Camianpedia - User contributions [en]

Sun

2018-06-16T19:00:06Z

185.133.180.159: GFDLCC BY-SA 3.0

bugti.sab

== Physics of the Sun ==
=== Origin ===
Scientists think that the Sun started from a very large cloud of dust and small bits of ice about 4.567 [[billion]] years ago.<ref name="Connelly2012">{{cite journal |title=The absolute chronology and thermal processing of solids in the solar protoplanetary disk |journal=[[Science (journal)|Science]] |last=Connelly, James N. ''et al'' |volume=338 |issue=6107 |pages=651–655 |date= 2012 |doi=10.1126/science.1226919 |bibcode=2012Sci...338..651C |pmid=23118187}}</ref>

At the center of that huge cloud, [[gravity]] caused the material to build up into a ball. Once this got big enough, the huge pressure inside started a [[fusion reaction]]. The energy this released caused that ball to heat and shine.

The energy [[radiation|radiated]] from the Sun pushed away the rest of the cloud from itself, and the planets formed from the rest of this cloud

=== How it works ===
* At its very center, [[hydrogen]] [[atom]]s collide together at great [[temperature]] and [[pressure]] so that they fuse to form atoms of [[helium]]. This process is called [[nuclear fusion]].
The sun can also be used as a source of [[solar energy|energy]]. That energy is [[Solar energy]].

== Orbit ==
The sun and everything that orbits it is located in the [[Milky Way]]. As the sun orbits it takes everything in the solar system. The sun moves at 820,000 km an hour. At that speed its still 230 million years for a full orbit.

== Visible features ==
Since the Sun is all gas, surface features come and go. If the Sun is viewed through a special solar [[telescope]], dark areas called [[sunspot]]s can be seen. These areas are caused by the Sun's [[magnetic field]]. The sunspots only look dark because the rest of the Sun is very bright.

Some [[space telescopes]], including the ones that orbit the Sun have seen huge [[arch]]es of the Sun's matter extend suddenly from the Sun. These are called solar prominences. Solar prominences come in many different shapes and sizes. Some of them are so large that the Earth could fit inside of them, and a few are shaped like hands. [[Solar flare]]s also come and go.

Sunspots, prominences and flares become rare, and then numerous, and then rare again, every 11 years.

=== Photosphere ===
This is the surface of the Sun. The light that the Earth receives from the Sun is [[radiation|radiated]] from this layer. Below this layer, the Sun is [[Opacity|opaque]], or not [[transparent]] to light.

== Atmosphere ==
Five layers make up the [[atmosphere]] of the Sun. The chromosphere, transition region, and corona are much hotter than the outer photosphere surface of the Sun.<ref name=Abhyankar1977/> It is believed that [[Alfvén wave]]s may pass through to heat the corona.<ref>
{{Cite journal|last=De Pontieu B. ''et al''|title=Chromospheric Alfvénic waves strong enough to power the solar wind|journal=Science|volume=318 |issue=5856 |pages=1574–77|year=2007|doi=10.1126/science.1151747|pmid=18063784|ref=harv|bibcode = 2007Sci...318.1574D }}</ref>

The '''minimum temperature zone''', the coolest layer of the Sun, is about {{val|500|u=km}} above the photosphere. It has a temperature of about {{val|4100|ul=K}}.<ref name=Abhyankar1977>{{Cite journal|last=Abhyankar K.D.|title=A survey of the solar atmospheric models|year=1977|journal=Bull. Astr. Soc. India|volume=5|bibcode=1977BASI....5...40A|pages=40–44|url=http://prints.iiap.res.in/handle/2248/510|ref=harv}}</ref> This part of the Sun is cool enough to allow simple molecules such as [[carbon monoxide]] and water to form. These molecules can be seen on the Sun with special instruments called spectroscopes.<ref name=Solanki1994>{{Cite journal|last=Solanki S.K; Livingston W. & Ayres T|title=New light on the heart of darkness of the solar chromosphere |year=1994|journal=Science|pmid=17748350|volume=263|issue=5143|pages=64–66|doi=10.1126/science.263.5143.64|ref=harv|bibcode = 1994Sci...263...64S }}</ref>

The '''chromosphere''' is the first layer of the Sun which can be seen, especially during a [[solar eclipse]] when the moon is covering most of the Sun and blocking the brightest light.

