Editing Solar System (section)

== Sun ==
{{Main|Sun}}
[[File:The Sun in white light.jpg|thumb|alt=White ball of plasma|The Sun in true white color]]

The Sun is the Solar System's star and by far its most massive component. Its large mass (332,900 [[Earth mass]]es),<ref>{{Cite web |title=Sun: Facts & Figures |url=http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric |url-status=dead |archive-url=https://web.archive.org/web/20080102034758/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric |archive-date=2 January 2008 |access-date=14 May 2009 |publisher=NASA}}</ref> which comprises 99.86% of all the mass in the Solar System,<ref name="Woolfson00">{{Cite journal |last=Woolfson |first=M. |date=2000 |title=The origin and evolution of the solar system |journal=[[Astronomy & Geophysics]] |volume=41 |issue=1 |page=12 |bibcode=2000A&G....41a..12W |doi=10.1046/j.1468-4004.2000.00012.x |doi-access=free}}</ref> produces temperatures and densities in its [[solar core|core]] high enough to sustain nuclear fusion of hydrogen into helium.<ref>{{Cite book |last=Zirker |first=Jack B. |url=https://archive.org/details/journeyfromcente0000zirk |title=Journey from the Center of the Sun |date=2002 |publisher=[[Princeton University Press]] |isbn=978-0-691-05781-1 |pages=[https://archive.org/details/journeyfromcente0000zirk/page/120 120–127] |url-access=registration}}</ref> This releases an enormous amount of [[energy]], mostly [[radiant energy|radiated]] into [[outer space|space]] as [[electromagnetic radiation]] peaking in [[visible light]].<ref>{{Cite web |title=What Color is the Sun? |work=NASA |url=https://eclipse2017.nasa.gov/what-color-sun |access-date=6 April 2024 |archive-date=26 April 2024 |archive-url=https://web.archive.org/web/20240426130849/https://eclipse2017.nasa.gov/what-color-sun |url-status=live }}</ref><ref>{{Cite web |title=What Color is the Sun? |url=http://solar-center.stanford.edu/SID/activities/GreenSun.html |url-status=live |archive-url=https://web.archive.org/web/20171030154449/http://solar-center.stanford.edu/SID/activities/GreenSun.html |archive-date=30 October 2017 |access-date=23 May 2016 |publisher=[[Stanford University|Stanford]] Solar Center}}</ref>

Because the Sun fuses hydrogen at its core, it is a main-sequence star. More specifically, it is a [[G-type main-sequence star|G2-type main-sequence star]], where the type designation refers to its [[effective temperature]]. Hotter main-sequence stars are more luminous but shorter lived. The Sun's temperature is intermediate between that of the [[O-type main-sequence star|hottest stars]] and that of the coolest stars. Stars brighter and hotter than the Sun are rare, whereas substantially dimmer and cooler stars, known as [[red dwarf]]s, make up about 75% of the [[Fusor (astronomy)|fusor]] stars in the [[Milky Way]].<ref>{{Cite journal |last1=Mejías |first1=Andrea |last2=Minniti |first2=Dante |last3=Alonso-García |first3=Javier |last4=Beamín |first4=Juan Carlos |last5=Saito |first5=Roberto K. |last6=Solano |first6=Enrique |year=2022 |title=VVVX near-IR photometry for 99 low-mass stars in the Gaia EDR3 Catalog of Nearby Stars |journal=Astronomy & Astrophysics |volume=660 |pages=A131 |arxiv=2203.00786 |bibcode=2022A&A...660A.131M |doi=10.1051/0004-6361/202141759 |s2cid=246842719}}</ref>

The Sun is a [[Population I stars|population I star]], having formed in the [[spiral arm]]s of the [[Milky Way]] galaxy. It has a higher abundance of elements heavier than hydrogen and helium ("[[metallicity|metals]]" in astronomical parlance) than the older population II stars in the [[galactic bulge]] and [[Galactic halo|halo]].<ref>{{Cite journal |last1=van Albada |first1=T.S. |last2=Baker |first2=Norman |date=1973 |title=On the Two Oosterhoff Groups of Globular Clusters |journal=[[The Astrophysical Journal]] |volume=185 |pages=477–498 |bibcode=1973ApJ...185..477V |doi=10.1086/152434 |doi-access=free}}</ref> Elements heavier than hydrogen and helium were formed in the cores of ancient and exploding stars, so the first generation of stars had to die before the [[universe]] could be enriched with these atoms. The oldest stars contain few metals, whereas stars born later have more. This higher metallicity is thought to have been crucial to the Sun's development of a [[planetary system]] because the planets formed from the accretion of "metals".<ref>{{Cite journal |last=Lineweaver |first=Charles H. |date=9 March 2001 |title=An Estimate of the Age Distribution of Terrestrial Planets in the Universe: Quantifying Metallicity as a Selection Effect |journal=[[Icarus (journal)|Icarus]] |volume=151 |issue=2 |pages=307–313 |arxiv=astro-ph/0012399 |bibcode=2001Icar..151..307L |citeseerx=10.1.1.254.7940 |doi=10.1006/icar.2001.6607 |s2cid=14077895}}</ref>

