Asteroïde: Verskil tussen weergawes

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k Robot: standardisering van verwysingsjablone en invoeging van argiefskakels. Ondersteun: shorturl.at/klqM2
k Robot: standardisering van verwysingsjablone en invoeging van argiefskakels. Ondersteun: shorturl.at/klqM2
Lyn 7:
Daar is miljoene asteroïdes, waarvan baie vermoedelik die oorblyfsels is van [[planetesimale]], liggame in die jong Son se [[sonnewel]] wat nooit groot genoeg geword het om [[planete]] te vorm nie.<ref>{{cite web |website=CNEOS |title=Frequently Asked Questions (FAQs) – What Are Asteroids And Comets? |url=http://neo.jpl.nasa.gov/faq/#ast |access-date=13 September 2010 |language=en |archive-url=https://web.archive.org/web/20170210085625/http://neo.jpl.nasa.gov/faq/ |archive-date=10 Februarie 2017 |url-status=live|df=dmy-all}}</ref> Die oorgrote meerderheid van bekende asteroïdes kom voor in die hoofasteroïdegordel tussen die wentelbane van [[Mars]] en Jupiter, of deel ’n wentelbaan met Jupiter (die [[Trojaan (sterrekunde)|Jupiter-trojane]]). Daar is egter taamlik groot families asteroïdes met ander wentelbane, insluitende die [[naby-aarde-voorwerp]]e. Individuele asteroïdes word geklassifiseer volgens hul kenmerkende [[Emissielyn|spektra]]. Die meeste val in drie hoofgroepe: C-, M- en S-tipe asteroïdes. Hulle is genoem na en word gewoonlik verbind met onderskeidelik [[koolstof]], [[metaal]] en [[silikaat]] (klipagtig). Asteroïdes se groottes wissel aansienlik; die grootste een, [[Ceres (dwergplaneet)|Ceres]], se deursnee is amper 1&nbsp;000&nbsp;km.
 
Asteroïdes verskil van komete en [[meteoroïde]]s. Die verskil tussen asteroïdes en komete is hul samestelling: Komete bestaan hoofsaaklik uit stof en ys en asteroïdes uit rots en minerale. Laasgenoemde het nader aan die Son ontstaan en bevat dus nie ys nie.<ref>{{cite web |title=What is the difference between an asteroid and a comet? |url=http://coolcosmos.ipac.caltech.edu/ask/181-What-is-the-difference-between-an-asteroid-and-a-comet- |website=Cool Cosmos |publisher=Infrared Processing and Analysis Center |access-date=13 Augustus 2016 |language=en |archive-url=https://web.archive.org/web/2019091021260820191019190907/http://coolcosmos.ipac.caltech.edu:80/ask/181-What-is-the-difference-between-an-asteroid-and-a-comet- |archive-date=1019 SeptemberOktober 2019 |url-status=live|df=dmy-all}}</ref> Die verskil tussen asteroïdes en meteoroïdes is hul grootte: Meteoroïdes het ’n deursnee van ’n meter of kleiner, terwyl asteroïdes se deursnee groter as ’n meter is.<ref name=Rubin2010>{{cite journal |last1=Rubin |first1=Alan E. |last2=Grossman |first2=Jeffrey N. |title=Meteorite and meteoroid: new comprehensive definitions |journal=Meteoritics and Planetary Science |date=Januarie 2010 |volume=45 |issue=1 |pages=114–122 |bibcode=2010M&PS...45..114R |doi=10.1111/j.1945-5100.2009.01009.x |doi-access=free}}</ref> Meteoroïdes kan dieselfde samestelling as óf asteroïdes óf komete hê.<ref name="Universe Today">{{cite web |title=What is the difference between asteroids and meteorites? |url=http://www.universetoday.com/36398/what-is-the-difference-between-asteroids-and-meteorites/ |website=Universe Today |last=Atkinson |first=Nancy |date=2 Junie 2015 |accessdate=13 Augustus 2016}}</ref>
 
Net een asteroïde, [[4 Vesta]], het ’n taamlik [[Albedo|weerkaatsende oppervlak]]. Dit is gewoonlik met die blote oog sigbaar, maar net as dit baie donker is en Vesta se posisie gunstig is. Net soms kan asteroïdes wat naby die Aarde verbybeweeg, vir ’n kort rukkie met die blote oog sigbaar wees.<ref>{{cite web |url=http://www.space.com/spacewatch/050204_2004_mn4.html |title=Closest Flyby of Large Asteroid to be Naked-Eye Visible |website=SPACE.com |first=Robert Roy |last=Britt |date=4 Februarie 2005 |language=en |archive-url=https://web.archive.org/web/20101209064401/http://www.space.com:80/spacewatch/050204_2004_mn4.html |archive-date=9 Desember 2010 |url-status=live|df=dmy-all}}</ref> In 2017 het die [[Kleinplaneetsentrum]] data oor byna 745&nbsp;000 voorwerpe in die binneste en buitenste Sonnestelsel gehad, met genoeg inligting oor
amper 504&nbsp;000 om ’n nommernaam te kry.<ref>{{cite web |url=http://minorplanetcenter.net/mpc/summary |title=Latest Published Data |access-date=11 Oktober 2017 |website=International Astronomical Union Minor Planet Center |language=en |archive-url=https://web.archive.org/web/2020041511431620200427214200/https://minorplanetcenter.net//mpc/summary |archive-date=1527 April 2020 |url-status=live|df=dmy-all}}</ref>
 
