Editing Solar System (section)

===Asteroids===
{{Main|Asteroid}}
[[File:Inner solar system objects top view for wiki.png|right|thumb|alt=Asteroid populations depicted: near-Earth asteroids, Earth trojans, Mars trojans, main asteroid belt, Jupiter trojans, Jupiter Greeks, Jupiter Hilda's triangle|Overview of the inner Solar System up to Jupiter's orbit]]Asteroids, except for the largest, Ceres, are classified as [[small Solar System bodies]] and are composed mainly of [[carbon]]aceous, refractory rocky and metallic minerals, with some ice.<ref>{{Cite web |date=2006 |title=IAU Planet Definition Committee |url=http://www.iau.org/public_press/news/release/iau0601/newspaper |url-status=dead |archive-url=https://web.archive.org/web/20090603001603/http://www.iau.org/public_press/news/release/iau0601/newspaper |archive-date=3 June 2009 |access-date=1 March 2009 |publisher=International Astronomical Union}}</ref><ref>{{Cite web |title=Are Kuiper Belt Objects asteroids? Are large Kuiper Belt Objects planets? |url=http://curious.astro.cornell.edu/question.php?number=601 |url-status=dead |archive-url=https://web.archive.org/web/20090103110110/http://curious.astro.cornell.edu/question.php?number=601 |archive-date=3 January 2009 |access-date=1 March 2009 |publisher=[[Cornell University]]}}</ref> They range from a few meters to hundreds of kilometers in size. {{Visible anchor|Asteroid groups|text=Many asteroids are divided into [[asteroid group]]s and [[Asteroid family|families]]}} based on their orbital characteristics. Some [[Minor-planet moon|asteroids have natural satellites that orbit them]], that is, asteroids that orbit larger asteroids.<ref>{{Cite journal |last1=Snodgrass |first1=Colin |last2=Agarwal |first2=Jessica |last3=Combi |first3=Michael |last4=Fitzsimmons |first4=Alan |last5=Guilbert-Lepoutre |first5=Aurelie |last6=Hsieh |first6=Henry H. |last7=Hui |first7=Man-To |last8=Jehin |first8=Emmanuel |last9=Kelley |first9=Michael S. P. |last10=Knight |first10=Matthew M. |last11=Opitom |first11=Cyrielle |date=November 2017 |title=The Main Belt Comets and ice in the Solar System |url=http://link.springer.com/10.1007/s00159-017-0104-7 |url-status=live |journal=The Astronomy and Astrophysics Review |language=en |volume=25 |issue=1 |page=5 |arxiv=1709.05549 |bibcode=2017A&ARv..25....5S |doi=10.1007/s00159-017-0104-7 |issn=0935-4956 |s2cid=7683815 |archive-url=https://web.archive.org/web/20220420161227/https://idp.springer.com/favicon.ico |archive-date=20 April 2022 |access-date=9 March 2022}}</ref>
* [[List of Mercury-crossing minor planets|Mercury-crossing asteroids]] are those with [[perihelia]] within the orbit of Mercury. At least 362 are known to date, and include the closest objects to the Sun known in the Solar System.<ref name="JPLcrosserlist">[http://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=all;obj_kind=ast;obj_numbered=all;OBJ_field=0;ORB_field=0;c1_group=ORB;c1_item=Bi;c1_op=%3C;c1_value=0.3075;table_format=HTML;max_rows=200;format_option=comp;c_fields=BgBhBiBjBnBsChAcCq;.cgifields=format_option;.cgifields=ast_orbit_class;.cgifields=table_format;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=com_orbit_class&query=1&c_sort=BiA List of asteroids with q<0.3075 AU generated by the JPL Small-Body Database Search Engine] {{Webarchive|url=https://web.archive.org/web/20160303213657/http://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=all&obj_kind=ast&obj_numbered=all&OBJ_field=0&ORB_field=0&c1_group=ORB&c1_item=Bi&c1_op=%3C&c1_value=0.3075&table_format=HTML&max_rows=200&format_option=comp&c_fields=BgBhBiBjBnBsChAcCq&.cgifields=format_option&.cgifields=ast_orbit_class&.cgifields=table_format&.cgifields=obj_kind&.cgifields=obj_group&.cgifields=obj_numbered&.cgifields=com_orbit_class&query=1&c_sort=BiA |date=3 March 2016 }} Retrieved 30 May 2012</ref> No [[vulcanoid]]s, asteroids between the orbit of Mercury and the Sun, have been discovered.