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.AME #LASS #(!04%2 $ATE !&AMILYOF0LANETS 3%#4)/. /UR3OLAR3YSTEM .ATIONAL3CIENCE %DUCATION3TANDARDS "%&/2%9/52%!$ !FTERYOUREADTHISSECTIONYOUSHOULDBEABLETOANSWER THESEQUESTIONS %3CABC s7HATARETHEPARTSOFOURSOLARSYSTEM s7HENWERETHEPLANETSDISCOVERED s(OWDOASTRONOMERSMEASURELARGEDISTANCES 7HAT)S/UR3OLAR3YSTEM /URSOLARSYSTEMINCLUDESOURSUNTHEPLANETSTHEIR MOONSANDMANYOTHEROBJECTS!TTHECENTEROFOURSOLAR SYSTEMISASTARTHATWECALLTHESUN0LANETSANDOTHER SMALLEROBJECTSMOVEAROUNDTHESUN-OSTPLANETSHAVE ONEORMOREMOONSTHATMOVEAROUNDTHEM)NTHISWAYOUR SOLARSYSTEMISACOMBINATIONOFMANYSMALLERSYSTEMS 345$94)0 $ESCRIBE !SYOUREADMAKE ACHARTSHOWINGTHEPARTS OFOURSOLARSYSTEMTHAT WEREDISCOVEREDINTHE FOLLOWINGTIMEPERIODS BEFORETHESTHES THESANDTHES 3UN -ERCURY 0LUTO %ARTH -ARS 6ENUS .EPTUNE *UPITER 3ATURN 5RANUS 4HEPLANETSANDTHESUNARESOMEOFTHEOBJECTSINOURSOLARSYSTEM (OW7AS/UR3OLAR3YSTEM$ISCOVERED 5NTILTHESPEOPLETHOUGHTTHATTHEREWEREONLY EIGHTBODIESINOURSOLARSYSTEM4HESEWERETHESUN %ARTHSMOONANDTHEPLANETS%ARTH-ERCURY6ENUS-ARS *UPITERAND3ATURN4HESEARETHEONLYOBJECTSINTHESOLAR SYSTEMTHATWECANSEEFROM%ARTHWITHOUTATELESCOPE /NCETHETELESCOPEWASINVENTEDHOWEVERSCIENTISTS WEREABLETOSEEMANYMOREBODIESINOURSOLARSYSTEM)N THETHCENTURYSCIENTISTSDISCOVEREDSOMEOFTHEMOONS OF*UPITERAND3ATURN5RANUSANDSEVERALOTHERMOONS WEREDISCOVEREDINTHES.EPTUNEWASDISCOVEREDIN THES0LUTOWASNOTDISCOVEREDUNTILTHES 34!.$!2$3#(%#+ %3A 4HEEARTHISTHETHIRD PLANETFROMTHESUNINASYSTEM THATINCLUDESTHEMOONTHESUN EIGHTOTHERPLANETSANDTHEIR MOONSANDSMALLEROBJECTS SUCHASASTEROIDSANDCOMETS 4HESUNANAVERAGESTARISTHE CENTRALANDLARGESTBODYINTHE SOLARSYSTEM.OTE)N THE)NTERNATIONAL!STRONOMICAL 5NIONRULEDTHAT0LUTOISNO LONGERCONSIDEREDTOBEA PLANET )DENTIFY ,ISTTHREEKINDS OFOBJECTSTHATMAKEUPOUR SOLARSYSTEM #OPYRIGHT©BY(OLT2INEHARTAND7INSTON!LLRIGHTSRESERVED )NTERACTIVE4EXTBOOK !&AMILYOF0LANETS .AME 3%#4)/. #LASS $ATE /UR3OLAR3YSTEMCONTINUED (OW$O3CIENTISTS-EASURE,ONG$ISTANCES BVi];dXjh #ONVERT 3CIENTISTS DISCOVERANASTEROIDTHATIS !5FROMTHESUN(OWFAR INKILOMETERSISTHEASTEROID FROMTHESUN BVi];dXjh 2EMEMBERTHATASTRONOMERSUSELIGHTYEARSTOMEA SURELONGDISTANCESINSPACE4OMEASUREDISTANCESWITHIN OURSOLARSYSTEMASTRONOMERSUSETWOOTHERUNITSTHE ASTRONOMICALUNITANDTHELIGHTMINUTE /NEASTRONOMICALUNIT!5ISTHEAVERAGEDISTANCE BETWEENTHESUNAND%ARTH4HISDISTANCEISABOUT KM%ARTHIS!5FROMTHESUN.EPTUNEIS ABOUT!5FROMTHESUN4HEREFORE.EPTUNEISABOUT KMKMFROMTHESUN !NOTHERWAYTOMEASUREDISTANCESINSPACEISBYUSING THESPEEDOFLIGHT,IGHTTRAVELSATABOUTKMSIN SPACE)NONEMINUTELIGHTTRAVELSABOUTKM 4HEREFOREONELIGHTMINUTEISEQUALTOABOUT KM,IGHTFROMTHESUNTAKESMINUTESTO REACH%ARTH4HEREFORE%ARTHISLIGHTMINUTESFROM THESUN 3UN %ARTH LIGHTMINUTE #ONVERT !BOUTHOWMANY LIGHTMINUTESFROMTHESUNIS .EPTUNE ASTRONOMICALUNIT /NEASTRONOMICALUNITEQUALSABOUTLIGHTMINUTES (OW)S/UR3OLAR3YSTEM$IVIDED !STRONOMERSDIVIDEOURSOLARSYSTEMINTOTWOMAIN PARTS4HESEPARTSARECALLEDTHEINNERSOLARSYSTEMAND THEOUTERSOLARSYSTEM 4(%)..%20,!.%43 4HEINNERSOLARSYSTEMCONTAINSTHEFOURPLANETSTHAT ARECLOSESTTOTHESUN-ERCURY6ENUS%ARTHAND-ARS 4HEINNERPLANETSAREALSOSOMETIMESCALLEDTHE TERRESTRIALPLANETS4ERRESTRIALMEANShLIKE%ARTHv-ERCURY 6ENUSAND-ARSARELIKE%ARTHBECAUSETHEYHAVEDENSE ROCKYSURFACESAS%ARTHDOES4HEFIGUREONTHETOPOFTHE NEXTPAGESHOWSTHEORBITSOFTHEINNERPLANETS #OPYRIGHT©BY(OLT2INEHARTAND7INSTON!LLRIGHTSRESERVED )NTERACTIVE4EXTBOOK !