Editing Solar System (section)

== Discovery and exploration ==
{{Main|Discovery and exploration of the Solar System}}
[[File:Apparent retrograde motion of Mars in 2003.gif|thumb|The motion of 'lights' moving across the sky is the basis of the classical definition of planets: wandering stars.]]
Humanity's knowledge of the Solar System has grown incrementally over the centuries. Up to the [[Late Middle Ages]]–[[Renaissance]], astronomers from Europe to India believed Earth to [[Geocentric model|be stationary at the center]] of the universe<ref>{{Cite book |last=Orrell |first=David |url=https://books.google.com/books?id=mNMsa18vTpsC&pg=PA25 |title=Truth Or Beauty: Science and the Quest for Order |date=2012 |publisher=Yale University Press |isbn=978-0300186611 |pages=25–27 |access-date=13 May 2022 |archive-url=https://web.archive.org/web/20220730084322/https://www.google.com/books/edition/Truth_Or_Beauty/mNMsa18vTpsC?gbpv=1&pg=PA25 |archive-date=30 July 2022 |url-status=live}}</ref> and categorically different from the divine or ethereal objects that moved through the sky. Although the [[Ancient Greece|Greek]] philosopher [[Aristarchus of Samos]] had speculated on a [[heliocentric]] reordering of the cosmos, [[Nicolaus Copernicus]] was the first person known to have developed [[Copernican heliocentrism|a mathematically predictive heliocentric system]].<ref>{{Cite magazine |last=Rufus |first=W. C. |date=1923 |title=The astronomical system of Copernicus |magazine=[[Popular Astronomy (US magazine)|Popular Astronomy]] |volume=31 |page=510 |bibcode=1923PA.....31..510R}}</ref><ref>{{Cite book |last=Weinert |first=Friedel |url=https://archive.org/details/copernicusdarwin00wein |title=Copernicus, Darwin, & Freud: revolutions in the history and philosophy of science |date=2009 |publisher=[[Wiley-Blackwell]] |isbn=978-1-4051-8183-9 |page=[https://archive.org/details/copernicusdarwin00wein/page/n29 21] |url-access=limited}}</ref>

Heliocentrism did not triumph immediately over geocentrism, but the work of Copernicus had its champions, notably [[Johannes Kepler]]. Using a heliocentric model that improved upon Copernicus by allowing orbits to be elliptical, and the precise observational data of [[Tycho Brahe]], Kepler produced the ''[[Rudolphine Tables]]'', which enabled accurate computations of the positions of the then-known planets. [[Pierre Gassendi]] used them to predict a [[transit of Mercury]] in 1631, and [[Jeremiah Horrocks]] did the same for a [[transit of Venus]] in 1639. This provided a strong vindication of heliocentrism and Kepler's elliptical orbits.<ref>{{Cite book |last=LoLordo |first=Antonia |url=https://www.worldcat.org/oclc/182818133 |title=Pierre Gassendi and the Birth of Early Modern Philosophy |date=2007 |publisher=Cambridge University Press |isbn=978-0-511-34982-9 |location=New York |pages=12, 27 |oclc=182818133 |access-date=1 April 2022 |archive-url=https://web.archive.org/web/20220420161223/https://www.worldcat.org/title/pierre-gassendi-and-the-birth-of-early-modern-philosophy/oclc/182818133 |archive-date=20 April 2022 |url-status=live}}</ref><ref>{{Cite journal |last1=Athreya |first1=A. |last2=Gingerich |first2=O. |date=December 1996 |title=An Analysis of Kepler's Rudolphine Tables and Implications for the Reception of His Physical Astronomy |journal=Bulletin of the American Astronomical Society |volume=28 |issue=4 |page=1305 |bibcode=1996AAS...189.2404A}}<!--|accessdate=26 December 2013--></ref>