<ref>{{Cite journal |last1=Durda |first1=D .D. |last2=Stern |first2=S. A. |last3=Colwell |first3=W. B. |last4=Parker |first4=J. W. |last5=Levison |first5=H. F. |last6=Hassler |first6=D. M. |date=2004 |title=A New Observational Search for Vulcanoids in SOHO/LASCO Coronagraph Images |journal=[[Icarus (journal)|Icarus]] |volume=148 |issue=1 |pages=312–315 |bibcode=2000Icar..148..312D |doi=10.1006/icar.2000.6520}}</ref><ref name="Steffl2013">{{Cite journal |last1=Steffl |first1=A. J. |last2=Cunningham |first2=N. J. |last3=Shinn |first3=A. B. |last4=Stern |first4=S. A. |date=2013 |title=A Search for Vulcanoids with the STEREO Heliospheric Imager |journal=Icarus |volume=233 |issue=1 |pages=48–56 |arxiv=1301.3804 |bibcode=2013Icar..223...48S |doi=10.1016/j.icarus.2012.11.031 |s2cid=118612132}}</ref> As of 2024, one asteroid has been discovered to orbit completely within Venus's orbit, [[594913 ꞌAylóꞌchaxnim]].<ref>{{cite journal |last1=Bolin |first1=Bryce T. |last2=Ahumada |first2=T. |last3=van Dokkum |first3=P. |last4=Fremling |first4=C. |last5=Granvik |first5=M. |last6=Hardegree-Ullmann |first6=K. K. |last7=Harikane |first7=Y. |last8=Purdum |first8=J. N. |last9=Serabyn |first9=E. |last10=Southworth |first10=J. |last11=Zhai |first11=C. |date=November 2022 |title=The discovery and characterization of (594913) 'Ayló'chaxnim, a kilometre sized asteroid inside the orbit of Venus |url=https://academic.oup.com/mnrasl/article/517/1/L49/6665933 |journal=[[Monthly Notices of the Royal Astronomical Society Letters]] |volume=517 |issue=1 |pages=L49–L54 |arxiv=2208.07253 |bibcode=2022MNRAS.517L..49B |doi=10.1093/mnrasl/slac089 |access-date=1 October 2022 |doi-access=free |archive-date=1 October 2022 |archive-url=https://web.archive.org/web/20221001070557/https://academic.oup.com/mnrasl/article/517/1/L49/6665933 |url-status=live }}</ref>
* [[Venus-crossing asteroid]]s are those that cross the orbit of Venus. There are 2,809 as of 2015.<ref name=jpello/>
* [[near-Earth object|Near-Earth asteroids]] have orbits that approach relatively close to Earth's orbit,<ref name="MorbidelliAstIII">{{Cite book |last1=Morbidelli |first1=A. |last2=Bottke |first2=W.F. |last3=Froeschlé |first3=Ch. |last4=Michel |first4=P. |date=January 2002 |editor2-last=A. Cellino |editor3-last=P. Paolicchi |editor4-last=R.P. Binzel |chapter=Origin and Evolution of Near-Earth Objects |chapter-url=http://www.boulder.swri.edu/~bottke/Reprints/Morbidelli-etal_2002_AstIII_NEOs.pdf |url-status=live |title=Asteroids III |pages=409–422 |publisher=University of Arizona Press |bibcode=2002aste.book..409M |doi=10.2307/j.ctv1v7zdn4.33 |isbn=978-0-8165-2281-1 |archive-url=https://web.archive.org/web/20170809014123/http://www.boulder.swri.edu/~bottke/Reprints/Morbidelli-etal_2002_AstIII_NEOs.pdf |archive-date=9 August 2017 |access-date=30 August 2009 |editor=W.F. Bottke Jr.}}</ref> and some of them are [[potentially hazardous object]]s because they might collide with Earth in the future.<ref name="CNEOS-Basics">{{Cite web |title=NEO Basics – Potentially Hazardous Asteroids (PHAs) |url=https://cneos.jpl.nasa.gov/about/neo_groups.html |url-status=live |archive-url=https://web.archive.org/web/20211111141623/https://cneos.jpl.nasa.gov/about/neo_groups.html |archive-date=11 November 2021 |access-date=10 March 2022 |publisher=CNEOS NASA/JPL}}</ref><ref name="NEO-groups">{{cite web |last1=Baalke |first1=Ron |title=Near-Earth Object Groups |url=http://neo.jpl.nasa.gov/neo/groups.html |url-status=dead |archive-url=https://web.archive.org/web/20020202160655/http://neo.jpl.nasa.gov/neo/groups.html |archive-date=2 February 2002 |access-date=11 November 2016 |website=[[Jet Propulsion Laboratory]] |publisher=[[NASA]]}}</ref> There are over 37,000 known as of 2024.<ref name="neo-jpl-stats">{{cite web