{{Anchor|Interplanetary environment}}The region of space dominated by the Solar [[magnetosphere]] is the [[heliosphere]], which spans much of the Solar System. Along with [[Sunlight|light]], the Sun radiates a continuous stream of charged particles (a [[plasma (physics)|plasma]]) called the [[solar wind]]. This stream spreads outwards at speeds from {{Convert|900000|km/h|mph}} to {{Convert|2880000|km/h|mph}},<ref>{{Cite book |last=Kallenrode |first=May-Britt |url=https://www.worldcat.org/oclc/53443301 |title=Space Physics: An introduction to plasmas and particles in the heliosphere and magnetospheres |date=2004 |publisher=Springer |isbn=978-3-540-20617-0 |edition=3rd |location=Berlin |pages=150 |oclc=53443301 |access-date=1 April 2022 |archive-url=https://web.archive.org/web/20220420161223/https://www.worldcat.org/title/space-physics-an-introduction-to-plasmas-and-particles-in-the-heliosphere-and-magnetospheres/oclc/53443301 |archive-date=20 April 2022 |url-status=live}}</ref> filling the vacuum between the bodies of the Solar System. The result is a [[Vacuum|thin]], dusty atmosphere, called the [[interplanetary medium]], which extends to at least {{val|100|u=AU}}.<ref name="Voyager">{{Cite web |last=Steigerwald |first=Bill |date=24 May 2005 |title=Voyager Enters Solar System's Final Frontier |url=http://www.nasa.gov/vision/universe/solarsystem/voyager_agu.html |url-status=live |archive-url=https://web.archive.org/web/20200516082547/https://www.nasa.gov/vision/universe/solarsystem/voyager_agu.html |archive-date=16 May 2020 |access-date=2 April 2007 |website=NASA}}</ref>

Activity on the Sun's surface, such as [[solar flare]]s and [[coronal mass ejection]]s, disturbs the heliosphere, creating [[space weather]] and causing [[geomagnetic storm]]s.<ref name="SunFlip">{{Cite web |last=Phillips |first=Tony |date=15 February 2001 |title=The Sun Does a Flip |url=https://science.nasa.gov/science-news/science-at-nasa/2001/ast15feb_1 |url-status=live |archive-url=https://web.archive.org/web/20220401050813/https://science.nasa.gov/science-news/science-at-nasa/2001/ast15feb_1 |archive-date=1 April 2022 |access-date=1 April 2022 |website=NASA Science: Share the Science}}</ref> Coronal mass ejections and similar events blow a magnetic field and huge quantities of material from the surface of the Sun. The interaction of this magnetic field and material with Earth's magnetic field funnels charged particles into Earth's upper atmosphere, where its interactions create [[Aurora (astronomy)|aurorae]] seen near the [[Earth's magnetic field#Magnetic poles|magnetic poles]].<ref>{{Cite book |last1=Fraknoi |first1=Andrew |url=https://www.worldcat.org/oclc/961476196 |title=Astronomy |last2=Morrison |first2=David |last3=Wolff |first3=Sidney C. |last4=Beck |first4=John |date=2022 |publisher=[[OpenStax]] |isbn=978-1-947-17224-1 |location=Houston, Texas |chapter=15.4 Space weather |oclc=961476196 |display-authors=3 |access-date=9 March 2022 |orig-date=2016 |chapter-url=https://openstax.org/books/astronomy/pages/15-4-space-weather |archive-url=https://web.archive.org/web/20200719090803/http://worldcat.org/oclc/961476196 |archive-date=19 July 2020 |url-status=live}}</ref> The largest stable structure within the heliosphere is the [[heliospheric current sheet]], a spiral form created by the actions of the Sun's rotating magnetic field on the interplanetary medium.<ref>{{Cite web |date=22 April 2003 |title=A Star with two North Poles |url=https://science.nasa.gov/science-news/science-at-nasa/2003/22apr_currentsheet |url-status=live |archive-url=https://web.archive.org/web/20220401192948/https://science.nasa.gov/science-news/science-at-nasa/2003/22apr_currentsheet |archive-date=1 April 2022 |access-date=1 April 2022 |website=NASA Science: Share the Science}}</ref><ref>{{Cite journal |last=Riley |first=Pete |date=2002 |title=Modeling the heliospheric current sheet: Solar cycle variations |journal=[[Journal of Geophysical Research]] |volume=107 |issue=A7 |page=1136 |bibcode=2002JGRA..107.1136R |doi=10.1029/2001JA000299 |doi-access=free}}</ref>