byClaireDanielbyClaireDanielbyClaireDanielCover,DetlevvanRavenswaay/PhotoResearchers,Inc.;3,CourtesyofNASA;4,CourtesyNASA/JPL-Caltech;5,CourtesyofNASA/JPL-Caltech;6,CourtesyofNASA/JPL-Caltech;7,CourtesyofNASA;8,CourtesyofNASA;9,CourtesyofNASA/JPL-Caltech;10,CourtesyofNASA;11,CourtesyofNASA/JPL-Caltech;12,CourtesyofNASA/JPL-Caltech;13,DetlevvanRavenswaay/PhotoRe-searchers,Inc.;14,NavinPatel.Copyright©byHarcourt,Inc.Allrightsreserved.Nopartofthispublicationmaybereproducedortransmittedinanyformorbyanymeans,electronicormechanical,includingphotocopy,recording,oranyinformationstorageandretrievalsystem,withoutpermissioninwritingfromthepublisher.RequestsforpermissiontomakecopiesofanypartoftheworkshouldbeaddressedtoSchoolPer-missionsandCopyrights,Harcourt,Inc.,6277SeaHarborDrive,Orlando,Florida32887-6777.Fax:407-345-2418.HARCOURTandtheHarcourtLogoaretrademarksofHarcourt,Inc.,registeredintheUnitedStatesofAmericaand/orotherjurisdictions.PrintedintheUnitedStatesofAmericaISBN10:0-15-350593-1ISBN13:978-0-15-350593-5OrderingOptionsISBN10:0-15-350336-X(Grade6Below-LevelCollection)ISBN13:978-0-15-350336-8(Grade6Below-LevelCollection)ISBN10:0-15-357735-5(packageof5)ISBN13:978-0-15-357735-2(packageof5)Ifyouhavereceivedthesematerialsasexaminationcopiesfreeofcharge,HarcourtSchoolPublishersretainstitletothematerialsandtheymaynotberesold.Resaleofexaminationcopiesisstrictlyprohibitedandisillegal.Possessionofthispublicationinprintformatdoesnotentitleuserstoconvertthispublication,oranyportionofit,intoelectronicformat.1234567891017912111009080706Eversincehumansfirstlookeduptothestars,theyhavewonderedaboutspace.Withthehelpofspacetravel,landingonthemoon,andnewtechnology,wehavelearnedmuchinthepastcenturyaboutthesunandtheplanetsinoursolarsystem.TheSunEarthwouldbeadismalandbarrenplanetwithoutthewarmthofthesun.Thesunisanaverageof93millionmiles(150millionkm)awayfromEarth,yetitsendsenoughheattoallowplantstogrowandanimalstothrive.Thesunishugeandhasadiameterofalmost900,000miles(1,448,370km).The27,0...