Die [[Verenigde Nasies]] het [[30 Junie]] as Internasionale Asteroïdedag verklaar om die publiek oor asteroïdes op te voed. Dié datum herdenk die [[Toengoeska-voorval|Toengoeska-asteroïde-impak]] op 30 Junie 1908 in [[Siberië]], [[Rusland]].<ref>{{cite press release |url=http://www.unoosa.org/oosa/en/informationfor/media/2016-unis-os-478.html |title=United Nations General Assembly proclaims 30 June as International Asteroid Day |date=7 Desember 2016 |id=UNIS/OS/478 |website=United Nations Office for Outer Space Affairs}}</ref><ref>{{cite web |url=https://www.un.org/ga/search/view_doc.asp?symbol=A/71/492 |others=Rapporteur: Awale Ali Kullane |title=International cooperation in the peaceful uses of outer space |date=25 Oktober 2016 |access-date=6 Desember 2016 |website=United Nations |language=en |archive-url=https://web.archive.org/web/20190102225331/http://www.un.org/ga/search/view_doc.asp?symbol=A/71/492 |archive-date=2 Januarie 2019 |url-status=live|df=dmy-all}}</ref>
 
In April 2018 het die B612 Foundation, wat hom onder meer toespits op verdediging teen asteroïdes, berig "die kans is 100&nbsp;persent dat ons deur ’n verwoestende asteroïde getref sal word, maar ons is nie 100&nbsp;persent seker wanneer nie".<ref name="DS-20180428">{{cite news |last=Harper |first=Paul |title=Earth will be hit by asteroid with 100% Certainty ...experts have warned it is "100pc certain" Earth will be devastated by an asteroid as millions are hurling towards the planet undetected |url=https://www.dailystar.co.uk/news/world-news/699177/Asteroids-earth-space-apocalypse-meteor-B612-Foundation |date=28 April 2018 |work=Daily Star |accessdate=26 November 2018 }}</ref><ref name="INQ-20180428">{{cite news |last=Homer |first=Aaron |title=Earth Will Be Hit By An Asteroid With 100 Percent Certainty, Says Space-Watching Group B612 – The group of scientists and former astronauts is devoted to defending the planet from a space apocalypse. |url=https://www.inquisitr.com/4881237/earth-will-be-hit-by-an-asteroid-with-100-percent-certainty-says-space-watching-group-b612/ |date=28 April 2018 |work=Inquisitr |access-date=26 November 2018 |language=en |archive-url=https://web.archive.org/web/20200124092654/https://www.inquisitr.com/4881237/earth-will-be-hit-by-an-asteroid-with-100-percent-certainty-says-space-watching-group-b612/ |archive-date=24 Januarie 2020 |url-status=live|df=dmy-all}}</ref> Ook die fisikus [[Stephen Hawking]] het in 2018 in sy laaste boek, ''Brief Answers to the Big Questions'', gemeen ’n asteroïdebotsing is die grootste bedreiging wat ons planeet in die gesig staar.<ref name="WP-20181015">{{cite news |last=Stanley-Becker |first=Isaac |title=Stephen Hawking feared race of ‘superhumans’ able to manipulate their own DNA |url=https://www.washingtonpost.com/news/morning-mix/wp/2018/10/15/stephen-hawking-feared-race-of-superhumans-able-to-manipulate-their-own-dna/ |date=15 Oktober 2018 |work=The Washington Post |accessdate=26 November 2018 }}</ref><ref name="QZ-20181014">{{cite web |last=Haldevang |first=Max de |title=Stephen Hawking left us bold predictions on AI, superhumans, and aliens |url=https://qz.com/1423685/stephen-hawking-says-superhumans-will-take-over-ai-is-a-threat-and-humans-will-conquer-space/ |date=14 Oktober 2018 |work=Quartz |access-date=26 November 2018 |language=en |archive-url=https://web.archive.org/web/20200304115756/https://qz.com/1423685/stephen-hawking-says-superhumans-will-take-over-ai-is-a-threat-and-humans-will-conquer-space/ |archive-date=4 Maart 2020 |url-status=live|df=dmy-all}}</ref><ref name="NYT-20180618">{{cite news |last=Bogdan |first=Dennis |title=\Better Way To Avoid Devastating Asteroids Needed? |url=https://www.nytimes.com/2018/06/14/science/asteroids-nasa-nathan-myhrvold.html#permid=27500228:27506217 |date=18 Junie 2018 |work=The New York Times |access-date=26 November 2018 |language=en |archive-url=https://web.archive.org/web/2020030620125720200423070930/https://www.nytimes.com/2018/06/14/science/asteroids-nasa-nathan-myhrvold.html |archive-date=623 MaartApril 2020 |url-status=live|df=dmy-all}}</ref>
 
