ffiffi PIaffiffi*mffiW Syst€il?'es R.Paul Butler oDERNAsrRoNoMy nEvEALsto us, for the first time in his_ tory, scenesfrom one end ofthe cosmosto theother. 377 We havepicturesque views of planetarysurfaces in our own solarsystem - asthis book amply demonstrates I I - and panoramasof adolescentdeep-field galaxies swarming near the limit of the observableuniverse . Beyond pro- viding pretty pictures, asronomy pracesour worrd and our brief human livesin their true conrexrs:as vanishingly tiny subplotsin a truly enormous cosmicplay. The curtain op*, *iri, a Big Bang synthesisof the chemicalelembnts that evenruallylead to self- replicating, competitivestructures of moleculeswe call *life.,, While we humans play out our brief bit parts, we yearn ro grasp the overall plot. Naturally we wonder whether there are worrds beyond those of our solarsystem. Are they numerousor rare? How many of thcm haveconditions ripe for biologyf These are not new questions. _ In the fourth century BC, the Greek philosopher Epicurus spoke boldly of the infinite worlds that logrcally ,.aroms,, followed from the infinite number of thar he postulated. His contemporary,Aristotle, differed, seeing Earth asthe unique center ofa perfect crystallinesky. Aristotle,s Earth-centered cosmosdominated Westernthought for more than 1,500 years.The notion ofotherworlds took hold "gain on\ after Copernicusyanked Earth from its centralposition and placed it in orbit around rhe Sun with other planets. A computer simulates the birth of a Soon lupitcr-size planet around various thinkers another star. realizedthat the starsmight be diirant sunsand thercfore might haveplanets of their own. For centuries thereafter, detecting these extrasolar plenet! seemed beyond all possibility. Shining by reflected light, such objects should be roughly a billion times (perhap s 22 to 25 magnitudes) fainter than their host stars. Moreover, they would appear separatedby lessthan a few arcseconds,at best, from even the neareststars in our stellar neighborhood. If extrasolarplanets exist, they are lost in the glare surround.inga )78 st.lr'sin).lgc. l-or thcsc rc.ls()ns.tlctcctinq .l l)l.lltct.sr isiLrlcor nlf f.lr-c(lliqltt tlircctlr lt.rsIong [r('('11.1 PiPc t]rc.rnr r I lorr cr cr.. .rstlcscrilrctl l.tter..rstr.ortorl]cr\ ll-c ()n tltc rcr.gc()l .l r.(.\(rlull(,t) ttt Il^111c1sl)( )tlilttl tcrltrt0loqr'. r In thc nrc.rntintc..l nunrirer of irrrlir.cctolrscr-r ing str..lrcqre\ h.rrclrccrr tleriscd ()\'cf the l:lstccr.ltrrr\..rnrl esl.rcci:rllr or1;1]11 llst fc* r'c.rrs,t() ()\'erc(t'tc thc c\trcr)tc tiiflicLrlticsl. dctcett'tl pl,rnetsorbiting c\cn thc rrc.rrcstot thc st.rrr.Irrrlircct tcch nr(lUcs ()lt focUs thr sll1tll[)crtrtrl)tti()ns th.rt .rpl.rrrcr It)p()sc\ on l-i.tttn'tl. visiblc A strrr llrd its rrrrsccnc()nlpilni()n orbit tlrcir shrrrcd 'l'ltc Its h()stst.ir. !cntcr 0l tI.lss. st.stcrrrrrror cs througlr slr.lcc is $,cll. crtrsing tlrc For crlrrplc. \t.Ir )Lrpitcr.rrtlt]rc SLut.rre lockcri inro.r gr.rrrT^r t() trrlcc.r rrohttlirrg p.rth rcross tlrc of thc skr.,()ltscrvers Pl:rrre tr(xrJl(i:rrec scek tri dcttct 'tr.rrarithcir e()rllr)()nccrtcf ()tl)1.lss. srat.c rltc SLrrr c\tris{)lJr plrUlcts .rstx)lr)ctric.rllr, bt. trickltrg thc strlr.s tirrr rs 1.050 rir'cs'r'rc rrroliorrsrr itlr Ireeisc positiotr.rl,,r.,.rrura,,,a,,,r. lr).rssi\cthl. f LrPitcr,tlrcir.tcrrtc*f .rrss is 1,050 tinrcscloscr -.r to thc Surr l.roint.rbour50,000 knr out sitlcthc sol.rrsprhcre . 