exoplanet

BringingthearchforanotherEarthaboutascloasitwilleverget,ateamof

EuropeanastronomerswasscheduledtoannounceonWednesdaythatithad

foundaplanetthesamemassasEarth’sinAlphaCentauri,atriplestarsystem

thatistheSun’sclostneighbor,only4.4light-yearsaway.

Theplanetisthelightestoneeverfoundorbitinganotherstarand—inthewords

ofitsdiscoverer,XavierDumusque,agraduatestudentattheGeneva

Obrvatory—“itwillsurelybetheclostoneever.”

Itispresumablyarockyballlikeourown,lesAlpha

CentauriB,areddishorbabouthalfasluminousastheSun,everythreedaysata

distanceofonlyaboutfourmillionmiles,resultinginhellishsurface

temperaturesof1,200degrees.

Sothisisnot“Earth2.0.”Yet.

Astronomerssaidthediscoveryraidthepossibilitythattherewerehabitable

Earthlikeplanetsrightnextdoorandthatmethodsandinstrumentswerenow

precienoughtodetectthem.

“Verysmallplanetsarenotrare,”ue,whoistheleadauthorofa

paperbeingpublishedonWednesdayinNature.“Whenyoufindonesmallplanet,

youfindothers.”HeandhiscolleaguesdiscusdtheresultsonTuesdayina

newsconferencehostedbytheEuropeanSouthernObrvatoryinGarching,

Germany.

Astronomerswereelectrifiedbythenewsoftheplanet,butalsocautionedthatit

neededconfirmationbyotherastronomers,notaneasytask.

DebraFischer,aYaleastronomerwhohasbeenarchingforplanetsinthatsame

systemforyears,said:“Thediscoverythatournearestneighborhasrockyplanets

isthestoryofthedecade.I’dbet$100thatthereareotherplanetsthatarethere

aswell.”

ThediscoveryalsounderscoredtheallureofAlphaCentauriasatargetofspace

andscientificexploration.

“Thisiscloenoughyoucanalmostspitthere,”saidGeoffreyMarcy,an

exoplanetastronomerattheUniversityofCalifornia,Berkeley.

SaraSeager,anastronomerattheMassachuttsInstituteofTechnology,saidin

ane-mail,“Ifeellikeweshoulddropeverythingandndaprobetheretostudy

thenewplanetandothersthatarelikelyinthesystem.”

entauriA,whichisslightlylargerand

brighterthantheSun,andAlphaCentauriB,slightlysmaller,areclo

companions,circlingeachotherandpassingascloasninebillionmilevery

turnarebeingcircledatamuchgreaterdistance,someone

trillionmiles,byadwarfstarthatisknownasProximaCentauribecauitis

slightlyclortotheEarth,duetothattrillionmiles,thantheothertwo.

Theso-calledhabitablezoneofAlphaCentauriB,wheretemperatureswouldbe

moderateenoughforwaterandcreatureslikeus,isabout65millionmilesfrom

thestar,whereayearwouldtake200daysorso,aboutthesameastheorbitof

Venusinourownsystem.

ueandhiscolleaguesfoundtheplanetbytheso-calledwobble

method,usingaspeciallybuiltspectrographcalledHARPSona140-inch

diametertelescopeattheEuropeanSouthernObrvatoryinLaSilla,Chile,to

trackthehoststarasitistuggedtoandfrobytheplanet’ouryears

and450obrvations,theyfoundthatinthecaofAlphaCentauriB,thattug

impartsavelocityofabout20inchesacond,aleisurelywalkingspeed.

ThatisthesmallestwobbletheSwissteamhaverobrved.

AplanetonlyfourtimesasmassiveastheEarthwouldproducethesameamount

ofwobbleifitwasoutinthehabitablezoneandwouldthusbedetectablebytheir

instrument,ouldtakealongtime.“Ifyouwantto

findaplanetat200days,”hesaidreferringtotheorbitalperiod,“youneed8to

10years.”

aidthiswasthekindofdiscoverythatcouldreigniteinterestinother

experimentsliketheTerrestrialPlanetFinder,aspaceobrvatoryforstudying

exoplanetsthatwasonceatthetopofNASA’swishlistbutisnowlanguishing.

Twoyearsago,iumwitha

bittercriticismofNASA,theNationalAcademyofSciencesandtheplanetary

co

wentontocallforaninternationalprojecttolaunchascientificprobetoAlpha

Centauri.

Itcouldtakehundredsofyears,butsuchamission,aid,couldjolt

NASAoutofitsdoldrums.

Thenewplanet,aid,“fitsrightintothatrant.”Hewenton,“Whata

greatscientificeducationalmissiontohaveaprobeoutthere,makingitsway

decadeafterdecade.”