Asteroïde: Verskil tussen weergawes
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====Grootste asteroïdes====
[[Beeld:The Four Largest Asteroids.jpg|thumb|Die grootste vier asteroïdes.]]
Hoewel hul ligging in die asteroïdegordel hulle van planeetstatus uitsluit, is die grootste drie voorwerpe – Ceres, Vesta en Pallas – ongeskonde protoplanete wat baie eienskappe met planete deel. Hulle is ook atipies in vergelyking met die meeste "aartappelvormige" asteroïdes. Die vierde grootste asteroïde, Hygiea, het ’n ongedifferensieerde interieur, nes die meeste ander asteroïdes.
Ceres is die enigste een met ’n ten volle [[Ellips|ellipsoïdale]] vorm en dus die enigste een wat ’n dwergplaneet is.<ref name=IAU2006/> Dit het ’n veel groter [[absolute magnitude]], van sowat 3,32,<ref>
{{cite journal
|display-authors=3 |author1=Parker, J.W. |author2=Stern, S.A. |author3=Thomas, P.C. |author4=Festou, M.C. |author5=Merline, W.J. |author6=Young, E.F. |author7=Binzel, R.P. |author8=Lebofsky, L.A.
| title=Analysis of the First Disk-resolved Images of Ceres from Ultraviolet Observations with the Hubble Space Telescope
| journal=The Astronomical Journal
| date=2002
| volume=123
| issue=1
| pages=549–557
| doi = 10.1086/338093 |doi-access=free
| bibcode=2002AJ....123..549P |bibcode-access=free
| arxiv=astro-ph/0110258
}}</ref> as die ander asteroïdes en kan ’n laag [[ys]] op die oppervlak hê.<ref name="planetary">{{cite web|title=Asteroid 1 Ceres|work=The Planetary Society|url=http://www.planetary.org/explore/topics/asteroids_and_comets/ceres.html|accessdate=20 Oktober 2007| archiveurl= https://web.archive.org/web/20070929092440/http://planetary.org/explore/topics/asteroids_and_comets/ceres.html| archivedate= 29 September 2007 <!--DASHBot-->| deadurl= no}}</ref> Nes die planete is Ceres se interieur gedifferensieerd: Dit het ’n kors, ’n mantel en ’n kern.<ref name="planetary" />
Vesta het ook ’n gedifferensieerde interieur, maar het binne die Sonnestelsel se [[vriesgrens]] gevorm en het dus nie [[water]] nie;<ref>{{cite press release |id=STScI-1995-20 |title=Asteroid or Mini-Planet? Hubble Maps the Ancient Surface of Vesta |url=http://hubblesite.org/news_release/news/1995-20 |website=Hubble Space Telescope |date=19 April 1995 |access-date=16 Desember 2017}}<br />{{cite press release |url=http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/20/image/c |title=Key Stages in the Evolution of the Asteroid Vesta |website=Hubble Space Telescope |date=19 April 1995 |accessdate=20 Oktober 2007 |archiveurl= https://web.archive.org/web/20080907192327/http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/20/image/c| archivedate=7 September 2008<!--DASHBot-->| deadurl=no}}</ref><ref>{{cite journal |title=Dawn mission and operations |last1=Russel |first1=C. |last2=Raymond |first2=C. |last3=Fraschetti |first3=T. |last4=Rayman |first4=M. |last5=Polanskey |first5=C. |last6=Schimmels |first6=K. |last7=Joy |first7=S. |journal=Proceedings of the International Astronomical Union |volume=1 |issue=S229 |pages=97–119 |url=http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=414750 |date=2005 |accessdate=20 Oktober 2007 |display-authors=3 |doi=10.1017/S1743921305006691|bibcode=2006IAUS..229...97R }}</ref> hy is hoofsaaklik uit [[Lawa|basaltrots]] soos [[olivien]] saamgestel.<ref>{{cite journal |last=Burbine |first=T.H. |title=Where are the olivine asteroids in the main belt? |journal=Meteoritics |date=July 1994 |volume=29 |issue=4 |page=453 |bibcode=1994Metic..29..453B |bibcode-access=gratis}}</ref> Buiten die groot [[krater]] by sy suidpool, het Vesta ook ’n ellipsoïdale vorm. Dit is die hoofvoorwerp van die Vesta-familie en ander V-tipe asteroïdes, en is die bron van die [[Achondriet|HED-meteoriete]], wat 5% van alle [[meteoriet]]e op Aarde uitmaak.
