun ]

=== videos ===

* [[material video]]: [ http://www.br-online.de/cgi-bin/ravi?v=alpha/centauri/v/&f=990704.rm alpha centauri:'' from where the sun has its energy?'' ]

{{Solar System table}}