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TheSunandStars Thesunisthecenterofoursolarsystem. Forthousandsofyears,thesunhasbeenrevered,honored,andmisunderstood. Oursunisamid-rangesizestarthathasbeeninexistenceforbillionsofyears. Itisthecloseststartoearth. Thesunis93millionmilesawayandtakes8minutesforsunlighttoreachus. Let’stalkaboutthebirthanddeathofstarsbeforediscussingourmostimportantstar-thesun. Birthofastar • Starsbeginlifeinswirlingcloudsofgasanddustcallednebulae. • Thiscloudofdustismadeupofhydrogenandheliumthatcanbetrillionsofmilesacross. • Astronomersstudyingtheskysometimesseethesecloudsandmistakethemforgalaxies. • Nebulaecomeinavarietyofshapesandsizes.Somearenamedbecauseoftheshapethattheyform. • Thesecloudsgraduallyshrinkasgravitypullsthedustandgastogether. • Atthecenter,thegasgetshotterandhotteruntilanewstarisborn. • Starsbegintheirliveswhentheystartmakingenergy.Whenthedustandgasgetspulledtogethertightlyitgets veryhot. • Theenergymakesthestarshine,givingoutheatandlightliketheSun. • Eachnebulaecantake10millionyearstoformastar. • Sometimes,theextramaterialfromthestarformationbecomesasteroidsorcomets.Sometimesnewplanets areformedaroundthestar. • Imaginetheexcitementofastronomerswhentheyareactuallyabletowitnessthebirthofastar. • Whatisalightyear? • Alightyearisaunitofdistancethatmeasureshowfaralightcantravelinoneyear. • Itisusedinastronomytomeasurehowfarthingsarefromearth….inotherwords,howlongdoesittakefora planetorstarslighttoreachearth. • Sinceitonlytakessunlight8minutestoreachearth,itcanbesaidthatthesunis8lightminutesaway. • ThecloseststartothesuniscalledProximaCentauri.Thisstaris4.24lightyearsawayfromearth.Thismeans thatwhenweseethelightfromProximaCentauri,itwasactuallygeneratedalittlemorethan4yearsago. • Thereare32starsthatliewithin12.5lightyearsfromthesun.Theremainingbillionsofstarsthatyoucansee onaclearnightaremuchfurtheraway. TypesofStars • Inthenightsky,allstarslookliketinypinpricksoflight. • Inreality,starsvaryinsize,color,brightness,andlifespan. • Dwarfstars-Thesemakeupthemajorityofthestarsintheskyandarethesmalleststarsinhesky. • Mostdwarfstarsarereddwarfs. • Eventhoughtherearemorereddwarfstarsintheskythananyotherstar,theyaredifficulttoseebecauseof theirsizeandtheymakeverylittlelight. • Dwarfstarsaretheoldeststarsintheuniverse?Whyisthis? • Dwarfstarsarelesshotsoburnlessfuel.Thinkofaforestfire,whichisthehottestpart?Whichisthecoolest part? • Starsworkthesameway.Thecoolestpartisatthetopwhereitglowsred,thenexthottestpartisthemiddle whereitglowsorange/yellow.Thehottestpartisatthebase….wherethefuelis,whichglowsblue. • Wecandeterminehowhotastarisbasedonit’scolor. • Thehotterthetemperature,thequickerthestarwilldieorburnout. • Yellowstar-Thesearemediumsizedstarsthataresimilartothesun. • • • • • • Theyhaveamediumtemperature,causingthemtonotliveaslong. Don’tworry…thesestarscanliveupto10billionyears.Itisestimatedthatthesunis4.6billionyearsold.Itstill has5billionyearsoflifeleft. • Whenyellowstars(mediumsized)die,theyswellupbecomingverylarge.Wethencallthesestarsgiantstars. • Giantstar-Whensunsizedstarsbegintodie,theyexpand.Asthecenterofthestarburnsout,thehydrogen moleculesgetveryclosetogether.Thisignitesanewfuelwhichishelium. • Heliumburnshotterthanhydrogenandbeginstopushthestaroutmakingitlarger.Thinkofahotairballoon. Astheairinsidegetshotter,itstretchestheballoonoutfurther. • Manyofthestarsyouseeatnightaregiantstars. • In5billionyears,whenthesuntransformsintoagiantstar,itwillengulfMercury,Venus,Mars,andEarth. • BlueGiants-Thesearethehottestofthegiantstars.Becausetheyburnfuelsofast,theyburnoutinbetween 10,000-100,000years. • Thesestarsareincrediblybright.Whentheydie,theyexplodeinwhatiscalledasupernova. • SuperGiantStars-arethelargestofthegiantstars.IfthesunwereaSuperGiant,itwouldstretchallthewayto