Editing Asteroid belt (section)

==History of observation==
[[File:JKepler.jpg|thumb|upright|In 1596, [[Johannes Kepler]]'s sense of proportion for the planetary orbits led him to believe that an invisible planet lay between the orbits of Mars and Jupiter.<ref>{{cite journal | title=The origins and legacy of 'Kepler's Gap' | last=Cunningham | first=Clifford J. | author-link=Clifford Cunningham | journal=Journal of Astronomical History and Heritage | volume=25 | issue=3 | pages=439–456 | date=September 2022 | doi=10.3724/SP.J.1440-2807.2022.03.02 | bibcode=2022JAHH...25..439C | s2cid=256570746 }}</ref>]]
{{see also|Definition of planet|List of minor planets}}

In 1596, [[Johannes Kepler]] wrote, "Between Mars and Jupiter, I place a planet," in his ''[[Mysterium Cosmographicum]]'', stating his prediction that a planet would be found there.<ref>{{cite web|url=https://dawn.jpl.nasa.gov/DawnClassrooms/1_hist_dawn/history_discovery/Exploration/fb_jupiter_mars.pdf |archive-url=https://web.archive.org/web/20051121154941/http://dawn.jpl.nasa.gov/DawnClassrooms/1_hist_dawn/history_discovery/Exploration/fb_jupiter_mars.pdf |archive-date=2005-11-21 |url-status=live|title=Dawn: Between Jupiter and Mars [sic], I Place a Planet|website=[[Jet Propulsion Laboratory]]|publisher=[[NASA]]|last1=Davis|first1=Phil|last2=Dunford|first2=Bill|last3=Boeck|first3=Moore}}</ref> While analyzing [[Tycho Brahe]]'s data, Kepler thought that too large a gap existed between the orbits of Mars and Jupiter to fit his own model of where planetary orbits should be found.<ref>{{cite book|url=https://books.google.com/books?id=9TMcWJwAyFkC&pg=PA5|title=The Dawn Mission to Minor Planets 4 Vesta and 1 Ceres|editor1-first=Christopher|editor1-last=Russell|editor2-first=Carol|editor2-last= Raymond | year=2012 | publisher=[[Springer Science+Business Media]]|page=5|isbn=978-1-4614-4902-7}}</ref>

In an anonymous footnote to his 1766 translation of [[Charles Bonnet]]'s ''Contemplation de la Nature'',<ref name="asteroids">{{cite web|title=When Did the Asteroids Become Minor Planets? | last=Hilton | first=J. |work=US Naval Observatory (USNO) | year=2001 | url=http://www.usno.navy.mil/USNO/astronomical-applications/astronomical-information-center/minor-planets|access-date=2007-10-01|url-status=dead|archive-url=https://web.archive.org/web/20120406222551/http://www.usno.navy.mil/USNO/astronomical-applications/astronomical-information-center/minor-planets/|archive-date=2012-04-06}}</ref> the astronomer [[Johann Daniel Titius]] of [[Wittenberg]]<ref name="Dawn">{{cite web|title=Dawn: A Journey to the Beginning of the Solar System|work=Space Physics Center: UCLA | year=2005 | url=http://www-ssc.igpp.ucla.edu/dawn/background.html|access-date=2007-11-03|url-status=dead|archive-url=https://archive.today/20120524184638/http://www-ssc.igpp.ucla.edu/dawn/background.html|archive-date=2012-05-24}}</ref><ref name="Hoskin">{{cite web | title=Bode's Law and the Discovery of Ceres | last=Hoskin | first=Michael | work=Churchill College, Cambridge | url=http://www.astropa.unipa.it/versione_inglese/Hystory/BODE%27S_LAW.htm | access-date=2010-07-12 | archive-date=May 10, 2008 | archive-url=https://archive.today/20080510092601/http://www.astropa.unipa.it/versione_inglese/Hystory/BODE'S_LAW.htm | url-status=bot: unknown }}</ref> noted an apparent pattern in the layout of the planets, now known as the [[Titius-Bode Law]]. If one began a numerical sequence at 0, then included 3, 6, 12, 24, 48, etc., doubling each time, and added four to each number and divided by 10, this produced a remarkably close approximation to the radii of the orbits of the known planets as measured in [[astronomical units]], ''provided'' one allowed for a "missing planet" (equivalent to 24 in the sequence) between the orbits of Mars (12) and Jupiter (48). In his footnote, Titius declared, "But should the Lord Architect have left that space empty? Not at all."<ref name="Dawn" /> When [[William Herschel]] discovered [[Uranus]] in 1781, the planet's orbit closely matched the law, leading some astronomers to conclude that a planet had to be between the orbits of Mars and Jupiter.<ref name=Nieto_2014>{{cite book
 | title=The Titius-Bode Law of Planetary Distances, Its History and Theory
 | first=Michael Martin | last=Nieto | year=2014
 | page=17 | isbn=978-1-4831-5936-2 | publisher=Elsevier Science
 | url=https://books.google.com/books?id=NneoBQAAQBAJ&pg=PA17
}}</ref>