In the 17th century, [[Galileo Galilei|Galileo]] publicized the use of the telescope in astronomy; he and [[Simon Marius]] independently discovered that Jupiter had four satellites in orbit around it.<ref>{{Cite journal |last=Pasachoff |first=Jay M. |date=May 2015 |title=Simon Marius's Mundus Iovialis: 400th Anniversary in Galileo's Shadow |url=http://journals.sagepub.com/doi/10.1177/0021828615585493 |url-status=live |journal=Journal for the History of Astronomy |language=en |volume=46 |issue=2 |pages=218–234 |bibcode=2015JHA....46..218P |doi=10.1177/0021828615585493 |issn=0021-8286 |s2cid=120470649 |archive-url=https://web.archive.org/web/20211127213209/https://journals.sagepub.com/doi/10.1177/0021828615585493 |archive-date=27 November 2021 |access-date=1 April 2022}}</ref> [[Christiaan Huygens]] followed on from these observations by discovering Saturn's moon [[Titan (moon)|Titan]] and the shape of the [[rings of Saturn]].<ref>{{Cite web |date=8 December 2012 |title=Christiaan Huygens: Discoverer of Titan |url=https://www.esa.int/About_Us/ESA_history/Christiaan_Huygens_Discoverer_of_Titan |url-status=live |archive-url=https://web.archive.org/web/20191206001920/http://www.esa.int/About_Us/ESA_history/Christiaan_Huygens_Discoverer_of_Titan |archive-date=6 December 2019 |access-date=27 October 2010 |website=ESA Space Science |publisher=The European Space Agency}}</ref> In 1677, [[Edmond Halley]] observed a transit of Mercury across the Sun, leading him to realize that observations of the [[solar parallax]] of a planet (more ideally using the transit of Venus) could be used to [[Trigonometry|trigonometrically]] determine the distances between Earth, [[Venus]], and the Sun.<ref>{{Cite conference |last=Chapman |first=Allan |date=April 2005 |editor-last=Kurtz |editor-first=D. W. |title=Jeremiah Horrocks, William Crabtree, and the Lancashire observations of the transit of Venus of 1639 |conference=Transits of Venus: New Views of the Solar System and Galaxy, Proceedings of IAU Colloquium #196, held 7–11 June 2004 in Preston, U.K. |publisher=Cambridge University Press |publication-place=Cambridge |volume=2004 |pages=3–26 |bibcode=2005tvnv.conf....3C |doi=10.1017/S1743921305001225 |doi-access=free |journal=Proceedings of the International Astronomical Union}}</ref> Halley's friend [[Isaac Newton]], in his magisterial ''[[Philosophiæ Naturalis Principia Mathematica|Principia Mathematica]]'' of 1687, demonstrated that celestial bodies are not quintessentially different from Earthly ones: the same [[Newton's laws of motion|laws of motion]] and of [[Newton's law of universal gravitation|gravity]] apply on Earth and in the skies.<ref name=":0"/>{{Rp|page=142}}
[[File:The Solar System, with the orbits of 5 remarkable comets. LOC 2013593161 (cropped).jpg|thumb|Solar system diagram by [[Emanuel Bowen]] in 1747, when neither Uranus, Neptune, nor the asteroid belts had yet been discovered. Orbits of planets are to scale, but the orbits of moons and the sizes of bodies are not.]]