The '''solar transition region''' is the part of the Sun's atmosphere, between the chromosphere and outer part called the [[corona]].<ref name=MSFC>{{cite web|title=The Transition Region|url=http://solarscience.msfc.nasa.gov/t_region.shtml|work=Solar Physics, NASA Marshall Space Flight Center|publisher=NASA}}</ref> It can be seen from [[outer space|space]] using telescopes that can sense [[ultraviolet]] light. The transition is between two very different layers. In the bottom part it touches the photosphere and gravity shapes the features. At the top, the transition layer touches the corona.

The '''[[corona]]''' is the outer atmosphere of the Sun and is much bigger than the rest of the Sun. The corona continuously expands into space forming the [[solar wind]], which fills all the Solar System.<ref name=Russell2001/> The average temperature of the corona and solar wind is about 1,000,000–2,000,000 [[Kelvin|K]]. In the hottest regions it is 8,000,000–20,000,000 K.<ref name=Erdelyi2007/> We do not understand why the corona is so hot.<ref name=Russell2001>{{Cite book|last=Russell|first=C.T.|title=Space weather (Geophysical Monograph)|year=2001|publisher=American Geophysical Union|chapter=Solar wind and interplanetary magnetic filed: A tutorial|editors=Song, Paul; Singer, Howard J. and Siscoe, George L.|isbn=978-0-87590-984-4|pages=73–88|url=http://www-ssc.igpp.ucla.edu/personnel/russell/papers/SolWindTutorial.pdf|format=PDF}}</ref><ref name=Erdelyi2007>Erdèlyi R. & Ballai I. 2007. Heating of the solar and stellar coronae: a review. ''Astron. Nachr''. '''328''' (8): 726–733</ref> It can be seen during a [[solar eclipse]] or with an instrument called a coronagraph.

The '''[[heliosphere]]''' is the thin outer atmosphere of the Sun, filled with the [[solar wind]] [[Plasma (physics)|plasma]]. It extends out past the orbit of [[Pluto]] to the [[Heliopause (astronomy)|heliopause]], where it forms a boundary where it collides with the [[interstellar medium]].<ref>
{{cite press
|url=http://www.spaceref.com/news/viewpr.html?pid=16394
|title=The distortion of the Heliosphere: our interstellar magnetic compass
|year=2005
|publisher=[[European Space Agency]]
|accessdate=2006-03-22
}}</ref>

== Eclipses ==
A solar [[eclipse]] appears when the moon is between the Earth and Sun. The last partial eclipse seen in Britain was on the 21st of August, 2017.

A [[lunar eclipse]] happens when the moon passes through the shadow of the Earth which can only occur during a full moon.The number of lunar eclipses in a single year can range from 0 to 3. Partial eclipses slightly outnumber total eclipses by 7 to 6.<ref>[http://www.mreclipse.com/Special/LEprimer.html]</ref>

== Fate of the Sun ==
[[Astrophysics|Astrophysicists]] say our Sun is a [[G-type main-sequence star]] in the middle of its [[stellar evolution|life]]. In a billion years or so, increased solar energy will boil away the [[Earth's atmosphere]] and oceans. In a few more billion years, they think the Sun will get bigger and become a [[red giant]] star. The Sun would be up to 250 times its current size, as big as 1.4 [[astronomic unit|AU]] and will swallow up the earth.

[[Earth]]'s fate is still a bit of a mystery. In the long term, the Earth's future depends on the Sun, and the Sun is going to be fairly stable for the next 5 [[billion]] years.<ref>[http://faculty.wcas.northwestern.edu/~infocom/The%20Website/evolution.html The Sun's evolution]</ref><ref>Goldsmith D. & Owen T. 2001. ''The search for life in the universe''. University Science Books, p. 96. ISBN 978-1-891389-16-0</ref> Calculations suggest that the Earth might move to a wider orbit. This is because about 30% of the Sun's mass will blow away in the [[solar wind]]. However, in the very long term the Earth will probably be destroyed as the Sun increases in size. Stars like the Sun become [[red giant]]s at a later stage.<ref>Schröder K.-P. & Smith R.C. 2008. Distant future of the Sun and Earth revisited. ''Monthly Notices of the Royal Astronomical Society'' '''386''' (1): 155–163. [http://mnras.oxfordjournals.org/content/386/1/155]</ref> The Sun will expand beyond orbits of Mercury, Venus, and probably Earth. In any event, the Earth's ocean and air would have vanished before the Sun gets to that stage.

After the Sun reaches a point where it can no longer get bigger, it will lose its layers and form a [[planetary nebula]]. Eventually, the Sun will shrink into a [[white dwarf]]. Then, over several hundred billion or even a trillion years, the Sun would fade into a [[black dwarf]].

