A theoretical look at the direct detection of giant planets(5)

However,the agshipoftheNASAOriginsprogram,theTerrestrialPlanetFinder(TPF

[66]),whosegoalistoimageplanetarysystemsandextrasolarEarthsandtoobtainlow-resolution(λ/ λ=10-20)spectrathatmayrevealinrudimentaryfashiontheO2,H2O,CH4,O3,orCO2signaturesoflife,willalsobeaformidableinstrumentfordirectlydetectingandcharacterizingEGPs.AsFig.5indicates,forangularseparationsbetween～0.05′′and～2.0′′,eitherthemore-straightforwardopticalcoronagraphicdesign(TPF-C)orthemulti-telescopeinfrared(5–20µm)interferometer(TPF-I/Darwin)woulddetectEGPsmuchmorereadilythantheextrasolarEarthsthatareitsprimarytargets.

Fortheclose-inEGPs,directimagingseemsoutofthequestionfortheforseeablefuture.However,thisdoesnotmeanthattheplanetary uxcannotbemeasured.Fromtheground,thereareavarietyoftechniquestousetheplanet-plus-starlighttodistinguishtheplanetarycomponent(particularlyforknownroasters).Theseinclude1)usingprecisionphotometrytoapartin105(!)tomeasurethephasevariationsofthesummedopticalornear-infraredlight,

Astronomy is at times a science of unexpected discovery. When it is, and if we are lucky, new intellectual territories emerge to challenge our views of the cosmos. The recent indirect detections using high-precision Doppler spectroscopy of now more than on

2)measuringthemotionofthelightcentroid,perhapsbestdoneinthemid-infraredwithanAntarctic30-metertelescope,3)spectraldeconvolutionofaknownEGP/starsystemusingitsRV-measuredvelocitiesandephemeris,and4)multi-frequencydi erentialinterferometricimaging(pioneeredforKeck,amongothers).FurthertransitstudiesofHD209458b(suchasledtothediscoveryoftheNa-DandLyman-αfeatures)arecertainlywarranted.Theground-basedmethodswillbechallenging,butlessexpensivethanspace-basede orts.However,thereiscurrentlyinspaceamicro-satellite,MOST[67],witha15-centimeteraperture,thatisdesignedtoachievephotometricaccuracyintheopticalofafew×10 6.Ithasonitscurrentobservingmanifestprogramstostareat51Pegb,τBoob,andHD209458b.Therehaveasyetbeennoannouncements.

VII.THEFUTURE

WithmanyprogramsofdirectplanetdetectionplannedonalargesubsetoftheLBT,VLT,Keck,Gemini,GMT,GSMT/CELT,andOWLonthegroundandHST,Corot,Kepler,MOST,SIM,Gaia,TPF-C,TPF-I/Darwin,ECLIPSE,EPIC,andJWSTinspace,duringthenexttwentyyearstherewillbeanincreasingcrescendoofnewresultsonextrasolarplanetsthatwillcompletelytransformourviewofthenatureofplanetarysystems.

EGPs,beingbrighter,arethenaturaltechnologicalandscienti csteppingstonesonthepathtoimagingextrasolarEarths.Wewillencounterthem rst.BoththeNASAandESAroadmaps[68]havegivenplanetdetectionprideofplace.Strategiesarenowbeingformulatedtoestablishalogicalsequenceofmissionsandtelescopeconstructionthatwilloptimizethepaceofdiscovery.Moreover,theoreticalworkinsupportofmissionplanningismaturingtothepointthatitmaybereadytointerpretwhatweobserve.However,atheorist’sprejudicesaside,onecan’thelpbutwonder:Whatisitwewillactually nd?Whatdiscoverieswillbemade?Asthehuntforworldsbeyondoursolarsystemquickens,anancientcuriositystirstoask:WhatwillourgenerationseefromthatfabledpeakinDarien[69]?

Astronomy is at times a science of unexpected discovery. When it is, and if we are lucky, new intellectual territories emerge to challenge our views of the cosmos. The recent indirect detections using high-precision Doppler spectroscopy of now more than on

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