[[File:Costanzo Angelini, L'astronomo Piazzi 1825 ca.jpg|thumb|upright|[[Giuseppe Piazzi]], discoverer of Ceres, the largest object in the asteroid belt: Ceres was known as a planet, but later reclassified as an asteroid and from 2006 as a dwarf planet.]]
On January 1, 1801, [[Giuseppe Piazzi]], chairman of astronomy at the [[University of Palermo]], Sicily, found a tiny moving object in an orbit with exactly the radius predicted by this pattern. He dubbed it "Ceres", after the [[Ceres (Roman mythology)|Roman goddess]] of the harvest and patron of Sicily. Piazzi initially believed it to be a comet, but its lack of a [[Coma (cometary)|coma]] suggested it was a planet.<ref name="police">{{cite journal|title=Call the police! The story behind the discovery of the asteroids|journal=[[Astronomy Now]]|issue=June 2007|pages=60–61}}</ref>
Thus, the aforementioned pattern predicted the [[Semi-major axis|semimajor axes]] of all eight planets of the time (Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, and Uranus).  Concurrent with the discovery of Ceres, an informal group of 24 astronomers dubbed the "[[celestial police]]" was formed under the invitation of [[Franz Xaver von Zach]] with the express purpose of finding additional planets; they focused their search for them in the region between Mars and Jupiter where the [[Titius–Bode law]] predicted there should be a planet.<ref>{{cite web |last1=Winterburn |first1=Emily |title=Discovering asteroid Vesta: the story of the Celestial Police |url=https://www.skyatnightmagazine.com/space-science/asteroid-vesta-discovery-celestial-police/ |website=Sky at Night Magazine |publisher=BBC |access-date=18 October 2022|date = 10 March 2021}}</ref><ref>{{cite news |last1=McWilliams |first1=Brendan |title=Fruitless search of the Celestial Police |url=https://www.irishtimes.com/news/fruitless-search-of-the-celestial-police-1.320465 |access-date=18 October 2022 |work=Irish Times |date=31 July 2001}}</ref>

About 15 months later, [[Heinrich Wilhelm Matthias Olbers|Heinrich Olbers]], a member of the celestial police, discovered a second object in the same region, Pallas. Unlike the other known planets, Ceres and Pallas remained points of light even under the highest telescope magnifications instead of resolving into discs. Apart from their rapid movement, they appeared indistinguishable from [[star]]s.<ref name="serendipity"/>

Accordingly, in 1802, [[William Herschel]] suggested they be placed into a separate category, named "asteroids", after the [[Ancient Greek language|Greek]] ''asteroeides'', meaning "star-like".<ref>{{cite web
| first=Douglas| last=Harper| title=Asteroid| year=2010
| work=Online Etymology Dictionary| publisher=Etymology Online
| url=http://www.etymonline.com/index.php?search=asteroid&searchmode=none
| access-date=2011-04-15 }}</ref><ref name="aster-root">{{cite web
| last= DeForest | first=Jessica
| year = 2000
| url = http://www.msu.edu/~defores1/gre/roots/gre_rts_afx2.htm
| title = Greek and Latin Roots
| publisher = Michigan State University
| access-date = 2007-07-25
| archive-url= https://web.archive.org/web/20070812155525/http://www.msu.edu/~defores1/gre/roots/gre_rts_afx2.htm| archive-date= 12 August 2007 | url-status= live}}</ref> Upon completing a series of observations of Ceres and Pallas, he concluded,<ref>{{cite journal
|title=William Herschel and the First Two Asteroids
| last=Cunningham | first=Clifford
|place=Dance Hall Observatory, Ontario | year=1984
|bibcode=1984MPBu...11....3C
|volume=11
|page=3
|journal=The Minor Planet Bulletin}}
</ref>
<blockquote>
Neither the appellation of planets nor that of comets can with any propriety of language be given to these two stars ... They resemble small stars so much as hardly to be distinguished from them. From this, their asteroidal appearance, if I take my name, and call them Asteroids; reserving for myself, however, the liberty of changing that name, if another, more expressive of their nature, should occur.
</blockquote>