== More reading ==
*{{cite book|first=Kenneth R.|last=Lang|title=The Cambridge Encyclopedia of the Sun|publisher=Cambridge University Press|date=2001|isbn=9780521780933}}

== References ==
{{reflist}}
*https://solarsystem.nasa.gov/planets/sun/indepth

{{Spoken Wikipedia|Sun.ogg|19 July 2006}}
{{commons}}
{{wikijunior|The Sun|Solar System/The Sun}}
{{Solar System}}

[[Category:Basic English 850 words]]
[[Category:Stars]]
[[Category:Solar System]]

Sun

2018-06-16T18:57:20Z

185.133.180.159: GFDLCC BY-SA 3.0

{{for|the newspaper|The Sun (newspaper)}}
{{Infobox
| bodystyle = border-collapse:collapse
| title = The Sun [[Image:Sun symbol.svg|25px]]
| image = [[File:The Sun by the Atmospheric Imaging Assembly of NASA's Solar Dynamics Observatory - 20100819.jpg|290px]]
| headerstyle = background:#FCC857
| labelstyle = padding:2px
| datastyle = padding:2px

| header1 = Observation data
| label2 = Average distance from [[Earth]]
| data2 = {{val|1.496|e=8|u=km}} 8 min 19 s at [[speed of light|light speed]]
| label3 = [[Apparent magnitude|Visual brightness]] (''V'')
| data3 = −26.74<ref name=nssdc>{{cite web|last=Williams|first=D. R. |date=1 July 2013 |title=Sun Fact Sheet |url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html |publisher=[[NASA Goddard Space Flight Center]] |accessdate=12 August 2013}}</ref>
| label4 = [[Absolute magnitude|True brightness]]
| data4 = 4.83<ref name=nssdc />
| label7 = [[Angular size]]
| data7 = 31.6–32.7′<ref>{{cite web |title=Eclipse 99: Frequently Asked Questions |url=http://education.gsfc.nasa.gov/eclipse/pages/faq.html |publisher=[[NASA]] |accessdate=24 October 2010}}</ref>
| label8 = Adjective
| data8 = Solar
| header10 = [[Orbit]] and [[rotation]]
| label11 = Average distance from [[Milky Way]] center
| data11 = ≈ {{val|2.7|e=17|u=km}} {{nowrap|{{val|fmt=commas|27200|ul=light-years}}}}
| label13 = [[Velocity]]
| data13 = ≈ {{val|220|u=km/s}} (orbit around the center of the Milky Way) ≈ {{val|20|u=km/s}} (relative to average velocity of other stars nearby) ≈ {{val|370|u=km/s}}<ref>{{cite journal |last=Hinshaw |first=G. |display-authors=etal |date=2009 |title=Five-year Wilkinson Microwave Anisotropy Probe observations: data processing, sky maps, and basic results |journal=[[The Astrophysical Journal Supplement Series]] |volume=180 |issue=2 |pages=225–245 |arxiv=0803.0732 |bibcode=2009ApJS..180..225H |doi=10.1088/0067-0049/180/2/225}}</ref> (relative to the [[Cosmic microwave background radiation#CMBR dipole anisotropy|cosmic microwave background]])
| label14 = [[Axial tilt|Obliquity]]
| data14 = 7.25°<ref name=nssdc/> (to the [[ecliptic]]) 67.23° (to the [[galactic plane]])
| label15 = Rotation velocity
| data15 = {{val|7.189|e=3|u=km/h}}<ref name="sse"/>