  |title      = Discovery Statistics – Cumulative Totals
  |date       = December 30, 2024
  |publisher  = NASA/JPL CNEOS
  |url        = https://cneos.jpl.nasa.gov/stats/totals.html
  |access-date = January 1, 2025
  |url-status = live
  |archive-url = https://web.archive.org/web/20250101175111/https://cneos.jpl.nasa.gov/stats/totals.html
  |archive-date = January 1, 2025}}</ref> A number of solar-orbiting [[meteoroid]]s were large enough to be tracked in space before striking Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of Earth.<ref name="BROWN02">{{cite news |first=Richard |last=Monastersky |title=The Call of Catastrophes |work=Science News Online |date=March 1, 1997  |url=https://www.sciencenews.org/archive/call-catastrophes |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20040313165341/http://www.sciencenews.org/pages/sn_arc97/75th/rm_essay.htm |archive-date=March 13, 2004 }}</ref>
* [[Mars-crossing asteroids]] are those with perhihelia above 1.3&nbsp;AU which cross the orbit of Mars.<ref>{{cite journal|journal=Astronomy & Astrophysics|volume=391|pages=757–765|year=2002|doi=10.1051/0004-6361:20020834|title=Spectral properties of Mars-crossers and near-Earth objects|author=C. A. Angeli - D. Lazzaro|issue=2 }}</ref> As of 2024, NASA lists 26,182 confirmed Mars-crossing asteroids.<ref name=jpello>{{cite web|title=Small-Body Database Query|url=https://ssd.jpl.nasa.gov/tools/sbdb_query.html#!|work=NASA|accessdate=3 June 2024|archive-date=27 September 2021|archive-url=https://web.archive.org/web/20210927184129/https://ssd.jpl.nasa.gov/tools/sbdb_query.html#!|url-status=live}}</ref>

====Asteroid belt====
The [[asteroid belt]] occupies a torus-shaped region between 2.3 and {{val|3.3|u=AU}} from the Sun, which lies between the orbits of Mars and Jupiter. It is thought to be remnants from the Solar System's formation that failed to coalesce because of the gravitational interference of Jupiter.<ref>{{Cite journal |last1=Petit |first1=J.-M. |last2=Morbidelli |first2=A. |last3=Chambers |first3=J. |date=2001 |title=The Primordial Excitation and Clearing of the Asteroid Belt |url=http://www.gps.caltech.edu/classes/ge133/reading/asteroids.pdf |url-status=dead |journal=[[Icarus (journal)|Icarus]] |volume=153 |issue=2 |pages=338–347 |bibcode=2001Icar..153..338P |doi=10.1006/icar.2001.6702 |archive-url=https://web.archive.org/web/20070221085835/http://www.gps.caltech.edu/classes/ge133/reading/asteroids.pdf |archive-date=21 February 2007 |access-date=22 March 2007}}</ref> The asteroid belt contains tens of thousands, possibly millions, of objects over one kilometer in diameter.<ref>{{Cite journal |last1=Tedesco |first1=Edward F. |last2=Cellino |first2=Alberto |last3=Zappalá |first3=Vincenzo |date=June 2005 |title=The Statistical Asteroid Model. I. The Main-Belt Population for Diameters Greater than 1 Kilometer |journal=The Astronomical Journal |language=en |volume=129 |issue=6 |pages=2869–2886 |bibcode=2005AJ....129.2869T |doi=10.1086/429734 |issn=0004-6256 |s2cid=119906696 |doi-access=free}}</ref> Despite this, the total mass of the asteroid belt is unlikely to be more than a thousandth of that of Earth.