The term "Solar System" entered the English language by 1704, when [[John Locke]] used it to refer to the Sun, planets, and comets.<ref>See, for example:
* {{Cite web |title=solar |url=https://www.etymonline.com/word/solar |url-status=live |archive-url=https://web.archive.org/web/20220318002833/https://www.etymonline.com/word/solar |archive-date=18 March 2022 |access-date=17 March 2022 |website=[[Online Etymology Dictionary]]}}
* {{Cite OED|solar system}}
* {{Cite book |last=Locke |first=John |url=https://books.google.com/books?id=Ni9bAAAAcAAJ |title=Elements of Natural Philosophy ... To which are added. Some Thoughts concerning Reading and Study for a Gentleman. By the same author. With prefatory remarks by P. Des Maizeaux |date=1754 |publisher=R. Taylor |page=8 |language=en |author-link=John Locke |orig-date=1720 |access-date=18 March 2022 |archive-date=18 March 2022 |archive-url=https://web.archive.org/web/20220318005707/https://books.google.com/books?id=Ni9bAAAAcAAJ&newbks=0 |url-status=live }} Posthumous publication.</ref> In 1705, Halley realized that repeated sightings of [[Halley's Comet|a comet]] were of the same object, returning regularly once every 75–76&nbsp;years. This was the first evidence that anything other than the planets repeatedly orbited the Sun,<ref>{{Cite book |last1=Festou |first1=M. C. |title=Comets II |last2=Keller |first2=H. U. |last3=Weaver |first3=H. A. |date=2004 |publisher=University of Arizona Press |isbn=978-0816524501 |publication-place=Tucson |pages=3–16 |chapter=A brief conceptual history of cometary science |bibcode=2004come.book....3F |access-date=7 April 2022 |chapter-url=https://books.google.com/books?id=ehA8EAAAQBAJ&pg=PA4 |archive-url=https://web.archive.org/web/20220420161222/https://www.google.com/books/edition/Comets_II/ehA8EAAAQBAJ?gbpv=1&pg=PA4 |archive-date=20 April 2022 |url-status=live}}</ref> though [[Seneca the Younger|Seneca]] had theorized this about comets in the 1st century.<ref>{{Cite book |last1=Sagan |first1=Carl |url=https://books.google.com/books?id=LhkoowKFaTsC |title=Comet |last2=Druyan |first2=Ann |publisher=Random House |year=1997 |isbn=978-0-3078-0105-0 |location=New York |pages=26–27, 37–38 |author-link=Carl Sagan |author-link2=Ann Druyan |access-date=28 June 2021 |archive-url=https://web.archive.org/web/20210615020250/https://books.google.com/books?id=LhkoowKFaTsC |archive-date=15 June 2021 |url-status=live}}</ref> Careful observations of the 1769 transit of Venus allowed astronomers to calculate the average Earth–Sun distance as {{Convert|93726900|mi|km}}, only 0.8% greater than the modern value.<ref>{{Cite journal |last=Teets |first=Donald |date=December 2003 |title=Transits of Venus and the Astronomical Unit |url=http://www.maa.org/sites/default/files/pdf/pubs/mm_dec03-Venus.pdf |url-status=live |journal=Mathematics Magazine |volume=76 |pages=335–348 |doi=10.1080/0025570X.2003.11953207 |jstor=3654879 |s2cid=54867823 |archive-url=https://web.archive.org/web/20220203080207/https://www.maa.org/sites/default/files/pdf/pubs/mm_dec03-Venus.pdf |archive-date=3 February 2022 |access-date=3 April 2022 |number=5}}</ref>