| header20 = Physical characteristics
| label21 = Equatorial [[radius]]
| data21 = {{nowrap|{{val|fmt=commas|696342|65|u=km}}}}<ref name=arxiv1203_4898>{{cite journal |last1=Emilio |first1=M. |last2=Kuhn |first2=J. R. |last3=Bush |first3=R. I. |last4=Scholl |first4=I. F. |date=2012 |title=Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits |journal=[[The Astrophysical Journal]] |volume=750 |issue=2 |page=135 |arxiv=1203.4898 |bibcode=2012ApJ...750..135E |doi=10.1088/0004-637X/750/2/135}}</ref> 109 × Earth<ref name=sse/>
| label22 = Equatorial [[circumference]]
| data22 = {{val|4.379|e=6|u=km}}<ref name=sse/> 109 × Earth<ref name=sse>{{cite web |title=Solar System Exploration: Planets: Sun: Facts & Figures |url=http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric |archiveurl=https://web.archive.org/web/20080102034758/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric |archivedate=2 January 2008 |publisher=[[NASA]]
}}</ref>
| label23 = [[Flattening]]
| data23 = {{val|9|e=-6}}
| label24 = [[Surface area]]
| data24 = {{val|6.09|e=12|u=km2}}<ref name=sse/> {{nowrap|{{val|fmt=commas|12000}}}} × Earth<ref name=sse/>
| label25 = [[Volume]]
| data25 = {{val|1.41|e=18|u=km3}}<ref name=sse/> {{nowrap|{{val|fmt=commas|1300000}}}} × Earth
| label26 = [[Mass]]
| data26 = {{val|1.98855|.00025|e=30|u=kg}}<ref name=nssdc/> {{nowrap|{{val|fmt=commas|333000}}}} × Earth<ref name=nssdc/>
| label27 = Average [[density]]
| data27 = {{val|1.408|u=g/cm3}}<ref name=nssdc/><ref name=sse/><ref>{{cite web |last=Ko |first=M. |date=1999 |title=Density of the Sun |url=http://hypertextbook.com/facts/1999/MayKo.shtml |editor=Elert, G. |work=The Physics Factbook}}</ref> {{val|0.255}} × Earth<ref name=nssdc/><ref name=sse/>
| label29 = [[Surface gravity]]
| data29 = {{val|274.0|u=m/s2}}<ref name=nssdc/> {{val|27.94|u=[[g-force|''g'']]}} {{nowrap|{{val|fmt=commas|27542.29|u=''[[cgs]]''}}}} 28 × Earth<ref name=sse/>
| label30 = [[Escape velocity]] (from the surface)
| data30 = {{val|617.7|u=km/s}}<ref name=sse/> 55 × Earth<ref name=sse/>
| label31 = Temperature
| data31 = Center: {{val|1.57|e=7|u=K}}<ref name=nssdc/> [[Photosphere]]: {{nowrap|{{val|fmt=commas|5778|ul=K}}}}<ref name=nssdc/> [[Corona]]: ≈ {{val|5|e=6|u=K}}
| label32 = [[Luminosity]] (Lsol)
| data32 = {{val|3.846|e=26|ul=W}}<ref name=nssdc/>
| label34 = Age
| data34 = ≈4.6 billion years<ref name="Bonanno">{{Cite journal |last=Bonanno |first=A. |last2=Schlattl |first2=H. |last3=Paternò |first3=L. |date=2008 |title=The age of the Sun and the relativistic corrections in the EOS |journal=[[Astronomy and Astrophysics]] |volume=390 |issue=3 |pages=1115–1118 |arxiv=astro-ph/0204331 |bibcode=2002A&A...390.1115B |doi=10.1051/0004-6361:20020749 |ref=harv}}</ref><ref>{{Cite journal|url=//www.sciencemag.org/content/338/6107/651.full|title=The Absolute Chronology and Thermal Processing of Solids in the Solar Protoplanetary Disk|date=2 November 2012|accessdate=17 March 2014|doi=10.1126/science.1226919 |journal=Science|volume=338 |issue= 6107 |pages=651–655|bibcode = 2012Sci...338..651C |pmid=23118187}}</ref>
}}
[[File:India Goa Fort Chapora Chapora River.jpg|thumb|250px|The Sun as it is seen from [[Earth]]]]

The '''Sun''' in the center of our solar system is a yellow dwarf star. It gives off [[energy]] as [[electromagnetic radiation]]. That includes light, [[infra-red]] energy (heat), [[ultraviolet light]] and [[radio]] waves. It also gives off a stream of [[particle]]s, which reaches Earth as "[[solar wind]]". The source of all this energy is the reaction in the star which turns [[hydrogen]] into [[helium]] and makes huge amounts of energy.

The Sun is a star like many others in our [[Milky Way]] [[galaxy]]. It has existed for a little over 4.5 [[billion]] years, and is going to continue for at least as long. The Sun is about a hundred times as wide as the Earth. It has a mass of {{val|1.9891|e=30|u=kg}}, which is 333,000 times the mass of the Earth. The Earth can also fit inside the Sun 1.3 million times.

== Physics of the Sun ==
bugti.sab

=== How it works ===
* At its very center, [[hydrogen]] [[atom]]s collide together at great [[temperature]] and [[pressure]] so that they fuse to form atoms of [[helium]]. This process is called [[nuclear fusion]].
The sun can also be used as a source of [[solar energy|energy]]. That energy is [[Solar energy]].