In Junie 2018 het die [[VSA]] se nasionale wetenskap-en-tegnologieraad gewaarsku dat Amerika onvoorbereid op ’n asteroïde-impak is. Die raad het die "[https://www.whitehouse.gov/wp-content/uploads/2018/06/National-Near-Earth-Object-Preparedness-Strategy-and-Action-Plan-23-pages-1MB.pdf National Near-Earth Object Preparedness Strategy Action Plan]" ontwikkel en uitgereik om beter daarop voor te berei.<ref name="WH-20180621">{{cite web |author=Staff |title=National Near-Earth Object Preparedness Strategy Action Plan |url=https://www.whitehouse.gov/wp-content/uploads/2018/06/National-Near-Earth-Object-Preparedness-Strategy-and-Action-Plan-23-pages-1MB.pdf |format=PDF |date=21 June 2018 |work=White House |accessdate=22 June 2018 }}</ref><ref name="GIZ-20180621">{{cite news |last=Mandelbaum |first=Ryan F. |title=America Isn't Ready to Handle a Catastrophic Asteroid Impact, New Report Warns |url=https://gizmodo.com/america-isnt-ready-to-handle-a-catastrophic-asteroid-im-1827014709 |date=21 Junie 2018 |work=Gizmodo |access-date=22 Junie 2018 |language=en |archive-url=https://web.archive.org/web/20191106085535/https://gizmodo.com/america-isnt-ready-to-handle-a-catastrophic-asteroid-im-1827014709 |archive-date=6 November 2019 |url-status=live|df=dmy-all}}</ref><ref name="ICARUS-220180522">{{cite journal |last=Myhrvold |first=Nathan |authorlink=Nathan Myhrvold |title=An empirical examination of WISE/NEOWISE asteroid analysis and results |url=https://www.sciencedirect.com/science/article/pii/S0019103516307643 |date=22 Mei 2018 |journal=Icarus|volume=314 |pages=64–97 |doi=10.1016/j.icarus.2018.05.004 |accessdate=22 June 2018 |bibcode=2018Icar..314...64M }}</ref><ref name="NYT-20180618" /><ref name="NYT-20180614">{{cite news |last=Chang |first=Kenneth |title=Asteroids and Adversaries: Challenging What NASA Knows About Space Rocks |quote=Two years ago, NASA dismissed and mocked an amateur’s criticisms of its asteroids database. Now Nathan Myhrvold is back, and his papers have passed peer review. |url=https://www.nytimes.com/2018/06/14/science/asteroids-nasa-nathan-myhrvold.html |date=14 Junie 2018 |work=The New York Times |access-date=26 November 2018 |language=en |archive-url=https://web.archive.org/web/2020030620125720200423070930/https://www.nytimes.com/2018/06/14/science/asteroids-nasa-nathan-myhrvold.html |archive-date=623 MaartApril 2020 |url-status=live|df=dmy-all}}</ref> Volgens kennersgetuienis in 2013 in die Amerikaanse kongres het [[Nasa]] minstens vyf jaar van voorbereiding nodig voordat ’n sending van stapel gestuur kan word om ’n asteroïde te onderskep.<ref name="US-Congress-20130410">{{cite web |author=U.S.Congress |title=Threats From Space: a Review of U.S. Government Efforts to Track and mitigate Asteroids and Meteors (Part I and Part II) – Hearing Before the Committee on Science, Space, and Technology House of Representatives One Hundred Thirteenth Congress First Session |url=http://www.gpo.gov/fdsys/pkg/CHRG-113hhrg80552/pdf/CHRG-113hhrg80552.pdf |date=19 Maart 2013 |page=147 |work=United States Congress |accessdate=26 November 2018 }}</ref>
 
== Ontdekking ==
Lyn 26:
Ander, soortgelyke liggame is ná Ceres ontdek. Hulle het, nes sterre, soos ligpunte gelyk deur die ou instrumente van destyds. Hulle het geen [[protoplanetêre skyf|protoplanetêre skywe]] gehad nie en is verder van sterre onderskei deur hul skynbare beweging. Dit het die sterrekundige [[William Herschel]] aangespoor om hulle "asteroïdes" te noem.<ref>{{cite web |title=HAD Meeting with DPS, Denver, October 2013 – Abstracts of Papers |url=http://had.aas.org/meetings/2013bAbstracts.html#HADII |access-date=14 Oktober 2013 |language=en |archive-url=https://web.archive.org/web/20160601202151/https://had.aas.org/meetings/2013bAbstracts.html |archive-date=1 Junie 2016 |url-status=dead|df=dmy-all}}</ref> Volgens Clifford Cunningham is die term uitgedink deur Charles Burney jr., die seun van ’n vriend van Herschel.<ref>{{cite news |first=Robert |last=Nolin |title=Local expert reveals who really coined the word 'asteroid' |url=http://www.sun-sentinel.com/news/broward/fl-asteroid-word-origin-20131008,0,501498,full.story |date=8 October 2013 |access-date=10 October 2013 |newspaper=SunSentinel}}</ref><ref>{{cite web |url=http://www.space.com/10593-post-william-herschel-coin-term-asteroid.html |title=Who Really Invented the Word 'Asteroid' for Space Rocks? |last=Wall |first=Mike |website=space.com |date=10 Januarie 2011 |access-date=10 Oktober 2013 |language=en |archive-url=https://web.archive.org/web/20200228233918/https://www.space.com/10593-post-william-herschel-coin-term-asteroid.html |archive-date=28 Februarie 2020 |url-status=live|df=dmy-all}}</ref> In [[Grieks]] is dit ἀστεροειδής, of ''asteroeidēs'', wat beteken "steragtig" of "stervorming". Dit is afgelei van die Antieke Griekse woord ἀστήρ ''astēr'', "ster" of "planeet". In die vroeë tweede helfte van die 19de eeu is die terme "asteroïde" en "planeet" (nie altyd as "kleinplaneet" uitgesonder nie) afwisselend gebruik.
 
Hier is ’n oorsig van die ontdekkingsgeskiedenis van asteroïdes:<ref name=Astronoo>{{cite web |url=http://www.astronoo.com/en/articles/asteroids-list.html |title=List of asteroids classified by size — Astronoo |last=Simoes |first=Christian |website=www.astronoo.com |access-date=7 November 2018 |language=en |archive-url=https://web.archive.org/web/2020031502110520191019060340/http://www.astronoo.com:80/en/articles/asteroids-list.html |archive-date=1519 MaartOktober 20202019 |url-status=live|df=dmy-all}}</ref>
* 10 teen 1849
** [[1 Ceres]] [[1801]]
Lyn 77:
Twee gebeure in latere dekades het die kommer laat toeneem: die algemene aanvaarding dat ’n impak die [[Kryt-Paleogeen-uitwissing]] veroorsaak het, en die waarneming in 1994 van die komeet [[Shoemaker-Levy 9]] wat teen Jupiter bots. Die Amerikaanse weermag het ook inligting gedeklassifiseer dat sy militêre satelliete, wat gebou is om [[Kernwapen|kernontploffings]] op te spoor, honderde botsings in die boonste [[atmosfeer]] waargeneem het deur voorwerpe met ’n deursnee wat wissel van een tot 10&nbsp;meter.
 
