The Solar System 81

THE SOLAR SYSTEM

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N jiionjl Gcogrjphic Socicty

c*m«t u cm<iw* m»%ecvr

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Bcms iv i mi vioitvi nt e i u of eomc Kmg-loet eiar. our *»>lar ey elem began lo cvofvc uhen cepunding dcbhe from a ncarby eupcmoe J C epIoeMM pae*cd ihrough a e aei ten ■ uoue cloud of gae .md duet morę ihan 4 f> billion ycare agei Comprceeion. crcalcd by ihc dying elar‘e ehock w aece. tnggcccd Ihc Cdlapeę uf Ihc gae cloud. and ile own eclf-graeil> potted >1 li>-gdher et ilhan ince ilablcioctcaecindcnuiy and Icmpcralurc. Wuhm ihc Mink eif a coemtc ty*. Ihc cl**ud tod bccomc a rmalingdiek of gae and i.ipin/ed duet grame Ihc hub*eixild bccomc a ncw Mar. ihc *un: Ihc diek wouM generale Ihc planet eand Ihcir eatclluc*. ihc aelcroide. and Ihc comcte Ihal make upour eobr eyelem.

Ae ihc diek cooicd. eahoue materiale eon-deneed from ihc ckmd: liny grame of erficatce. metale, and Kce of walor. CarKm dmodc. mclhanc. and ummortia Whcn Ihcec collided. Ihcy coatceccd.

Sooaonly brgct Nnliceremamed. Ihe-nowie fornxd eun. ehinmg al fuli hntluncc. lud drn cn moel of Ihc rcmauung duel and gae inni inlcrcicllar epacc by mcane of ihc eolor wind— elrcame of rapidly nwiemg atonie particie e— and Ihc pcreletCOl preeMire of ile ow n light Sue-vivmg bodtce coniinoed lo ceiltidc and grow Becautc fhcy couleeced al diffcrcnt dniancc* from Ihc eun'e hcal. Ihcy eancd m compoeii «.o

Today in Ihcdark frmgce «tf ihc eyetem. hiue-ly wilhm Ihc eun'e graiiiat.sm.il gra*p. a«v objecie compoecd modły of tece—thc comcte. They oidc unii! dielurbed by a paeeiog etat, Ihcit alicrcd p.iih may bnng ihcm neater lo ihc eun. aflcr wtuch moel relurn lo recnotc region* of ihcir origio.

Separaling ihc miler and outer plancie arc ihc aelcroide. rock fragmcnle rurapng in *i/c from 1,00H km lo Icee ihan one km acroee Aeicroale. Iikc comcie. arc ptobably euremng floleam from Ihc carte eołar eyelem

Kour tcrrceinal. or canhlike. plancie mh.ibei Ihc mner parł of our eeilar eyelem. Each ie a eoł-id epNetC wilh a mcullic corc euiioundcd hy ehcUe of eilicalce. rcłatiedy dcplclcd of voła-Idce Ali were craicrcd by mclcetnlce and ałiec w uh eokumem and Carth*|uakC' in t* nie» puel kolca noc* cehalcd Ihe ga*ce iNat brcunic Ihc aimoepbcrce ceielmg today on Vcnue. Earlh. and Marę The aimoephcrc eif Marę. primariły carbondioeidc. hae a eurfacc prceeore Icee Ihan cmc-hundrcdlh ihal of tunh. whde Ihc almo-epherc eif Vcnue. ałeo inoeily CO;, prodocce a cruehtng eurfacc preeeoic ncarty a hundred timce out o w n Mctcury ie airlcee. eo email and cielec IO Ihc eun lh.il Ile ga*Ce WCfC l|UrCkly Idei loegucc.

The pani ouler plancie contam W pcrccnl of ad malcnal in Ihc eolar eyslcm, eecludin* ihc eun. Eacb ie a huge epheroid of piece—hydro-(CO and helium w Uh eomc mclhanc. ammoma. waicr. and olher eołalilce. Bcncalh cloud by-cre. gaecoue hydrogen bccomce incrcaeingly denee—al one potni beceimmg IujokI and. al etill grcalcr dcplhe in Jupiter and Saturn, ehang-mg lo a metal lic elalc Ali four plancie probohly havc córce of eilicalce. metale, and water. fitccpl for LlraiMle. ihc glant pbnete radutc morę hcal hack iało epacc ih.m Ihcy abeeirb from Ihc »un I hie rc««due of prunorduil eocrgy. Ich in« from Ihcir crralion. ie like Ihc warmth fromdymgcoule.

Many of ihc rcgular witclluce of thc pani planetv— ihoec ihal formed along w uh thc plan-Cl a* oppoecd lo bcing caplurcd latcr—arc larpc cnough lo Ne coneidcrcd pkuicis ihcmwNo. Ihc four latgc moone of Jupiter have \ilicalc córce and. with ihc ceccpuon of lo. arc M»r-roundcdby ebclleof łcc and pouitfy lupaid walet. lo. raging wuh eulfor and eulfur dweidc yotcaniim. ie ihc ooły body oihcf ihan Eanh know n locehiNt actiec vołcanoce Pluło. wuh ite larjc eatdfatc. ChtfM. takce on Ihc dunKWMkt of a double planet Piało hae a Ihio almoephcrc of nectluinc gae. and Kolh Nedic* may be compoecd of KCe euch oe mclh-anc Ortwling at Ihc outer edge of Ihc planclari realni. Pluło may u cli be a UMMtion objęci hc-I w cen plancie and COOKU.

HKMIHIKII C.CC4IIH Mnnaieliii n imiumciiwu leniwn o» ouini. I«w*

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