== Orbit ==
The sun and everything that orbits it is located in the [[Milky Way]]. As the sun orbits it takes everything in the solar system. The sun moves at 820,000 km an hour. At that speed its still 230 million years for a full orbit.

== Visible features ==
Since the Sun is all gas, surface features come and go. If the Sun is viewed through a special solar [[telescope]], dark areas called [[sunspot]]s can be seen. These areas are caused by the Sun's [[magnetic field]]. The sunspots only look dark because the rest of the Sun is very bright.

Some [[space telescopes]], including the ones that orbit the Sun have seen huge [[arch]]es of the Sun's matter extend suddenly from the Sun. These are called solar prominences. Solar prominences come in many different shapes and sizes. Some of them are so large that the Earth could fit inside of them, and a few are shaped like hands. [[Solar flare]]s also come and go.

Sunspots, prominences and flares become rare, and then numerous, and then rare again, every 11 years.

=== Photosphere ===
This is the surface of the Sun. The light that the Earth receives from the Sun is [[radiation|radiated]] from this layer. Below this layer, the Sun is [[Opacity|opaque]], or not [[transparent]] to light.

== Atmosphere ==
Five layers make up the [[atmosphere]] of the Sun. The chromosphere, transition region, and corona are much hotter than the outer photosphere surface of the Sun.<ref name=Abhyankar1977/> It is believed that [[Alfvén wave]]s may pass through to heat the corona.<ref>
{{Cite journal|last=De Pontieu B. ''et al''|title=Chromospheric Alfvénic waves strong enough to power the solar wind|journal=Science|volume=318 |issue=5856 |pages=1574–77|year=2007|doi=10.1126/science.1151747|pmid=18063784|ref=harv|bibcode = 2007Sci...318.1574D }}</ref>

The '''minimum temperature zone''', the coolest layer of the Sun, is about {{val|500|u=km}} above the photosphere. It has a temperature of about {{val|4100|ul=K}}.<ref name=Abhyankar1977>{{Cite journal|last=Abhyankar K.D.|title=A survey of the solar atmospheric models|year=1977|journal=Bull. Astr. Soc. India|volume=5|bibcode=1977BASI....5...40A|pages=40–44|url=http://prints.iiap.res.in/handle/2248/510|ref=harv}}</ref> This part of the Sun is cool enough to allow simple molecules such as [[carbon monoxide]] and water to form. These molecules can be seen on the Sun with special instruments called spectroscopes.<ref name=Solanki1994>{{Cite journal|last=Solanki S.K; Livingston W. & Ayres T|title=New light on the heart of darkness of the solar chromosphere |year=1994|journal=Science|pmid=17748350|volume=263|issue=5143|pages=64–66|doi=10.1126/science.263.5143.64|ref=harv|bibcode = 1994Sci...263...64S }}</ref>

The '''chromosphere''' is the first layer of the Sun which can be seen, especially during a [[solar eclipse]] when the moon is covering most of the Sun and blocking the brightest light.

The '''solar transition region''' is the part of the Sun's atmosphere, between the chromosphere and outer part called the [[corona]].<ref name=MSFC>{{cite web|title=The Transition Region|url=http://solarscience.msfc.nasa.gov/t_region.shtml|work=Solar Physics, NASA Marshall Space Flight Center|publisher=NASA}}</ref> It can be seen from [[outer space|space]] using telescopes that can sense [[ultraviolet]] light. The transition is between two very different layers. In the bottom part it touches the photosphere and gravity shapes the features. At the top, the transition layer touches the corona.

The '''[[corona]]''' is the outer atmosphere of the Sun and is much bigger than the rest of the Sun. The corona continuously expands into space forming the [[solar wind]], which fills all the Solar System.<ref name=Russell2001/> The average temperature of the corona and solar wind is about 1,000,000–2,000,000 [[Kelvin|K]]. In the hottest regions it is 8,000,000–20,000,000 K.<ref name=Erdelyi2007/> We do not understand why the corona is so hot.<ref name=Russell2001>{{Cite book|last=Russell|first=C.T.|title=Space weather (Geophysical Monograph)|year=2001|publisher=American Geophysical Union|chapter=Solar wind and interplanetary magnetic filed: A tutorial|editors=Song, Paul; Singer, Howard J. and Siscoe, George L.|isbn=978-0-87590-984-4|pages=73–88|url=http://www-ssc.igpp.ucla.edu/personnel/russell/papers/SolWindTutorial.pdf|format=PDF}}</ref><ref name=Erdelyi2007>Erdèlyi R. & Ballai I. 2007. Heating of the solar and stellar coronae: a review. ''Astron. Nachr''. '''328''' (8): 726–733</ref> It can be seen during a [[solar eclipse]] or with an instrument called a coronagraph.