Al hierdie oorwegings het help lei tot hoogs doeltreffende opnames wat bestaan uit [[kamera]]s en [[rekenaar]]s wat die beweging van [[elektriese lading]]s kan waarneem en direk aan teleskope verbind is. In 2011 is geraam dat 89% tot 96% van die naby-aarde-asteroïdes met ’n deursnee van ’n kilometer of meer al ontdek is.<ref name="nasa_neo" /> Instrumente wat sulke stelsels gebruik, sluit in:<ref>{{cite web |last=Yeomans |first=Don |url=http://neo.jpl.nasa.gov/programs/ |title=Near Earth Object Search Programs |publisher=NASA |access-date=15 April 2008 |language=en |archive-url=https://web.archive.org/web/20170210073632/http://neo.jpl.nasa.gov/programs/ |archive-date=10 Februarie 2017 |url-status=live|df=dmy-all}}</ref>
<ref>{{cite web |url=https://cneos.jpl.nasa.gov/stats/site_all.html |title=Discovery Statistics – by Survey (all) |publisher=NASA |access-date=27 Desember 2018 |date=27 Desember 2018 |language=en |archive-url=https://web.archive.org/web/20191015142804/https://cneos.jpl.nasa.gov/stats/site_all.html |archive-date=15 Oktober 2019 |url-status=live|df=dmy-all}}</ref>
| last=Yeomans | first=Don
| url=http://neo.jpl.nasa.gov/programs/
| title=Near Earth Object Search Programs
| publisher=NASA | accessdate=15 April 2008 | archiveurl= https://web.archive.org/web/20080424093951/http://neo.jpl.nasa.gov/programs/| archivedate= 24 April 2008 <!--DASHBot-->|url-status=live}}</ref>
<ref>{{cite web
| url=https://cneos.jpl.nasa.gov/stats/site_all.html
| title=Discovery Statistics – by Survey (all)
| publisher=NASA
| access-date=27 Desember 2018
| date=27 Desember 2018
| archive-url=https://web.archive.org/web/20181228041653/https://cneos.jpl.nasa.gov/stats/site_all.html
| archive-date=28 Desember 2018
|url-status=live}}</ref>
* Lincoln Near-Earth Asteroid Research (LINEAR)
* Near-Earth Asteroid Tracking (NEAT)
Line 122 ⟶ 110:
Toe asteroïdes aanvanklik ontdek is, is hulle beskou as ’n ander klas voorwerpe as komete. Daar was dus geen sambreelterm vir die twee soorte liggame nie, totdat die term "klein Sonnestelselliggaam" in 2006 geskep is. Die grootste verskil tussen asteroïdes en komete is dat ’n komeet ’n [[koma]] het as gevolg van die [[sublimasie]] van yse naby die oppervlak vanweë die Son se straling. ’n Paar voorwerpe is al as albei geklassifiseer omdat hulle eers as kleinplanete beskou is, maar later tekens van komeetaktiwiteit getoon het. Net so raak sommige komete (dalk almal) se vlugtige yse eindelik op en word hulle asteroïde-agtig. Nog ’n onderskeid is dat komete gewoonlik [[Eksentrisiteit (sterrekunde)|eksentrieker wentelbane]] as die meeste asteroïdes het; die meeste asteroïdes met merkbaar eksentrieke wentelbane is moontlik rustende of uitgewerkte komete.<ref>{{cite web|authors=Weissman, Paul R.; Bottke, William F. Jr.; Levinson, Harold F. |title=Evolution of Comets into Asteroids |website=Southwest Research Institute, Planetary Science Directorate |date=2002 |url=http://www.boulder.swri.edu/~hal/PDF/asteroids3.pdf |accessdate= 3 Augustus 2010}}</ref>
 