By 1807, further investigation revealed two new objects in the region: [[3 Juno|Juno]] and [[4 Vesta|Vesta]].<ref name="serendipity">{{cite web
|author = Staff
| year = 2002
|url = http://dawn.jpl.nasa.gov/DawnCommunity/flashbacks/fb_06.asp
|title = Astronomical Serendipity
|publisher = NASA JPL
|access-date = 2007-04-20
|url-status = dead
|archive-url = https://web.archive.org/web/20120206235537/http://dawn.jpl.nasa.gov/DawnCommunity/flashbacks/fb_06.asp
|archive-date = 2012-02-06
}}
</ref> The burning of [[Lilienthal, Lower Saxony|Lilienthal]] in the [[Napoleonic wars]], where the main body of work had been done,<ref name=Elkins>{{cite book
| first=Linda T.
| last=Elkins-Tanton
| year=2011
| title=Asteroids, Meteorites, and Comets
| edition=Revised
| publisher=Facts on File
| location=New York
| isbn=978-0-8160-7696-3
| oclc=1054369860
| page=}}{{page needed|date=October 2022}}</ref> brought this first period of discovery to a close.<ref name="serendipity" />

Despite Herschel's coinage, for several decades it remained common practice to refer to these objects as planets<ref name="asteroids" /> and to prefix their names with numbers representing their sequence of discovery: 1&nbsp;Ceres, 2&nbsp;Pallas, 3&nbsp;Juno, 4&nbsp;Vesta. In 1845, though, the astronomer [[Karl Ludwig Hencke]] detected a fifth object ([[5&nbsp;Astraea]]) and, shortly thereafter, new objects were found at an accelerating rate. Counting them among the planets became increasingly cumbersome. Eventually, they were dropped from the planet list (as first suggested by [[Alexander von Humboldt]] in the early 1850s) and Herschel's coinage, "asteroids", gradually came into common use.<ref name="asteroids" />

The discovery of [[Neptune]] in 1846 led to the discrediting of the Titius–Bode law in the eyes of scientists because its orbit was nowhere near the predicted position. To date, no scientific explanation for the law has been given, and astronomers' consensus regards it as a coincidence.<ref>{{cite web
|title=Is it a coincidence that most of the planets fall within the Titius-Bode law's boundaries?
|work=astronomy.com
|url=http://www.astronomy.com/magazine/ask-astro/2006/10/is-it-a-coincidence-that-most-of-the-planets-fall-within-the-titius-bode-laws-boundaries
|access-date=2014-01-22}}
</ref>

[[File:951 Gaspra.jpg|right|thumb|[[951&nbsp;Gaspra]], the first asteroid imaged by a spacecraft, as viewed during ''[[Galileo (spacecraft)|Galileo]]'''s 1991 flyby; colors are exaggerated]]
The expression "asteroid belt" came into use in the early 1850s, although pinpointing who coined the term is difficult. The first English use seems to be in the 1850 translation (by [[Elise Otté]]) of Alexander von Humboldt's ''[[Cosmos (Humboldt)|Cosmos]]'':<ref>{{cite book | last=von Humboldt | first=Alexander | title=Cosmos: A Sketch of a Physical Description of the Universe|volume=1|publisher=Harper & Brothers|location= New York | year= 1850 | page=44|isbn=978-0-8018-5503-0}}</ref> "[...] and the regular appearance, about the 13th of November and the 11th of August, of shooting stars, which probably form part of a belt of asteroids intersecting the Earth's orbit and moving with planetary velocity". Another early appearance occurred in [[Robert James Mann]]'s ''A Guide to the Knowledge of the Heavens'':<ref>{{cite book | last=Mann | first=Robert James | title=A Guide to the Knowledge of the Heavens|publisher=Jarrold | year=1852 | page=171}} and 1853, p. 216</ref> "The orbits of the asteroids are placed in a wide belt of space, extending between the extremes of [...]". The American astronomer [[Benjamin Peirce]] seems to have adopted that terminology and to have been one of its promoters.<ref name="ENPJ1857">{{cite journal
|url=https://books.google.com/books?id=hhQAAAAAMAAJ&pg=PA191
|title=Further Investigation relative to the form, the magnitude, the mass, and the orbit of the Asteroid Planets
|journal=The Edinburgh New Philosophical Journal
|volume=5
|date=January–April 1857
|page=191}}: "[Professor Peirce] then observed that the analogy between the ring of Saturn and the belt of the asteroids was worthy of notice."</ref>

