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1、KeplerTelescopeDiscoversMostEarth-LikePlanetYetAnearlyEarth-sizeplanetorbitsinastar'shabitablezone,detectedbyNASAastronomers.Thisartist'sdepictionshowsKepler-186f,anEarth-sizeworldinthe"habitablezone"ofareddwarfstar.ILLUSTRATIONBYNASA/JPL-CALTECH/T.PYLEDanVerganoNationalGeographicPUBLISHED
2、APRIL17,2014Redsunshine,seas,andmaybealiens?ScientistsanalyzingdatafromNASA'sKeplerSpaceTelescopetodayreporttheclosestthingyettoanotherEarth,aworldinahabitableorbitaroundareddwarfstarsome493light-yearsaway.Source:http://news.nationalgeographic.com/news/2014/04/140417-earth-planet-kepler-ha
3、bitable-science-nasa/Launchedin2009withthegoaloffindinganotherEarth,the$600-millionKeplerspacecrafthasdiscoveredmorethan960planetsorbitingnearbystars.Halfadozenofthoseseemtoberocky,likeEarth,andhaveorbitsinthehabitablezonearoundtheirstar—butthenewlydiscoveredworld,namedKepler-186f,istheclo
4、sestinsizetoEarth."Thisisafirst,validatedEarth-sizeplanetinthehabitablezoneofanotherstar,"saysstudyleadauthorElisaQuintanaoftheSETIInstituteandNASA'sAmesResearchCenterinMountainView,California.ThediscoveryoftheplanetwasreportedtodayinthejournalScienceandinaspaceagencypressbriefing.(Related
5、:"MotherlodeofAlienWorldsRevealedbySpaceTelescope.")Oneoffiveplanetsorbitingareddwarfstar(calledKepler186),Kepler-186fis1.1timeswiderthanEarth.Thatmeansit'salmostcertainlyarockyplanettoo.Theresearchersestimateitsmassis1.5timesthatofEarth's.Thenewplanet'sorbit,meanwhile,placesitatthe"Goldil
6、ocks"distancefromitsstar—nottoohotortoocoldforliquidwatertoexistonitssurface.TheoriginoflifeonEarthrequiredliquidwater,notesstudyco-authorStephenKaneofSanFranciscoStateUniversity."Thisisanhistoricdiscovery—thefirstEarth-sizeplanetfoundinthehabitablezonearounditsstar,"sayspioneeringplanethu
7、nterGeoffMarcyoftheUniversityofCalifornia,Berkeley,whowasnotonthediscoveryteam."Thisisthebestcaseforahabitableplanetyetfound."Theplanet'sreddwarfstarisonlyabouthalfasbigasthesun,makingitcooleranddimmer.ButKepler-186fisonatighterorbitthanEarthis,takingonly130da