Uranus….about1.8billionmiles. • Whenagiantstarorsupergiantstardies,itbecomesablackhole.Wewilltalkmoreaboutsupernovasand blackholesinafewweeks. DeathofaStar • Starsbegintodiewhentheyrunoutofgastomakeenergy. • Themiddleofthestarshrinksbuttheouterpartsexpandmakingthestarmuchlarger. • Mostofthetime,starsdieapeacefuldeath.Theyswellup,shedtheirouterlayersanddisintegrateforminga planetarynebula. • Aplanetarynebulalookslikeabeautifulcolorfulcloud. • Planetarynebulaareusuallyvisiblefor50,000yearsbeforeitisabsorbedbytheatmosphere. • Whenagiantstardies,itcausesahugeexplosionknownasasupernova. • AccordingtoNASA,supernova’sarethelargestexplosionthatoccurinspace. • Asupernova,ordeathofagiantstaroccursaboutevery50yearsintheMilkyWaygalaxy.Supernova’smay occurabouteverysecondsomewhereintheuniverse.(Justanotherexampleofhowhugeouruniverseis). • Wewilltalkmoreaboutsupernova’sinafewweeks. • Ifthestarhasenoughweight,itwillbecomeablackhole.Ablackholeisoneofthemostmysteriousand powerfulforcesintheuniverse. • Ablackholeissomethingthatnothingcanescape…notevenlight. • Whenastarexplodesintoasupernova,thepowerandenergythatisleftoversinksinonitselfcausingablack hole….somethinglikeavacuum….butbillionstimesmorepowerful. • Wewilltalkmoreaboutblackholesinafewweeks. TheSun • Oursunisastar,butisclosertousthananyotherstar. • Likeallstars,thesunisahugeballofburninggas(hydrogen). • Withoutthesun,ourplanetwouldbelifeless. • Oursunstartedasababystarinanebula. • Overaperiodofmillionsofyears,gasanddustbegantoforminward(gravity)causingatremendousamountof heatandpressure. • Oncethis“babysun/star”becameatemperatureofaboutonemilliondegrees,itcausesnuclearfusion….which iswhenthiscelestialbodybeginstoburnit’sownfuel(hydrogen). • Thesunisfartoohotforastronautstovisit.Itisalsofartoobrighttoseewithatelescope. • Astronomersusespecialtelescopes/filterstoobservethesun. • • Theseobservationshavediscoveredanumberofthings. Thesunhasslightlycoolerareasthatwecallsunspots.Sunspotsappearslightlydarkerincolor. Ahighernumberofsunspotsgenerallyoccurevery11years.ThisisknownastheSaroscycle. Whiteareasonthesunareareaswherethetemperaturesarehotterthannormal. Therearetimeswhenthesunisveryactiveandreleasesmassiveamountsofgasintotheatmosphere.Theseare calledsolarflares. • Wecansometimesseethesesolarflaresinthenightsky. • Haveyoueverdrunkarootbeerquickly?Whatdoesitdotoyourbody? • Solarflaresarelikeagiantburp. • AuroraBorealisisthelightdisplaythatoccursfromthesun. • Whenthesesolarflareshitouratmosphere….whichismadeofmostlyoxygenandnitrogen…itcausesabeautiful lightshow. • Thereareveryfewplacesin2017thattheAuroraBorealis(Northernlights)canbeseen. • TheNorthernLightsorAuroraBorealiscanbeseeninFairbanks,Alaskafor250nightsduringtheyear. • ItcanalsobeseeninIceland,Norway,andSweden. • Thesouthernlights,orAuroraAustraliscanbeseeninAntarctica. Constellations • Aconstellationisagroupofvisiblestarsthatformapattern. • Theyhavebeenusedformanydifferentthings. • Thefirstuseforconstellationswasprobablyreligious.Manycivilizationsbelievedthatthestarswerehowthe godstoldstories. • Amorepracticaluseforconstellationswasinfarmingcultures. • PeoplebegantolearnthatwhenOrionwasfullyvisible,thatwinterwascomingsoon. • Thestarpatternsmadeiteasierforearlyfarmingculturestoknowwhentoplant. • ConstellationswerenamedfromtheGreeks. • Theyarenamesfrommythologicallegendsandheroes.Theyallhaveastorythatgoesalongwiththeirname. • Constellationswereusedduringourrecenthistorytoassistslaveswithescaping. • Therewasaslavesongcalled“FollowtheDrinkingGourd”thatgaveinstructionsforslavestoescape.Whatdo youthinkthedrinkinggourdreferredto? • • • • •