Over 100 asteroids had been located by mid-1868, and in 1891, the introduction of [[astrophotography]] by [[Max Wolf]] accelerated the rate of discovery.<ref>{{cite web
| first = David W.
| last = Hughes
| year = 2007
| url = http://www.open2.net/sciencetechnologynature/planetsbeyond/asteroids/history.html
| title = A Brief History of Asteroid Spotting
| publisher = BBC
| access-date = 2007-04-20
| archive-date = 2011-06-11
| archive-url = https://web.archive.org/web/20110611093414/http://www.open2.net/sciencetechnologynature/planetsbeyond/asteroids/history.html
| url-status = dead
}}</ref> A total of 1,000 asteroids had been found by 1921,<ref>{{cite book
| last1=Moore | first1=Patrick | last2=Rees | first2=Robin | year=2011
| page=156| title=Patrick Moore's Data Book of Astronomy
| edition=2nd| publisher=Cambridge University Press
| isbn=978-0-521-89935-2
}}</ref> 10,000 by 1981,<ref>{{cite video
| people=Manley, Scott| date=August 25, 2010
| title=Asteroid Discovery from 1980 to 2010
| work=YouTube
| url=https://www.youtube.com/watch?v=S_d-gs0WoUw
| archive-url=https://ghostarchive.org/varchive/youtube/20211030/S_d-gs0WoUw| archive-date=2021-10-30| access-date=2011-04-15
}}{{cbignore}}</ref> and 100,000 by 2000.<ref>{{cite web
| title=MPC Archive Statistics
| publisher=IAU Minor Planet Center
| url=http://www.minorplanetcenter.org/iau/lists/ArchiveStatistics.html
| access-date=2011-04-04 }}</ref> Modern asteroid survey systems now use automated means to locate new minor planets in ever-increasing numbers.

On 22 January 2014, [[European Space Agency]] (ESA) scientists reported the detection, for the first definitive time, of [[water vapor]] on Ceres, the largest object in the asteroid belt.<ref name="KüppersO'Rourke2014">{{cite journal |last1=Küppers |first1=Michael |last2=O'Rourke |first2=Laurence |last3=Bockelée-Morvan |first3=Dominique|author3-link=Dominique Bockelée-Morvan |last4=Zakharov |first4=Vladimir |last5=Lee |first5=Seungwon |last6=von Allmen |first6=Paul |last7=Carry |first7=Benoît |last8=Teyssier |first8=David |last9=Marston |first9=Anthony |last10=Müller |first10=Thomas |last11=Crovisier |first11=Jacques |last12=Barucci |first12=M. Antonietta |last13=Moreno |first13=Raphael |title=Localized sources of water vapour on the dwarf planet (1) Ceres |journal=Nature |volume=505 |issue=7484 | year=2014 |pages=525–527 |issn=0028-0836 |doi=10.1038/nature12918 |bibcode = 2014Natur.505..525K |pmid=24451541 |s2cid=4448395}}</ref> The detection was made by using the [[Far-infrared astronomy|far-infrared abilities]] of the [[Herschel Space Observatory]].<ref name="NASA-20140122">{{cite web |last1=Harrington |first1=J. D. |title=Herschel Telescope Detects Water on Dwarf Planet – Release 14-021 |url=http://www.nasa.gov/press/2014/january/herschel-telescope-detects-water-on-dwarf-planet |date=22 January 2014 |work=[[NASA]] |access-date=22 January 2014 }}</ref> The finding was unexpected because [[comet]]s, not asteroids, are typically considered to "sprout jets and plumes". According to one of the scientists, "The lines are becoming more and more blurred between comets and asteroids".<ref name="NASA-20140122"/>