<ref name="Krasinsky2002">{{Cite journal |last1=Krasinsky |first1=G. A. |author-link=Georgij A. Krasinsky |last2=Pitjeva |first2=E. V. |author-link2=Elena V. Pitjeva |last3=Vasilyev |first3=M. V. |last4=Yagudina |first4=E. I. |date=July 2002 |title=Hidden Mass in the Asteroid Belt |journal=[[Icarus (journal)|Icarus]] |volume=158 |issue=1 |pages=98–105 |bibcode=2002Icar..158...98K |doi=10.1006/icar.2002.6837}}</ref> The asteroid belt is very sparsely populated; spacecraft routinely pass through without incident.<ref>{{Cite web |date=14 April 2000 |title=Cassini Passes Through Asteroid Belt |url=https://solarsystem.nasa.gov/news/12195/cassini-passes-through-asteroid-belt |url-status=live |archive-url=https://web.archive.org/web/20210125180703/https://solarsystem.nasa.gov/news/12195/cassini-passes-through-asteroid-belt |archive-date=25 January 2021 |access-date=1 March 2021 |website=NASA}}</ref>
[[File:The Four Largest Asteroids.jpg|thumb|The four largest asteroids: [[Ceres (dwarf planet)|Ceres]], [[4 Vesta|Vesta]], [[2 Pallas|Pallas]], [[10 Hygiea|Hygiea]]. Only Ceres and Vesta have been visited by a spacecraft and thus have a detailed picture.]]
Below are the descriptions of the three largest bodies in the asteroid belt. They are all considered to be relatively intact [[protoplanet]]s, a precursor stage before becoming a fully-formed planet (see [[List of exceptional asteroids]]):<ref>{{Cite journal |last1=McCord |first1=Thomas B. |last2=McFadden |first2=Lucy A. |last3=Russell |first3=Christopher T. |last4=Sotin |first4=Christophe |last5=Thomas |first5=Peter C. |date=7 March 2006 |title=Ceres, Vesta, and Pallas: Protoplanets, Not Asteroids |url=https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006EO100002 |url-status=live |journal=Eos |volume=87 |page=105 |bibcode=2006EOSTr..87..105M |doi=10.1029/2006EO100002 |archive-url=https://web.archive.org/web/20210928160233/https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006EO100002 |archive-date=28 September 2021 |access-date=12 September 2021 |number=10}}</ref><ref name="nasa-dawn20110329">{{cite web |author=Cook, Jia-Rui C. |date=29 March 2011 |title=When Is an Asteroid Not an Asteroid? |url=http://www.nasa.gov/mission_pages/dawn/news/dawn20110329.html |url-status=live |archive-url=https://web.archive.org/web/20110629163004/http://www.nasa.gov/mission_pages/dawn/news/dawn20110329.html |archive-date=29 June 2011 <!--DASHBot--> |access-date=30 July 2011 |publisher=NASA/JPL}}</ref><ref name="Marsset2020">{{Cite journal |last1=Marsset |first1=M. |last2=Brož |first2=M. |last3=Vernazza |first3=P. |last4=Drouard |first4=A. |display-authors=3 |date=2020 |title=The violent collisional history of aqueously evolved (2) Pallas |url=https://orbi.uliege.be/bitstream/2268/246670/1/Pallas_Marsset.pdf |journal=Nature Astronomy |volume=4 |issue=6 |pages=569–576 |bibcode=2020NatAs...4..569M |doi=10.1038/s41550-019-1007-5 |s2cid=212927521 |hdl-access=free |hdl=10261/237549 |access-date=4 January 2023 |archive-date=7 January 2023 |archive-url=https://web.archive.org/web/20230107085352/https://orbi.uliege.be/bitstream/2268/246670/1/Pallas_Marsset.pdf |url-status=live }}</ref>
* {{Visible anchor|Ceres|text=[[Ceres (dwarf planet)|Ceres]]}} (2.55–2.98&nbsp;AU) is the only dwarf planet in the asteroid belt.<ref name="IAU-QA">{{Cite web |title=Question and answers 2 |url=https://www.iau.org/public/themes/pluto/ |url-status=live |archive-url=https://web.archive.org/web/20160130022141/http://www.iau.org/public/themes/pluto/ |archive-date=30 January 2016 |access-date=31 January 2008 |publisher=IAU |quote=Ceres is (or now we can say it was) the largest asteroid{{spaces}}... There are many other asteroids that can come close to the orbital path of Ceres.}}</ref> It is the largest object in the belt, with a diameter of {{Convert|940|km|abbr=on}}.