The '''[[heliosphere]]''' is the thin outer atmosphere of the Sun, filled with the [[solar wind]] [[Plasma (physics)|plasma]]. It extends out past the orbit of [[Pluto]] to the [[Heliopause (astronomy)|heliopause]], where it forms a boundary where it collides with the [[interstellar medium]].<ref>
{{cite press
|url=http://www.spaceref.com/news/viewpr.html?pid=16394
|title=The distortion of the Heliosphere: our interstellar magnetic compass
|year=2005
|publisher=[[European Space Agency]]
|accessdate=2006-03-22
}}</ref>

== Eclipses ==
A solar [[eclipse]] appears when the moon is between the Earth and Sun. The last partial eclipse seen in Britain was on the 21st of August, 2017.

A [[lunar eclipse]] happens when the moon passes through the shadow of the Earth which can only occur during a full moon.The number of lunar eclipses in a single year can range from 0 to 3. Partial eclipses slightly outnumber total eclipses by 7 to 6.<ref>[http://www.mreclipse.com/Special/LEprimer.html]</ref>

== Fate of the Sun ==
[[Astrophysics|Astrophysicists]] say our Sun is a [[G-type main-sequence star]] in the middle of its [[stellar evolution|life]]. In a billion years or so, increased solar energy will boil away the [[Earth's atmosphere]] and oceans. In a few more billion years, they think the Sun will get bigger and become a [[red giant]] star. The Sun would be up to 250 times its current size, as big as 1.4 [[astronomic unit|AU]] and will swallow up the earth.

[[Earth]]'s fate is still a bit of a mystery. In the long term, the Earth's future depends on the Sun, and the Sun is going to be fairly stable for the next 5 [[billion]] years.<ref>[http://faculty.wcas.northwestern.edu/~infocom/The%20Website/evolution.html The Sun's evolution]</ref><ref>Goldsmith D. & Owen T. 2001. ''The search for life in the universe''. University Science Books, p. 96. ISBN 978-1-891389-16-0</ref> Calculations suggest that the Earth might move to a wider orbit. This is because about 30% of the Sun's mass will blow away in the [[solar wind]]. However, in the very long term the Earth will probably be destroyed as the Sun increases in size. Stars like the Sun become [[red giant]]s at a later stage.<ref>Schröder K.-P. & Smith R.C. 2008. Distant future of the Sun and Earth revisited. ''Monthly Notices of the Royal Astronomical Society'' '''386''' (1): 155–163. [http://mnras.oxfordjournals.org/content/386/1/155]</ref> The Sun will expand beyond orbits of Mercury, Venus, and probably Earth. In any event, the Earth's ocean and air would have vanished before the Sun gets to that stage.

After the Sun reaches a point where it can no longer get bigger, it will lose its layers and form a [[planetary nebula]]. Eventually, the Sun will shrink into a [[white dwarf]]. Then, over several hundred billion or even a trillion years, the Sun would fade into a [[black dwarf]].

== More reading ==
*{{cite book|first=Kenneth R.|last=Lang|title=The Cambridge Encyclopedia of the Sun|publisher=Cambridge University Press|date=2001|isbn=9780521780933}}

== References ==
{{reflist}}
*https://solarsystem.nasa.gov/planets/sun/indepth

{{Spoken Wikipedia|Sun.ogg|19 July 2006}}
{{commons}}
{{wikijunior|The Sun|Solar System/The Sun}}
{{Solar System}}

[[Category:Basic English 850 words]]
[[Category:Stars]]
[[Category:Solar System]]

Sun

2018-06-16T18:56:28Z

185.133.180.159: bugti.sabGFDL CC BY-SA 3.0

Sun

2018-06-16T18:52:44Z

185.133.180.159: bugti.sabCC BY-SA 3.0

{bugti.sab.