[[Uranus]], having occasionally been observed since 1690 and possibly from antiquity, was recognized to be a planet orbiting beyond Saturn by 1783.<ref>{{Cite journal |last=Bourtembourg |first=René |date=2013 |title=Was Uranus Observed by Hipparchos? |journal=Journal for the History of Astronomy |volume=44 |issue=4 |pages=377–387 |bibcode=2013JHA....44..377B |doi=10.1177/002182861304400401 |s2cid=122482074}}</ref> In 1838, [[Friedrich Bessel]] successfully measured a [[stellar parallax]], an apparent shift in the position of a star created by Earth's motion around the Sun, providing the first direct, experimental proof of heliocentrism.<ref>{{Cite book |last=Di Bari |first=Pasquale |url=https://books.google.com/books?id=hPm7DwAAQBAJ&pg=PA4 |title=Cosmology and the Early Universe |date=2018 |publisher=CRC Press |isbn=978-1351020138 |pages=3–4}}</ref> [[Neptune]] was identified as a planet some years later, in 1846, thanks to its gravitational pull causing a slight but detectable variation in the orbit of Uranus.<ref>{{Cite journal |last1=Bhatnagar |first1=Siddharth |last2=Vyasanakere |first2=Jayanth P. |last3=Murthy |first3=Jayant |date=May 2021 |title=A geometric method to locate Neptune |url=https://aapt.scitation.org/doi/10.1119/10.0003349 |url-status=live |journal=American Journal of Physics |language=en |volume=89 |issue=5 |pages=454–458 |arxiv=2102.04248 |bibcode=2021AmJPh..89..454B |doi=10.1119/10.0003349 |issn=0002-9505 |s2cid=231846880 |archive-url=https://web.archive.org/web/20211129125826/https://aapt.scitation.org/doi/10.1119/10.0003349 |archive-date=29 November 2021 |access-date=1 April 2022}}</ref> [[Perihelion precession of Mercury|Mercury's orbital anomaly]] observations led to searches for [[Vulcan (hypothetical planet)|Vulcan]], a planet interior of Mercury, but these attempts were quashed with [[Albert Einstein]]'s theory of [[general relativity]] in 1915.<ref name="Clemence">{{cite journal |last=Clemence |first=G. M. |date=1947 |title=The Relativity Effect in Planetary Motions |journal=Reviews of Modern Physics |volume=19 |issue=4 |pages=361–364 |bibcode=1947RvMP...19..361C |doi=10.1103/RevModPhys.19.361}} [http://www.mathpages.com/rr/s6-02/6-02.htm (math)]</ref>

In the 20th century, humans began their space exploration around the Solar System, starting with placing [[Space telescope|telescopes in space]] since the 1960s.<ref>{{Cite web |last=Garner |first=Rob |date=10 December 2018 |title=50th Anniversary of OAO 2: NASA's 1st Successful Stellar Observatory |url=http://www.nasa.gov/feature/goddard/2018/nasa-s-first-stellar-observatory-oao-2-turns-50 |url-status=live |archive-url=https://web.archive.org/web/20211229231948/https://www.nasa.gov/feature/goddard/2018/nasa-s-first-stellar-observatory-oao-2-turns-50 |archive-date=29 December 2021 |access-date=20 April 2022 |website=NASA}}</ref> By 1989, all eight planets have been visited by space probes.<ref name="FactSheet">{{cite web |title=Fact Sheet |url=https://voyager.jpl.nasa.gov/news/factsheet.html |url-status=live |archive-url=https://web.archive.org/web/20161129230752/http://voyager.jpl.nasa.gov/news/factsheet.html |archive-date=29 November 2016 |access-date=3 March 2016 |publisher=JPL}}</ref> Probes have returned samples from comets<ref>{{Cite magazine |last=Woo |first=Marcus |date=20 November 2014 |title=This Is What It Sounded Like When We Landed on a Comet |url=https://www.wired.com/2014/11/sounded-like-landed-comet |archive-url=https://web.archive.org/web/20141123021050/https://www.wired.com/2014/11/sounded-like-landed-comet |archive-date=23 November 2014 |access-date=20 April 2022 |magazine=Wired}}</ref> and asteroids,<ref>{{Cite web |last=Marks |first=Paul |date=3 December 2014 |title=Hayabusa 2 probe begins journey to land on an asteroid |url=https://www.newscientist.com/article/dn26650-hayabusa-2-probe-begins-journey-to-land-on-an-asteroid |url-status=live |archive-url=https://web.archive.org/web/20220211062123/https://www.newscientist.com/article/dn26650-hayabusa-2-probe-begins-journey-to-land-on-an-asteroid |archive-date=11 February 2022 |access-date=20 April 2022 |website=New Scientist |language=en-US}}</ref> as well as flown through the [[Sun's corona]]<ref>{{Cite web |date=14 December 2021 |title=NASA's Parker Solar Probe becomes first spacecraft to 'touch' the sun |url=https://www.cnn.com/2021/12/14/world/nasa-parker-solar-probe-sun-scn/index.html |url-status=live |archive-url=https://web.archive.org/web/20211214235239/https://www.cnn.com/2021/12/14/world/nasa-parker-solar-probe-sun-scn/index.html |archive-date=14 December 2021 |access-date=15 December 2021 |website=CNN}}</ref> and visited two dwarf planets ([[Pluto]] and [[Ceres (dwarf planet)|Ceres]]).