高一英语 课外知识扩读 Lives on Other Earth-size PlanetPAGELivesonOtherEarth-sizePlanetAnEarth-sizeplanethasbeenspottedorbitinganearbystaratadistancethatwouldmakesitnottoohotandnottoocold-comfortableenoughforlifetoexist,researchersannouncedSeptember29. Ifconfirmed,theexoplanet,namedGliese581g,wouldbethefirstEa...
PAGELivesonOtherEarth-sizePlanetAnEarth-sizeplanethasbeenspottedorbitinganearbystaratadistancethatwouldmakesitnottoohotandnottoocold-comfortableenoughforlifetoexist,researchersannouncedSeptember29. Ifconfirmed,theexoplanet,namedGliese581g,wouldbethefirstEarth-likeworldfoundresidinginastar'shabitablezone-aregionwhereaplanet'stemperaturecouldsustainliquidwateronitssurface.Andtheplanet'sdiscoverersareoptimisticabouttheprospectsforfindinglifethere. "Personally,Iwouldsay,myownpersonalfeelingisthatthechancesoflifeonthisplanetare100percent,"saidStevenVogt,aprofessorofastronomyandastrophysicsattheUniversityofCalifornia."Ihavealmostnodoubtaboutit." Gliese581gisoneoftwonewworldstheteamdiscoveredorbitingthereddwarfstarGliese581,bumpingthatnearbystar'sfamilyofplanetstosix.Theothernewfoundplanet,Gliese581f,isoutsidethehabitablezone,researcherssaid. Thestarislocated20light-yearsfromEarthintheconstellationLibra.Reddwarfstarsareabout50timesdimmerthanoursun.Sincethesestarsaresomuchcooler,theirplanetscanorbitmuchclosertothemandstillremaininthehabitablezone.EstimatessuggestGliese581gis0.15astronomicalunits(OneastronomicalunitistheaveragedistancebetweentheEarthandsun)fromitsstar,closeenoughtoitsstartobeabletocompleteanorbitinjustlessthan37days. Gliese581ghasamassthreetofourtimesEarth's,theresearchersestimated.Fromthemassandestimatedsize,theysaidtheworldisprobablyarockyplanetwithenoughgravitytoholdontoanatmosphere.JustasMercuryislockedfacingthesun,theplanetistidallylockedtoitsstar,sothatonesidebasksinperpetualdaylight,whiletheothersideremainsindarkness.Thislockedconfigurationhelpstostabilizetheplanet'ssurfaceclimate,Vogtsaid.Betweenblazingheatonthestar-facingsideandfreezingcoldonthedarkside,theaveragesurfacetemperaturemayrangefromminus31tominus12degreesCelsius,theresearcherssaid.
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