== Physics of the Sun ==
=== Origin ===
Scientists think that the Sun started from a very large cloud of dust and small bits of ice about 4.567 [[billion]] years ago.<ref name="Connelly2012">{{cite journal |title=The absolute chronology and thermal processing of solids in the solar protoplanetary disk |journal=[[Science (journal)|Science]] |last=Connelly, James N. ''et al'' |volume=338 |issue=6107 |pages=651–655 |date= 2012 |doi=10.1126/science.1226919 |bibcode=2012Sci...338..651C |pmid=23118187}}</ref>

At the center of that huge cloud, [[gravity]] caused the material to build up into a ball. Once this got big enough, the huge pressure inside started a [[fusion reaction]]. The energy this released caused that ball to heat and shine.

The energy [[radiation|radiated]] from the Sun pushed away the rest of the cloud from itself, and the planets formed from the rest of this cloud

=== How it works ===
* At its very center, [[hydrogen]] [[atom]]s collide together at great [[temperature]] and [[pressure]] so that they fuse to form atoms of [[helium]]. This process is called [[nuclear fusion]].
The sun can also be used as a source of [[solar energy|energy]]. That energy is [[Solar energy]].

== Orbit ==
The sun and everything that orbits it is located in the [[Milky Way]]. As the sun orbits it takes everything in the solar system. The sun moves at 820,000 km an hour. At that speed its still 230 million years for a full orbit.

== Visible features ==
Since the Sun is all gas, surface features come and go. If the Sun is viewed through a special solar [[telescope]], dark areas called [[sunspot]]s can be seen. These areas are caused by the Sun's [[magnetic field]]. The sunspots only look dark because the rest of the Sun is very bright.

Some [[space telescopes]], including the ones that orbit the Sun have seen huge [[arch]]es of the Sun's matter extend suddenly from the Sun. These are called solar prominences. Solar prominences come in many different shapes and sizes. Some of them are so large that the Earth could fit inside of them, and a few are shaped like hands. [[Solar flare]]s also come and go.

Sunspots, prominences and flares become rare, and then numerous, and then rare again, every 11 years.

=== Photosphere ===
This is the surface of the Sun. The light that the Earth receives from the Sun is [[radiation|radiated]] from this layer. Below this layer, the Sun is [[Opacity|opaque]], or not [[transparent]] to light.

== Atmosphere ==
Five layers make up the [[atmosphere]] of the Sun. The chromosphere, transition region, and corona are much hotter than the outer photosphere surface of the Sun.<ref name=Abhyankar1977/> It is believed that [[Alfvén wave]]s may pass through to heat the corona.<ref>
{{Cite journal|last=De Pontieu B. ''et al''|title=Chromospheric Alfvénic waves strong enough to power the solar wind|journal=Science|volume=318 |issue=5856 |pages=1574–77|year=2007|doi=10.1126/science.1151747|pmid=18063784|ref=harv|bibcode = 2007Sci...318.1574D }}</ref>

The '''minimum temperature zone''', the coolest layer of the Sun, is about {{val|500|u=km}} above the photosphere. It has a temperature of about {{val|4100|ul=K}}.<ref name=Abhyankar1977>{{Cite journal|last=Abhyankar K.D.|title=A survey of the solar atmospheric models|year=1977|journal=Bull. Astr. Soc. India|volume=5|bibcode=1977BASI....5...40A|pages=40–44|url=http://prints.iiap.res.in/handle/2248/510|ref=harv}}</ref> This part of the Sun is cool enough to allow simple molecules such as [[carbon monoxide]] and water to form. These molecules can be seen on the Sun with special instruments called spectroscopes.<ref name=Solanki1994>{{Cite journal|last=Solanki S.K; Livingston W. & Ayres T|title=New light on the heart of darkness of the solar chromosphere |year=1994|journal=Science|pmid=17748350|volume=263|issue=5143|pages=64–66|doi=10.1126/science.263.5143.64|ref=harv|bibcode = 1994Sci...263...64S }}</ref>

The '''chromosphere''' is the first layer of the Sun which can be seen, especially during a [[solar eclipse]] when the moon is covering most of the Sun and blocking the brightest light.

The '''solar transition region''' is the part of the Sun's atmosphere, between the chromosphere and outer part called the [[corona]].<ref name=MSFC>{{cite web|title=The Transition Region|url=http://solarscience.msfc.nasa.gov/t_region.shtml|work=Solar Physics, NASA Marshall Space Flight Center|publisher=NASA}}</ref> It can be seen from [[outer space|space]] using telescopes that can sense [[ultraviolet]] light. The transition is between two very different layers. In the bottom part it touches the photosphere and gravity shapes the features. At the top, the transition layer touches the corona.