<ref name="Ermakov2017">{{cite journal |last1=Ermakov |first1=A. I. |last2=Fu |first2=R. R. |last3=Castillo-Rogez |first3=J. C. |last4=Raymond |first4=C. A. |last5=Park |first5=R. S. |last6=Preusker |first6=F. |last7=Russell |first7=C. T. |last8=Smith |first8=D. E. |last9=Zuber |first9=M. T. |date=November 2017 |title=Constraints on Ceres' Internal Structure and Evolution From Its Shape and Gravity Measured by the Dawn Spacecraft |journal=Journal of Geophysical Research: Planets |volume=122 |issue=11 |pages=2267–2293 |bibcode=2017JGRE..122.2267E |doi=10.1002/2017JE005302 |s2cid=133739176 |doi-access=free}}</ref> Its surface contains a mixture of [[carbon]],<ref name="Nature 12 2018">{{Cite journal |last1=Marchi |first1=S. |last2=Raponi |first2=A. |last3=Prettyman |first3=T. H. |last4=De Sanctis |first4=M. C. |last5=Castillo-Rogez |first5=J. |last6=Raymond |first6=C. A. |last7=Ammannito |first7=E. |last8=Bowling |first8=T. |last9=Ciarniello |first9=M. |last10=Kaplan |first10=H. |last11=Palomba |first11=E. |last12=Russell |first12=C. T. |last13=Vinogradoff |first13=V. |last14=Yamashita |first14=N. |year=2018 |title=An aqueously altered carbon-rich Ceres |journal=[[Nature Astronomy]] |volume=3 |issue=2 |pages=140–145 |doi=10.1038/s41550-018-0656-0 |s2cid=135013590}}</ref> frozen water and [[hydrate]]d minerals.<ref name="EPSC2">{{Cite book |last1=Raymond |first1=C. |title=European Planetary Science Congress |last2=Castillo-Rogez |first2=J. C. |last3=Park |first3=R. S. |last4=Ermakov |first4=A. |last5=Bland |first5=M. T. |last6=Marchi |first6=S. |last7=Prettyman |first7=T. |last8=Ammannito |first8=E. |last9=De Sanctis |first9=M. C. |date=September 2018 |volume=12 |chapter=Dawn Data Reveal Ceres' Complex Crustal Evolution |display-authors=4 |access-date=19 July 2020 |chapter-url=https://meetingorganizer.copernicus.org/EPSC2018/EPSC2018-645-1.pdf |archive-url=https://web.archive.org/web/20200130111631/https://meetingorganizer.copernicus.org/EPSC2018/EPSC2018-645-1.pdf |archive-date=30 January 2020 |url-status=live |author10=Russell, C.T.}}</ref> There are signs of past [[cryovolcano|cryovolcanic]] activity, where [[volatile (astrogeology)|volatile]] material such as water are erupted onto the surface, as seen in [[Bright spots on Ceres|surface bright spots]].<ref>{{cite web |last1=Krummheuer |first1=Birgit |date=6 March 2017 |title=Cryovolcanism on Dwarf Planet Ceres |url=http://www.mps.mpg.de/Cryovolcanism-on-Dwarf-Planet-Ceres |website=Max Planck Institute for Solar System Research |access-date=22 April 2024 |archive-date=2 February 2024 |archive-url=https://web.archive.org/web/20240202180118/https://www.mps.mpg.de/Cryovolcanism-on-Dwarf-Planet-Ceres |url-status=live }}</ref> Ceres has a very thin water vapor atmosphere, but practically speaking it is indistinguishable from a vacuum.<ref>{{Cite news |date=6 April 2017 |title=Confirmed: Ceres Has a Transient Atmosphere |url=https://www.universetoday.com/134922/confirmed-ceres-transient-atmosphere/ |url-status=live |archive-url=https://web.archive.org/web/20170415103956/https://www.universetoday.com/134922/confirmed-ceres-transient-atmosphere/ |archive-date=15 April 2017 |access-date=14 April 2017 |work=Universe Today |language=en}}</ref>