<ref>{{Cite news |last1=Corum |first1=Jonathan |last2=Gröndahl |first2=Mika |last3=Parshina-Kottas |first3=Yuliya |date=13 July 2015 |title=New Horizons' Pluto Flyby |url=https://www.nytimes.com/interactive/2015/07/14/science/space/pluto-flyby.html,%20https://www.nytimes.com/interactive/2015/07/14/science/space/pluto-flyby.html |access-date=20 April 2022 |work=The New York Times |language=en-US |issn=0362-4331}}</ref><ref name="NASA-20180907">{{cite web |last1=McCartney |first1=Gretchen |last2=Brown |first2=Dwayne |last3=Wendel |first3=JoAnna |date=7 September 2018 |title=Legacy of NASA's Dawn, Near the End of its Mission |url=https://www.jpl.nasa.gov/news/news.php?feature=7231 |access-date=8 September 2018 |work=[[NASA]]}}</ref> To save on fuel, some space missions make use of [[Gravity assist|gravity assist maneuvers]], such as the two [[Voyager program|''Voyager'' probes]] accelerating when flying by planets in the outer Solar System<ref name=":7">{{Cite web |title=Basics of Spaceflight: A Gravity Assist Primer |url=https://science.nasa.gov/learn/basics-of-space-flight/primer/ |access-date=2 May 2024 |website=science.nasa.gov|date=20 July 2023 }}</ref> and the [[Parker Solar Probe]] decelerating closer towards the Sun after its flyby of Venus.<ref>{{Cite web |date=4 October 2018 |title=Parker Solar Probe Changed the Game Before it Even Launched - NASA |url=https://www.nasa.gov/solar-system/parker-solar-probe-changed-the-game-before-it-even-launched/ |access-date=2 May 2024 |language=en-US}}</ref>

Humans have landed on the Moon during the [[Apollo program]] in the 1960s and 1970s<ref>{{Cite book |url=https://archive.org/details/guinnessworldrec00vari/page/13 |title=Guinness World Records 2010 |publisher=[[Bantam Books]] |year=2010 |isbn=978-0-553-59337-2 |editor-last=Glenday |editor-first=Craig |editor-link=Craig Glenday |location=New York}}</ref> and will return to the Moon in the 2020s with the [[Artemis program]].<ref name="sn-20230313">{{cite web |last=Foust |first=Jeff |date=13 March 2023 |title=NASA planning to spend up to $1 billion on space station deorbit module |url=https://spacenews.com/nasa-planning-to-spend-up-to-1-billion-on-space-station-deorbit-module/ |access-date=13 March 2023 |work=[[SpaceNews]]}}</ref> Discoveries in the 20th and 21st century has prompted the [[Definition of planet|redefinition of the term ''planet'']] in 2006, hence the demotion of Pluto to a dwarf planet,<ref name="NYT-20220118">{{cite news |last=Chang |first=Kenneth |date=18 January 2022 |title=Quiz - Is Pluto A Planet? - Who doesn't love Pluto? It shares a name with the Roman god of the underworld and a Disney dog. But is it a planet? - Interactive |url=https://www.nytimes.com/interactive/2022/science/is-pluto-a-planet.html |accessdate=18 January 2022 |work=[[The New York Times]]}}</ref> and further interest in [[trans-Neptunian object]]s.<ref name=":02">{{cite web |last=Spaceflight |first=Leonard David |date=9 January 2019 |title=A Wild 'Interstellar Probe' Mission Idea Is Gaining Momentum |url=https://www.space.com/42935-nasa-interstellar-probe-mission-idea.html |access-date=23 September 2019 |website=Space.com |language=en}}</ref>