&AMILYOF0LANETS Name SECTION 1 Class Date Our Solar System continued The Inner Planets TAKE A LOOK Earth 4. Identify Which of the inner planets is closest to the sun? Mercury Venus Sun 5. Identify Which of the inner planets is furthest from the sun? Mars THE OUTER PLANETS The outer solar system contains four planets: Jupiter, Saturn, Uranus, and Neptune. The outer planets are very different from the inner planets. The outer planets are very large and are made mostly of gases. Therefore, Jupiter, Saturn, Uranus, and Neptune are sometimes called the gas giant planets, or simply the “gas giants.” The distances between the outer planets are much larger than the distances between the inner planets. For example, the distance between Jupiter and Saturn is much larger than the distance between Mars and Earth. The figure below shows the orbits of the outer planets. Critical Thinking 6. Compare Give two differences between the inner solar system and the outer solar system. The Outer Planets Neptune Jupiter Inner Planets TAKE A LOOK Saturn 7. Identify What planet is farthest from the sun? Uranus Copyright © by Holt, Rinehart and Winston. All rights reserved. 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Scientists do not know if Pluto formed along with the planets. AN UNUSUAL ORBIT The shape of Pluto’s orbit is different from the shapes of the orbits of the outer planets. As shown in the figure below, sometimes Pluto is closer to the sun than Neptune is. At other times, Neptune is closer to the sun. 3ATURN *UPITER TAKE A LOOK 10. Compare How is Pluto’s orbit different from the orbits of the outer planets? 5RANUS .EPTUNE 0LUTO The shape of Pluto’s orbit is very different from the orbits of the outer planets. Facts About Pluto Distance from sun 39.5 AU Period of rotation 6 days, 10 hours Period of revolution 248 Earth years, 4 days Diameter 2,390 km Density 1.75 g/cm3 Surface gravity 6% of Earth’s A LARGE MOON Pluto’s moon, Charon, is more than half the size of Pluto. From Earth, it is hard to separate the images of Pluto and Charon because they are so far away. Charon may be covered by frozen water. Critical Thinking 11. Infer How do you think scientists learned that Pluto has a moon if it is difficult to separate their images? Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 419 A Family of Planets .AME #LASS $ATE 3ECTION2EVIEW .3%3 %3CAB 3%#4)/.6/#!"5,!29 GASGIANT APLANETTHATHASADEEPMASSIVE ATMOSPHERESUCHAS*UPITER3ATURN5RANUSOR .EPTUNE )DENTIFY 7HATISTHEMAINELEMENTFOUNDINTHEATMOSPHEREOFAGASGIANTPLANET #OMPARE &ILLINTHEBLANKSTOCOMPLETETHETABLE 0LANET $ISTANCEFROMSUN 0ERIODOFREVOLUTION !5 %ARTHYEARSDAYS !5 %ARTHYEARSDAYS !5 %ARTHYEARSDAYS !5 %ARTHYEARSDAYS %VALUATE$ATA (OWARETHESURFACETEMPERATUREANDLENGTHOFYEARONAPLANET RELATEDTOTHEPLANETSDISTANCEFROMTHESUN -AKE#OMPARISONS (OWDOTHEGASGIANTSDIFFERFROMTHEINNERPLANETSOFTHE SOLARSYSTEM)NYOURANSWERDISCUSSCOMPOSITIONSIZEDISTANCEFROMTHESUN LENGTHOFAYEARANDSOLARENERGYRECEIVED )DENTIFY 7HATGIVES.EPTUNEAND5RANUSTHEIRBLUETOBLUEGREENCOLORS $ESCRIBE 7HATDIDTHE6OYAGERPROBESDISCOVERABOUT*UPITER #OPYRIGHT©BY(OLT2INEHARTAND7INSTON!LLRIGHTSRESERVED )NTERACTIVE4EXTBOOK !&AMILYOF0LANETS .AME #(!04%2 #LASS $ATE !&AMILYOF0LANETS 3%#4)/. -OONS .ATIONAL3CIENCE %DUCATION3TANDARDS "%&/2%9/52%!$ 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