* {{Visible anchor|Pallas and Vesta|text=[[4 Vesta|Vesta]]}} (2.13–3.41&nbsp;AU) is the second-largest object in the asteroid belt.<ref name="Astronomy & Astrophysics">{{Cite report |url=https://meetingorganizer.copernicus.org/EPSC2022/EPSC2022-103.html |title=VLT/SPHERE imaging survey of D>100 km asteroids: Final results and synthesis |last1=Vernazza |first1=Pierre |last2=Ferrais |first2=Marin |date=6 July 2022 |publisher=Astronomy & Astrophysics |doi=10.5194/epsc2022-103 |page=A56 |last3=Jorda |first3=Laurent |last4=Hanus |first4=Josef |last5=Carry |first5=Benoit |last6=Marsset |first6=Michael |last7=Brož |first7=Miroslav |last8=Fetick |first8=Roman |last9=HARISSA team |doi-access=free |access-date=22 April 2024 |archive-date=22 April 2024 |archive-url=https://web.archive.org/web/20240422145344/https://meetingorganizer.copernicus.org/EPSC2022/EPSC2022-103.html |url-status=live }}</ref> Its fragments survive as the [[Vesta family|Vesta asteroid family]]<ref name="planetarysociety" /> and numerous [[HED meteorite]]s found on Earth.<ref name="Vestainterior">{{cite web |date=6 January 2011 |title=A look into Vesta's interior |url=https://www.mpg.de/877913/Vesta_asteroid |work=Max-Planck-Gesellschaft |access-date=22 April 2024 |archive-date=5 March 2023 |archive-url=https://web.archive.org/web/20230305200352/https://www.mpg.de/877913/Vesta_asteroid |url-status=live }}</ref> Vesta's surface, dominated by [[basalt]]ic and [[Metamorphic rock|metamorphic]] material, has a denser composition than Ceres's.<ref name="Takeda1997">{{cite journal |author=Takeda, H. |date=1997 |title=Mineralogical records of early planetary processes on the HED parent body with reference to Vesta |journal=Meteoritics & Planetary Science |volume=32 |issue=6 |pages=841–853 |bibcode=1997M&PS...32..841T |doi=10.1111/j.1945-5100.1997.tb01574.x |doi-access=free}}</ref> Its surface is marked by two giant craters: [[Rheasilvia]] and [[Veneneia (crater)|Veneneia]].<ref name="Schenk2012">{{cite journal |author=Schenk, P. |display-authors=etal |date=2012 |title=The Geologically Recent Giant Impact Basins at Vesta's South Pole |journal=Science |volume=336 |issue=6082 |pages=694–697 |bibcode=2012Sci...336..694S |doi=10.1126/science.1223272 |pmid=22582256 |s2cid=206541950}}</ref>
* [[2 Pallas|Pallas]] (2.15–2.57&nbsp;AU) is the third-largest object in the asteroid belt.<ref name="Astronomy & Astrophysics"/> It has its own [[Pallas family|Pallas]] [[Vesta family|asteroid family]].<ref name="planetarysociety">{{Cite web |last=Lakdawalla |first=Emily |author-link=Emily Lakdawalla |display-authors=etal |date=21 April 2020 |title=What Is A Planet? |url=https://www.planetary.org/worlds/what-is-a-planet |url-status=live |archive-url=https://web.archive.org/web/20220122142140/https://www.planetary.org/worlds/what-is-a-planet |archive-date=22 January 2022 |access-date=3 April 2022 |website=The Planetary Society}}</ref> Not much is known about Pallas because it has never been visited by a spacecraft,<ref>{{cite web |title=Athena: A SmallSat Mission to (2) Pallas |url=https://josephgorourke.com/research |url-status=dead |archive-url=https://web.archive.org/web/20211121181742/https://josephgorourke.com/research |archive-date=21 November 2021 |access-date=7 October 2020}}</ref> though its surface is predicted to be composed of silicates.<ref name="AutoCB-19">{{cite journal |author=Feierberg, M. A. |author2=Larson, H. P. |author3=Lebofsky, L. A. |date=1982 |title=The 3 Micron Spectrum of Asteroid 2 Pallas |journal=Bulletin of the American Astronomical Society |volume=14 |page=719 |bibcode=1982BAAS...14..719F}}</ref>

[[Hilda asteroid]]s are in a 3:2 resonance with Jupiter; that is, they go around the Sun three times for every two Jovian orbits.<ref name="Barucci">{{Cite book |last1=Barucci |first1=M. A. |title=Asteroids III |last2=Kruikshank |first2=D. P. |last3=Mottola |first3=S. |last4=Lazzarin |first4=M. |date=2002 |publisher=University of Arizona Press |location=Tucson, Arizona |pages=273–287 |chapter=Physical Properties of Trojan and Centaur Asteroids}}</ref> They lie in three linked clusters between Jupiter and the main asteroid belt.