Byna twee eeue lank – van die ontdekking van Ceres in 1801 tot met die ontdekking van die eerste [[Sentour (kleinplaneet)|sentour]], [[2060 Chiron|Chiron]], in 1977 – het alle bekende asteroïdes vir die grootste deel van hul wentelbaan by of binne die wentelbaan van Jupiter gebly, hoewel party soos [[944 Hidalgo|Hidalgo]] soms ver van Jupiter af beweeg het. Dié tussen Mars en Jupiter se wentelbane was jare lank bloot as "die asteroïdes" bekend.<ref>{{cite news |url=https://trove.nla.gov.au/newspaper/page/2368062 |title=The Asteroids |newspaper=The Queenslander |access-date=25 Junie 2018 |date=16 Junie 1932 |author=D. en A.C. Eglinton |department=Astronomy (rubriek) |language=en |archive-url=https://web.archive.org/web/20180625161058/https://trove.nla.gov.au/newspaper/page/2368062 |archive-date=25 Junie 2018 |url-status=live|df=dmy-all}}</ref> Toe sterrekundiges meer klein liggame begin vind wat permanent anderkant Jupiter bly, dit wat nou sentoure genoem word, het hulle dit as tradisionele asteroïdes beskou, hoewel gedebatteer is oor of hulle as asteroïdes beskou moet word of as ’n nuwe soort voorwerp. Toe die eerste [[trans-Neptunus-voorwerp]] (buiten [[Pluto]]), [[15760 Albion|Albion]], in 1992 ontdek word en veral toe groot getalle soortgelyke voorwerpe gevind word, is nuwe terme uitgedink om die vraagstuk te ontduik: [[Kuipergordel]]voorwerp, trans-Neptunus-voorwerp, [[Verstrooide skyf|verstrooideskyfvoorwerp]], ens. Hulle kom in die koue buitewyke van die Sonnestelsel voor waar yse [[Vaste stof|vaste stowwe]] bly en komeetagtige voorwerpe nie na verwagting veel komeetaktiwiteit toon nie; as sentoure of trans-Neptunus-voorwerpe naby die Son kom, sal hul vlugtige yse sublimeer. Hulle sal dan volgens tradisie as komete geklassifiseer word en nie as asteroïdes nie.
|title=The Asteroids
|newspaper=The Queenslander
|accessdate = 25 Junie 2018
|date=16 Junie 1932
|author=D. en A.C. Eglinton
|department=Astronomy (rubriek)}}</ref> Toe sterrekundiges meer klein liggame begin vind wat permanent anderkant Jupiter bly, dit wat nou sentoure genoem word, het hulle dit as tradisionele asteroïdes beskou, hoewel gedebatteer is oor of hulle as asteroïdes beskou moet word of as ’n nuwe soort voorwerp. Toe die eerste [[trans-Neptunus-voorwerp]] (buiten [[Pluto]]), [[15760 Albion|Albion]], in 1992 ontdek word en veral toe groot getalle soortgelyke voorwerpe gevind word, is nuwe terme uitgedink om die vraagstuk te ontduik: [[Kuipergordel]]voorwerp, trans-Neptunus-voorwerp, [[Verstrooide skyf|verstrooideskyfvoorwerp]], ens. Hulle kom in die koue buitewyke van die Sonnestelsel voor waar yse [[Vaste stof|vaste stowwe]] bly en komeetagtige voorwerpe nie na verwagting veel komeetaktiwiteit toon nie; as sentoure of trans-Neptunus-voorwerpe naby die Son kom, sal hul vlugtige yse sublimeer. Hulle sal dan volgens tradisie as komete geklassifiseer word en nie as asteroïdes nie.
 
Die naaste van dié voorwerpe aan die binneste Sonnestelsel is die Kuipergordelvoorwerpe – hulle word "voorwerpe" genoem deels om ’n klassifikasie as óf komete óf asteroïdes te voorkom.<ref name=KBOasteroids>{{cite news |url=http://curious.astro.cornell.edu/question.php?number=601 |title=Are Kuiper Belt Objects asteroids? |work=Ask an astronomer |publisher=Cornell University |language=en |archive-url=https://web.archive.org/web/2020031300283320200418201152/http://curious.astro.cornell.edu/question.php?number=601 |archive-date=1318 MaartApril 2020 |url-status=live|df=dmy-all}}</ref> Hul samestelling is vermoedelik hoofsaaklik komeetagtig, hoewel sommige meer soos asteroïdes kan wees.<ref>{{cite web |url=http://rst.gsfc.nasa.gov/Sect19/Sect19_22.html |author=Nicholas M. Short, Sr. |title=Asteroids and Comets |website=NASA.gov |url-status=dead |archiveurl=https://web.archive.org/web/20080925014037/http://rst.gsfc.nasa.gov///Sect19/Sect19_22.html|archivedate=25 September 2008}}</ref> Verder het die meeste nie die hoogs eksentrieke wentelbane wat met komete verbind word nie, en dié wat tot dusver ontdek is, is groter as tradisionele komeetkerns. (Die heelwat verder geleë [[Oortwolk]] is hipoteties die hoofbron van sluimerende komete.) Ander onlangse waarnemings, soos die ontleding van komeetstof wat deur die Stardust-sondeerder versamel is, laat toenemend die onderskeid tussen komete en asteroïdes vervaag.<ref>{{cite news |url=http://www.sciam.com/podcast/episode.cfm?id=ADD0878B-D6C3-3B70-7B5BC373545BB82D |title=Comet Dust Seems More Asteroidy |work=Scientific American |date=25 Januarie 2008 |language=en |archive-url=https://web.archive.org/web/20090211233859/http://www.sciam.com:80/podcast/episode.cfm?id=ADD0878B-D6C3-3B70-7B5BC373545BB82D |archive-date=11 Februarie 2009 |url-status=live|df=dmy-all}}</ref> Dit dui op ’n "onafgebrokenheid tussen asteroïdes en komete", eerder as ’n skerp skeidskyn.<ref>{{cite news |url=https://www.newscientist.com/channel/solar-system/comets-asteroids/dn13224-comet-samples-are-surprisingly-asteroidlike.html |title=Comet samples are surprisingly asteroid-like |work=New Scientist |date=24 Januarie 2008}}</ref>
 
Die kleinplanete anderkant Jupiter se wentelbaan word soms "asteroïdes" genoem. Die term word egter al hoe meer beperk tot kleinplanete in die binneste Sonnestelsel.<ref name="KBOasteroids" /> In hierdie artikel word die woord se betekenis dus merendeels beperk tot die klassieke asteroïdes: voorwerpe in die [[asteroïdegordel]], [[Trojaan (sterrekunde)|Jupiter-trojane]] en [[naby-aarde-voorwerp]]e.
Line 212 ⟶ 194:
| doi=10.1016/S0019-1035(03)00146-5 |display-authors=3}}</ref> Sy samestelling is soortgelyk aan dié van Ceres: baie [[koolstof]] en [[silikon]] en dalk gedeeltelik gedifferensieerd.<ref>{{cite journal |title=The composition of asteroid 2 Pallas and its relation to primitive meteorites |author=Larson, H.P. |author2=Feierberg, M.A. |author3=Lebofsky, L.A. |last-author-amp=yes |date=1983 |bibcode=1983Icar...56..398L |volume=56 |issue=3 |page=398 |journal=Icarus |doi=10.1016/0019-1035(83)90161-6}}</ref> Pallas is die hoofvoorwerp van die Pallas-familie asteroïdes.
 