Pallas is buitengewoon omdat dit, soos Uranus, op sy kant roteer, met ’n groot [[Baanhelling|hoek tussen sy rotasie-as en wentelvlak]].<ref name="Torppa1996">{{cite journal |first1=J. |last1=Torppa |first2=M. |last2=Kaasalainen |first3=T. |last3=Michałowski |first4=T. |last4=Kwiatkowski |first5=A. |last5=Kryszczyńska |first6=P. |last6=Denchev |first7=R. |last7=Kowalski
| title=Shapes and rotational properties of thirty asteroids from photometric data
| journal=Icarus | date=1996
| volume=164 | issue=2 | pages=346–383
| bibcode=2003Icar..164..346T
| 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 |deadurl=yes |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 |accessdate=20 Oktober 2007 |archiveurl=https://web.archive.org/web/20071011154140/http://orbitsimulator.com/gravity/articles/ceres.html |archivedate=11 October 2007 |deadurl=yes |df=dmy-all }}</ref> Dit is die grootste lid en vermoedelik die hoofvoorwerp van die Hygiea-familie asteroïdes.
{| class="wikitable"
|- style="background:#ccf;"
! colspan="13" style="background:#ddd;"| Eienskappe van die grootste asteroïdes
|- style="font-size: smaller;"
!Naam
!Wentel-<br />radius<br />([[AE]])
!Wentel-<br />periode<br />(jaar)
![[Baanhelling|Helling tot<br />die sonnebaan]]
![[Eksentrisiteit (sterrekunde)|Baan-<br />eksentrisiteit]]
! Deursnee<br />(km)
! Deursnee<br />(% van [[Maan]])
! Massa<br />({{e|18}} kg)
! Massa<br />(% van Ceres)
! [[Digtheid]]<ref>{{cite book | url = http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3022.pdf | title = Asteroid Density, Porosity, and Structure | journal = Asteroids Iii | pages = 485 |accessdate=3 January 2013| bibcode = 2002aste.book..485B | last1 = Britt | first1 = D.T. | last2 = Yeomans | first2 = D. | last3 = Housen | first3 = K. | last4 = Consolmagno | first4 = G. | year = 2002 }}</ref><br />(g/cm<sup>3</sup>)
! Rotasie-<br />periode<br />(uur)
! [[Ashelling]]
! Oppervlak-<br />temperatuur
|- style="text-align:center;"
! style="text-align:left;"| Vesta
| 2,36
| 3,63
| 7,1°
| 0,089
| 573×557×446<br />(gemiddeld 525)
| 15%
| 260
| 28%
| 3,44 ± 0,12
| 5,34
| 29°
| 85-270 [[Kelvin|K]]
|- style="text-align:center;"
! style="text-align:left;"| Ceres
| 2,77
| 4,60
| 10,6°
| 0,079
| 975×975×909<br />(gemiddeld 953)
| 28%
| 940
| 100%
| 2,12 ± 0,04
| 9,07
| ≈ 3°
| 167 K
|- style="text-align:center;"
! style="text-align:left;"| Pallas
| 2,77
| 4,62
| 34,8°
| 0,231
| 580×555×500<br />(gemiddeld 545)
| 16%
| 210
| 22%
| 2,71 ± 0,11
| 7,81
| ≈ 80°
| 164 K
|- style="text-align:center;"
! style="text-align:left;"| Hygiea
| 3,14
| 5,56
| 3,8°
| 0,117
| 530×407×370<br />(gemiddeld 435)
| 12%
| 87
| 9%
| 2,76 ± 1,2
| 27,6
| ≈ 60°
| 164 K
|}
[[Beeld:masses of asteroids vs main belt.png|thumb|340px|links|Die relatiewe massas van die grootste 12 bekende asteroïdes,<ref name="Baer2011">[http://home.earthlink.net/~jimbaer1/astmass.txt "Recent Asteroid Mass Determinations"]. Maintained by Jim Baer. Last updated 2010-12-12. Besoek op 2 September 2011.</ref> in vergelyking met die oorblywende massa van die asteroïdegordel.<ref name="Pitjeva05">
{{cite journal
|last=Pitjeva
|first=E.V.
|authorlink=Elena V. Pitjeva
|title=High-Precision Ephemerides of Planets – EPM and Determination of Some Astronomical Constants
|journal=Solar System Research
|date=2005
|volume=39
|issue=3
|page=184
|url=http://iau-comm4.jpl.nasa.gov/EPM2004.pdf
|format=PDF
|doi=10.1007/s11208-005-0033-2
|bibcode=2005SoSyR..39..176P
|deadurl=yes
|archiveurl=https://web.archive.org/web/20140703074335/http://iau-comm4.jpl.nasa.gov/EPM2004.pdf
|archivedate=3 Julie 2014}}</ref>]]
{{clear}}
== Tipes asteroïdes ==
Die optiese eienskappe van 'n asteroïde lewer belangrike inligting oor sy aard an sy samestelling. Asteroïdes word volgens hulle spektrale eienskappe in verskeie tipes verdeel. Die drie belangrikste tipes is: S, M en C.<ref>Could an Asteroid Hit the Earth?: Asteroids, Comets, Meteors, and More {{Outeur|Rosalind Mist}} Heinemann-Raintree Library, 2006, ISBN 1-4034-7709-4, ISBN 978-1-4034-7709-5</ref>
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