[[Trojan (celestial body)|Trojan]]s are bodies located within another body's gravitationally stable [[Lagrangian point|Lagrange points]]: {{L4}}, 60° ahead in its orbit, or {{L5}}, 60° behind in its orbit.<ref name="spies">{{cite web |title=Trojan Asteroids |url=http://astronomy.swin.edu.au/cosmos/T/Trojan+Asteroids |url-status=live |archive-url=https://web.archive.org/web/20170623182748/http://astronomy.swin.edu.au/cosmos/T/Trojan+Asteroids |archive-date=23 June 2017 |access-date=13 June 2017 |website=Cosmos |publisher=Swinburne University of Technology}}</ref> Every planet except Mercury and Saturn is known to possess at least 1 trojan.<ref name="Connors">{{cite journal |last1= Connors|first1= Martin|last2= Wiegert|first2= Paul|last3= Veillet|first3= Christian|title= Earth's Trojan asteroid|date= 27 July 2011|journal= [[Nature (journal)|Nature]]|volume= 475|pages= 481–483|doi= 10.1038/nature10233|issue= 7357|bibcode= 2011Natur.475..481C|pmid= 21796207|s2cid= 205225571}}</ref><ref name=secondUranus>{{cite journal
|last2=de la Fuente Marcos |first2=Raúl
|last1=de la Fuente Marcos |first1=Carlos
|title=Asteroid 2014 YX<sub>49</sub>: a large transient Trojan of Uranus
|journal=Monthly Notices of the Royal Astronomical Society
|date=21 May 2017
|volume=467 |issue=2
|arxiv=1701.05541
|doi=10.1093/mnras/stx197 |pages=1561–1568|doi-access=free
|bibcode=2017MNRAS.467.1561D}}</ref><ref name=CeresVestatrojans>{{cite journal |first1=Apostolos A. |last1=Christou |first2=Paul |last2=Wiegert |title=A population of main belt asteroids co-orbiting with Ceres and Vesta |journal=Icarus |volume=217 |issue=1 |date=January 2012 |pages=27–42 |arxiv=1110.4810 |doi=10.1016/j.icarus.2011.10.016|bibcode=2012Icar..217...27C |s2cid=59474402 }}</ref> The [[Jupiter trojan]] population is roughly equal to that of the asteroid belt.<ref name="Yoshida2005">{{cite journal |last1=Yoshida |first1=Fumi |last2=Nakamura |first2=Tsuko |title=Size distribution of faint L4 Trojan asteroids |year=2005 |journal=The Astronomical Journal |volume=130 |issue=6 |pages=2900–11 |doi=10.1086/497571 |bibcode=2005AJ....130.2900Y|doi-access=free }}</ref> After Jupiter, Neptune possesses the most confirmed trojans, at 28.<ref>{{cite web |title=List of Neptune Trojans |work=Minor Planet Center |date=28 October 2018 |access-date=28 December 2018 |url=http://www.minorplanetcenter.org/iau/lists/NeptuneTrojans.html |archive-date=25 May 2012 |archive-url=https://archive.today/20120525133119/http://www.minorplanetcenter.org/iau/lists/NeptuneTrojans.html |url-status=live }}</ref>