Hygiea is die koolstofrykste asteroïde<ref>{{cite journal |title=10 Hygiea: ISO Infrared Observations |journal=Icarus |volume=156 |issue=1 |pages=202 |author=Barucci, M.A. |url=http://www.lesia.obspm.fr/~crovisier/biblio/preprint/bar02_icarus.pdf |format=PDF |date=2002 |accessdate=21 Oktober 2007 |archiveurl=https://web.archive.org/web/20071128200223/http://www.lesia.obspm.fr/~crovisier/biblio/preprint/bar02_icarus.pdf |archivedate=28 November 2007 |url-status=dead |display-authors=etal |df=dmy-all|bibcode=2002Icar..156..202B |doi=10.1006/icar.2001.6775 }}</ref> en lê, anders as die ander groot asteroïdes, relatief naby aan die [[sonnebaan]].<ref>{{cite web |title=Ceres the Planet |work=orbitsimulator.com |url=http://www.orbitsimulator.com/gravity/articles/ceres.html |access-date=20 Oktober 2007 |language=en |archive-url=https://web.archive.org/web/2018093003510320180929054549/http://www.orbitsimulator.com/gravity/articles/ceres.html |archive-date=3029 September 2018 |url-status=live|df=dmy-all}}</ref> Dit is die grootste lid en vermoedelik die hoofvoorwerp van die Hygiea-familie asteroïdes.
 
{| class="wikitable"
Line 327 ⟶ 309:
Die fisiese samestelling van asteroïdes varieer en word nie goed verstaan nie. Dit lyk of Ceres saamgestel is uit ’n rotsagtige kern wat met ’n ysmantel bedek is, terwyl Vesta vermoedelik ’n [[nikkel]]-[[yster]]kern, [[olivien]]mantel en [[Lawa|basaltkors]] het.<ref>{{cite web |url=http://hubblesite.org/newscenter/archive/releases/1995/20/image/ |publisher=HubbleSite – NewsCenter |title=Asteroid or Mini-Planet? Hubble Maps the Ancient Surface of Vesta – Release Images |date=19 April 1995 |access-date=27 Januarie 2015 |language=en |archive-url=https://web.archive.org/web/20160706164950/http://hubblesite.org/newscenter/archive/releases/1995/20/image/ |archive-date=6 Julie 2016 |url-status=live|df=dmy-all}}</ref> Hygiea, wat lyk of dit ’n primitiewe samestelling van koolstofagtige [[chondriet]] het, is vermoedelik die grootste ongedifferensieerde asteroïde. Die meeste kleiner asteroïdes is vermoedelik rommelhope wat losweg deur swaartekrag bymekaargehou word, hoewel die grootstes waarskynlik solied is. Sommige asteroïdes het mane of is deel van ’n dubbelvoorwerp: Rommelhope, mane, dubbelasteroïdes en verspreide asteroïdefamilies is vermoedelik die gevolg van botsings wat ’n moederasteroïde of moontlik ’n planeet verwoes het.<ref name="ARX-20060816">{{cite journal |last=Soter |first=Steven |title=What is a Planet? |url=https://arxiv.org/ftp/astro-ph/papers/0608/0608359.pdf |date=16 Augustus 2006 |format=PDF |accessdate=25 Desember 2017 }}</ref>
 
Asteroïdes bevat spore van [[Aminosuur|aminosure]] en ander organiese samestellings, en sommige geleerdes vermoed asteroïdebotsings kon die vroeë aarde voorsien het van die [[Chemikalie|chemikalieë]] wat nodig is om lewe te skep, of het dalk self lewe na die Aarde gebring.<ref>{{cite web |url=http://www.space.com/scienceastronomy/planetearth/meteor_sugar_011219.html |title=Life is Sweet: Sugar-Packing Asteroids May Have Seeded Life on Earth |website=SPACE.com |date=19 Desember 2001 |language=en |archive-url=https://web.archive.org/web/20100812010941/http://www.space.com:80/scienceastronomy/planetearth/meteor_sugar_011219.html |archive-date=12 Augustus 2010 |url-status=dead|df=dmy-all}}</ref> In Augustus 2011 is ’n verslag gepubliseer wat geskoei is op [[Nasa]]-studies van meteoriete wat op Aarde gevind is, en daarin is voorgestel [[DNS]]- en [[RNS]]-komponente ([[adenien]], [[guanien]] en verwante [[Organiese verbinding|organiese molekules]]) kon in die buitenste ruim op asteroïdes en komete gevorm gewees het.<ref name="Callahan">{{cite journal |display-authors=3 |last1=Callahan |first1=M.P. |last2=Smith |first2=K.E. |last3=Cleaves |first3=H.J. |last4=Ruzica |first4=J. |last5=Stern |first5=J.C. |last6=Glavin |first6=D.P. |last7=House |first7=C.H. |last8=Dworkin |first8=J.P. |date=11 Augustus 2011 |title=Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases |journal=PNAS |doi=10.1073/pnas.1106493108 |doi-access=free |pmid=21836052 |pmc=3161613 |volume=108 |issue=34 |pages=13995–13998|bibcode = 2011PNAS..10813995C }}</ref><ref name="Steigerwald">{{cite web |last=Steigerwald |first=John |title=NASA Researchers: DNA Building Blocks Can Be Made in Space |url=http://www.nasa.gov/topics/solarsystem/features/dna-meteorites.html |publisher=NASA |date=8 Augustus 2011 |access-date=10 Augustus 2011 |language=en |archive-url=https://web.archive.org/web/2020041002454120200426055700/https://www.nasa.gov/topics/solarsystem/features/dna-meteorites.html |archive-date=1026 April 2020 |url-status=livedead|df=dmy-all}}</ref><ref name="DNA">{{cite web |author=ScienceDaily Staff |title=DNA Building Blocks Can Be Made in Space, NASA Evidence Suggests |url=https://www.sciencedaily.com/releases/2011/08/110808220659.htm |date=9 Augustus 2011 |publisher=ScienceDaily |accessdate=9 Augustus 2011}}</ref>
 