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L.uropcan ol .i.3 li{lrt vc.lrs t()\\.trd pole .trtclAnreric.lt qr()rtp\ :rrc .tlsorlcsi grrr g thc North EcliPtic ilr [)r:rco $,0uld rr sp.r.c \(f t,l\ a()nrl)le\ rvolttrlc .tticr [r.rsctis'stcrtrs t() .t().it()r th.rrs.r'tls rcrrrolirrg thc cf.fi,cts()l.pr(,1)ct. nt('tt()t) ,f'st.rrs i,t ,i.,, ..,r,rt..r. .rrrtip.rr'.111.11. srrrrrlt'rrcrtrslr' ,{ cr.osstrr.rrks thc sol.rr\\ stcnl.\ ccrrtcl of.rttrss. Sirchsltcilitcs c'Lritr i.e rrrrirtrritrr crr.rrqlr sc.sr tlVtt\t() (1(.tc(I tltc ntrrehsnr.rllcr sicn.ll fiont l:.rr.tlt.sizctlIl.rrrcts !f()sslnqIt front ()t h()slst.lr\. WOBI]LIN(; PI-AN ET DI-.TECTI0NS ( )r cr tite l.rst l0 r'c.rr.solrrcrr crs lt.rrc nrost olicn sc.rrt.lrt.ritor c\trJs()l.lr pl.rr)cts Usinq I)0!!/t:t.rltttl.ti.ir.rr1rr,..\ontctir.)lr.s 1.1111.1j r-.rtii.rlrckrcjtr sl)cctr()se()l)\. rhisrntlircet,.lctcetiotr nrt.tlrrirl h,rs p.rid ofi'spcct.rcLrl.trl\'. 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A st:rr.tppro.rchcs ilnd light t Fryurr.i). .{s ,r \t.lr rPf r(,il(.lr(\ , rhsrl.r rccedcs fi.onr Flarth u,hile orbiting the tht, cr. 11sli.h1 ctrttcr 01 rrtrss it sharrs .flris \\ll\cs becolncVcrv rvith its Utrsccltc0nrp.1piqy115. induccs slrghtlVc()ntlll.csse(1. shorlcrtilrg tllc rr.rrc l)(r'r{)(jicl)opPlcr slrifts in the spcctrrrl lcttgthstorr lrd ( lincs th.rt cntcrgc fronr the stitr,s blrrcrcolors orrrcrsclt . .i. rltc st.trr.ccc(lc\ fi( )ll .ttrnrisplrc|c. I r:tcking thcse firiltute rr.,rYclcngthshifis I-.,rrtlr.tlrc rr:rrclcnqths.irc s.ith stilie-()f.the sligittltlcns,thcrrc(1 . ()l.r-c\t\Jrnfrt. .irl \l)citt ()of.tl)hrerr.thlt.s .I\tr()n()nlcr\fi) (letefntinc tltc st.tr.rrtfler Ihcst l)opgrlly.slrilis.rr.cr\(.fualltiltql\ 'il1,tt()n.llt(j tinr IltcSLrrrrrrrlrtrir.slrr tn tlrfD l() r\titll.ltt tltc rtr.trscsOl rrrtscen pl.lttets. .lirotllll.i nt lrqr\!Ll)lt(1. sil.l rlr.tr.relr.rLrlt (i!tcrtt()n (,1 .1 \ ii i l( lli .cd lLrpitcrrntlrr rro[r[llc r-ctlrrir.csnrc.l\urcntcnt prccisron of 379 .rlrout .l nr pcr sccorrri,()r.c.l\\ J()ur:ings1-rcct1. l.lris c:rusesthc u.rrclcngrhsot-sttriisht to chlnrrc br.I rncreonc pJfr in 100 r,-nl- li.rr. L'.til rcccrltl'sLrclr prccisi.'\\.es fir bcr'.(i rcach, bLrtit rs rrou p1r55iblc. 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For scrcr.rl tir:cittics tht. pr.ceirjonr rf J\tr(,n(,n)i(.tll)o;lplcr nrc.r-\Lrrcntrnts ,l.lrc h.trl bccn st:rllcd.rt rrbotrti00 rl pcr scconti. \\.JS l)r()[rlclI thirt VcrV,\.erV sn].rll clrtnues iIt .r sl.lcctr<lnteter,s rigurt 1 (abope )'ktdi<t irstron().lers rre'e fbund strong c'idc.ec c()lrdrtr()n(slreh trr,rt rt lcrst ls tcnrperiltrlre,prcssLtrc, arrcl tlrrce plarrets circle pSR r2s7+r2,a illLrntinationof. fist-spin'i'g puri* i,r trrc c..stclratir>rr tltc oirlis5I sfruri()us'.ir.rstrurne virgo (upper panel).