The '''[[corona]]''' is the outer atmosphere of the Sun and is much bigger than the rest of the Sun. The corona continuously expands into space forming the [[solar wind]], which fills all the Solar System.<ref name=Russell2001/> The average temperature of the corona and solar wind is about 1,000,000–2,000,000 [[Kelvin|K]]. In the hottest regions it is 8,000,000–20,000,000 K.<ref name=Erdelyi2007/> We do not understand why the corona is so hot.<ref name=Russell2001>{{Cite book|last=Russell|first=C.T.|title=Space weather (Geophysical Monograph)|year=2001|publisher=American Geophysical Union|chapter=Solar wind and interplanetary magnetic filed: A tutorial|editors=Song, Paul; Singer, Howard J. and Siscoe, George L.|isbn=978-0-87590-984-4|pages=73–88|url=http://www-ssc.igpp.ucla.edu/personnel/russell/papers/SolWindTutorial.pdf|format=PDF}}</ref><ref name=Erdelyi2007>Erdèlyi R. & Ballai I. 2007. Heating of the solar and stellar coronae: a review. ''Astron. Nachr''. '''328''' (8): 726–733</ref> It can be seen during a [[solar eclipse]] or with an instrument called a coronagraph.

The '''[[heliosphere]]''' is the thin outer atmosphere of the Sun, filled with the [[solar wind]] [[Plasma (physics)|plasma]]. It extends out past the orbit of [[Pluto]] to the [[Heliopause (astronomy)|heliopause]], where it forms a boundary where it collides with the [[interstellar medium]].<ref>
{{cite press
|url=http://www.spaceref.com/news/viewpr.html?pid=16394
|title=The distortion of the Heliosphere: our interstellar magnetic compass
|year=2005
|publisher=[[European Space Agency]]
|accessdate=2006-03-22
}}</ref>

== Eclipses ==
A solar [[eclipse]] appears when the moon is between the Earth and Sun. The last partial eclipse seen in Britain was on the 21st of August, 2017.

A [[lunar eclipse]] happens when the moon passes through the shadow of the Earth which can only occur during a full moon.The number of lunar eclipses in a single year can range from 0 to 3. Partial eclipses slightly outnumber total eclipses by 7 to 6.<ref>[http://www.mreclipse.com/Special/LEprimer.html]</ref>

== Fate of the Sun ==
[[Astrophysics|Astrophysicists]] say our Sun is a [[G-type main-sequence star]] in the middle of its [[stellar evolution|life]]. In a billion years or so, increased solar energy will boil away the [[Earth's atmosphere]] and oceans. In a few more billion years, they think the Sun will get bigger and become a [[red giant]] star. The Sun would be up to 250 times its current size, as big as 1.4 [[astronomic unit|AU]] and will swallow up the earth.

[[Earth]]'s fate is still a bit of a mystery. In the long term, the Earth's future depends on the Sun, and the Sun is going to be fairly stable for the next 5 [[billion]] years.<ref>[http://faculty.wcas.northwestern.edu/~infocom/The%20Website/evolution.html The Sun's evolution]</ref><ref>Goldsmith D. & Owen T. 2001. ''The search for life in the universe''. University Science Books, p. 96. ISBN 978-1-891389-16-0</ref> Calculations suggest that the Earth might move to a wider orbit. This is because about 30% of the Sun's mass will blow away in the [[solar wind]]. However, in the very long term the Earth will probably be destroyed as the Sun increases in size. Stars like the Sun become [[red giant]]s at a later stage.<ref>Schröder K.-P. & Smith R.C. 2008. Distant future of the Sun and Earth revisited. ''Monthly Notices of the Royal Astronomical Society'' '''386''' (1): 155–163. [http://mnras.oxfordjournals.org/content/386/1/155]</ref> The Sun will expand beyond orbits of Mercury, Venus, and probably Earth. In any event, the Earth's ocean and air would have vanished before the Sun gets to that stage.

After the Sun reaches a point where it can no longer get bigger, it will lose its layers and form a [[planetary nebula]]. Eventually, the Sun will shrink into a [[white dwarf]]. Then, over several hundred billion or even a trillion years, the Sun would fade into a [[black dwarf]].

== More reading ==
*{{cite book|first=Kenneth R.|last=Lang|title=The Cambridge Encyclopedia of the Sun|publisher=Cambridge University Press|date=2001|isbn=9780521780933}}

== References ==
{{reflist}}
*https://solarsystem.nasa.gov/planets/sun/indepth

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