[[Lêer:PIA18469-AsteroidCollision-NearStarNGC2547-ID8-2013.jpg|duimnael|240px|Die vorming van planete deur asteroïdebotsings (kunstenaar se voorstelling).]]
Line 338 ⟶ 320:
| title=Ice confirmed on an asteroid
| publisher=Science News | url=http://www.sciencenews.org/view/generic/id/48174/title/Ice_confirmed_on_an_asteroid
| accessdate=9 Oktober 2009 | archiveurl= https://web.archive.org/web/2009101105104020091012075224/http://www.sciencenews.org/view/generic/id/48174/title/Ice_confirmed_on_an_asteroid| archivedate= 12 Oktober 2009 <!--DASHBot-->|url-status=live}}</ref><ref>{{cite web |last=Atkinson |first=Nancy |date=8 Oktober 2009 |title=More water out there, ice found on an asteroid |work=International Space Fellowship |access-date=11 Oktober 2009 |url=http://spacefellowship.com/2009/10/08/more-water-out-there-ice-found-on-an-asteroid/ | archivedatearchive-url= 11 Oktober https://web.archive.org/web/20091212144142/http://spacefellowship.com:80/2009 <!/10/08/more-water-DASHBotout-there->ice-found-on-an-asteroid/ |archive-date=12 Desember 2009 |url-status=live|df=dmy-all}}</ref><ref name="Campins2010">{{ Cite journal |display-authors=3 |author1=Campins, H. |author2=Hargrove, K |author3=Pinilla-Alonso, N |author4=Howell, E.S. |author5=Kelley, M.S. |author6=Licandro, J. |author7=Mothé-Diniz, T. |author8=Fernández, Y. |author9=Ziffer, J. |title=Water ice and organics on the surface of the asteroid 24 Themis |journal=Nature |volume=464 |issue=7293 |date=2010 |doi=10.1038/nature09029 |pmid=20428164 |pages=1320–1321 |bibcode= 2010Natur.464.1320C}}</ref><ref>{{Cite journal |last=Rivkin |first=Andrew S. |last2=Emery |first2=Joshua P. |title=Detection of ice and organics on an asteroidal surface |journal=Nature |volume=464 |issue=7293 |pages=1322–1323 |date=2010 |doi=10.1038/nature09028 |pmid=20428165 |bibcode= 2010Natur.464.1322R}}</ref> Wetenskaplikes meen dit is moontlik dat van die eerste water op Aarde hierheen gebring is deur asteroïdebotsings ná die botsing wat die Maan gevorm het. Die teenwoordigheid van ys op Themis steun dié teorie.<ref name="Campins2010" />
| accessdate=9 Oktober 2009 | archiveurl= https://web.archive.org/web/20091012075224/http://www.sciencenews.org/view/generic/id/48174/title/Ice_confirmed_on_an_asteroid| archivedate= 12 Oktober 2009 <!--DASHBot-->|url-status=live}}</ref><ref>{{cite web
| last = Atkinson
| first = Nancy
| date = 8 Oktober 2009
| title = More water out there, ice found on an asteroid
| work = International Space Fellowship
| accessdate = 11 Oktober 2009
| url = http://spacefellowship.com/2009/10/08/more-water-out-there-ice-found-on-an-asteroid/
| archiveurl= https://web.archive.org/web/20091011051040/http://spacefellowship.com/2009/10/08/more-water-out-there-ice-found-on-an-asteroid/| archivedate= 11 Oktober 2009 <!--DASHBot-->|url-status=live}}</ref><ref name="Campins2010">{{ Cite journal |display-authors=3 |author1=Campins, H. |author2=Hargrove, K |author3=Pinilla-Alonso, N |author4=Howell, E.S. |author5=Kelley, M.S. |author6=Licandro, J. |author7=Mothé-Diniz, T. |author8=Fernández, Y. |author9=Ziffer, J. |title=Water ice and organics on the surface of the asteroid 24 Themis |journal=Nature |volume=464 |issue=7293 |date=2010 |doi=10.1038/nature09029 |pmid=20428164 |pages=1320–1321 |bibcode= 2010Natur.464.1320C}}</ref><ref>{{Cite journal |last=Rivkin |first=Andrew S. |last2=Emery |first2=Joshua P. |title=Detection of ice and organics on an asteroidal surface |journal=Nature |volume=464 |issue=7293 |pages=1322–1323 |date=2010 |doi=10.1038/nature09028 |pmid=20428165 |bibcode= 2010Natur.464.1322R}}</ref> Wetenskaplikes meen dit is moontlik dat van die eerste water op Aarde hierheen gebring is deur asteroïdebotsings ná die botsing wat die Maan gevorm het. Die teenwoordigheid van ys op Themis steun dié teorie.<ref name="Campins2010" />
 
In Oktober 2013 is water vir die eerste keer op ’n ekstrasolêre liggaam waargeneem – op ’n asteroïde wat om die [[witdwerg]] [[GD 61]] wentel.<ref>{{cite web |last=Mack |first=Eric |title=Newly spotted wet asteroids point to far-flung Earth-like planets |url=http://news.cnet.com/8301-17938_105-57607077-1/newly-spotted-wet-asteroids-point-to-far-flung-earth-like-planets/ |publisher=CNET |language=en |archive-url=https://web.archive.org/web/20131028145725/http://news.cnet.com/8301-17938_105-57607077-1/newly-spotted-wet-asteroids-point-to-far-flung-earth-like-planets/ |archive-date=28 Oktober 2013 |url-status=live|df=dmy-all}}</ref> Op 22 Januarie 2014 het wetenskaplikes van die [[Europese Ruimteagentskap]] (ESA) verslag gedoen oor die eerste besliste waarneming van [[waterdamp]] op die dwergplaneet Ceres in die asteroïdegordel.<ref name="KüppersO’Rourke2014">{{cite journal |display-authors=3 |last1=Küppers |first1=Michael |last2=O’Rourke |first2=Laurence |last3=Bockelée-Morvan |first3=Dominique |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 |date=2014 |pages=525–527 |doi=10.1038/nature12918 |bibcode = 2014Natur.505..525K |pmid=24451541}}</ref> Die waarneming is gedoen met die [[infrarooi]]geriewe van die [[Herschel-ruimtesterrewag]].<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 Januarie 2014 |work=NASA |access-date=22 Januarie 2014 |language=en |archive-url=https://web.archive.org/web/20190926062100/https://www.nasa.gov/press/2014/january/herschel-telescope-detects-water-on-dwarf-planet/ |archive-date=26 September 2019 |url-status=live|df=dmy-all}}</ref> Dié bevinding was onverwags omdat komete, en nie asteroïdes nie, gewoonlik met "spuitstrale en pluime" verbind word. Volgens een van die wetenskaplikes "vervaag die verskille tussen komete en asteroïdes al hoe meer".<ref name="NASA-20140122" />
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Die meeste asteroïdes buiten die vier grootstes (Ceres, Pallas, Vesta en Hygiea) lyk waarskynlik dieselfde, hoewel hul vorms onreëlmatig is. Mathilde (deursnee: 50&nbsp;km) is ’n rommelhoop vol kraters wat net so breed is as die asteroïde se [[radius]], en aardgebaseerde waarnemings van Davida (300&nbsp;km), een van die grootstes naas die grootste vier, onthul ’n soortgelyke hoekige profiel, wat daarop dui dat dit ook vol radiusgrootte-kraters is.<ref>{{cite journal |display-authors=3 |first1=A.R. |last1=Conrad |first2=C. |last2=Dumas |first3=W.J. |last3=Merline |first4=J.D. |last4=Drummonf |first5=R.D. |last5=Campbell |first6=R.W. |last6=Goodrich |first7=D. |last7=Le Mignant |first8=F.H. |last8=Chaffee |first9=T. |last9=Fusco |first10=S.H. |last10=Kwok |first11=R.I. |last11=Knight |date=2007 |journal=Icarus |volume=191 |issue=2 |pages=616–627 |doi=10.1016/j.icarus.2007.05.004 |url=http://www2.keck.hawaii.edu/inst/people/conrad/research/pub/d511.pdf |title=Direct measurement of the size, shape, and pole of 511 Davida with Keck AO in a single night |archive-url=https://web.archive.org/web/20070811073647/http://www2.keck.hawaii.edu/inst/people/conrad/research/pub/d511.pdf |archive-date=11 August 2007|bibcode=2007Icar..191..616C }}</ref> Mediumgrootte-asteroïdes soos Mathilde en [[243 Ida]] wat van naby waargeneem is, onthul ook ’n dik laag los materiaal wat die oppervlak bedek.
 
Asteroïdes word weens [[ruimteverwering]] donkerder en rooier namate hulle ouer word.<ref>{{cite web |title=University of Hawaii Astronomer and Colleagues Find Evidence That Asteroids Change Color as They Age |work=University of Hawaii Institute for Astronomy |date=19 Mei 2005 |url=http://www.ifa.hawaii.edu/info/press-releases/Jedicke_asteroids5-17-04.html |access-date=27 Februarie 2013 |language=en |archive-url=https://web.archive.org/web/2019092802065420191026203903/http://www.ifa.hawaii.edu:80/info/press-releases/Jedicke_asteroids5-17-04.html |archive-date=2826 SeptemberOktober 2019 |url-status=live|df=dmy-all}}</ref> Daar is egter bewyse dat die kleur vinnig verander, binne die eerste honderdduisend jaar, en dit beperk die nuttigheid van spektrummetings om asteroïdes se ouderdom te bepaal.<ref>{{cite web |title=Sun damage conceals asteroids' true ages |author=Rachel Courtland |work=New Scientist |date=30 April 2009 |url=https://www.newscientist.com/article/dn17062-sun-damage-conceals-asteroids-true-ages.html |access-date=27 Februarie 2013 |language=en |archive-url=https://web.archive.org/web/20150620140650/http://www.newscientist.com/article/dn17062-sun-damage-conceals-asteroids-true-ages.html |archive-date=20 Junie 2015 |url-status=live|df=dmy-all}}</ref>
 
== Tipes asteroïdes ==