Aa_d HH $ @d HHHHff@  d Footnote TableFootnote**.\t.\t/ - :;,.!?`9`TOCHeading1Heading2  EquationVariables65E<55Y6Q6m6 7f686s9u6v:6;6= ) I > )<$lastpagenum> *<$monthname> <$daynum>, <$year>4z +"<$monthnum>/<$daynum>/<$shortyear> ,;<$monthname> <$daynum>, <$year> <$hour>:<$minute00> <$ampm> -"<$monthnum>/<$daynum>/<$shortyear> .<$monthname> <$daynum>, <$year> /"<$monthnum>/<$daynum>/<$shortyear> 0 <$fullfilename> 1 <$filename> 2 <$paratext[Title]> 3 <$paratext[Heading1]> 4 <$curpagenum> 5 <$marker1> 6 <$marker2> 7 (Continued)d 8+ (Sheet <$tblsheetnum> of <$tblsheetcount>)loo 9Heading & Page <$paratext> on page<$pagenum> :Pagepage<$pagenum>9 ;See Heading & Page%See <$paratext> on page<$pagenum>. < Table All7Table<$paranumonly>, <$paratext>, on page<$pagenum> =Table Number & Page'Table<$paranumonly> on page<$pagenum> E FFA f HHAv JJ LL NN PP RA$  Xc5y  soe>5|  s > 5  ui> 5 t"5 ! u/um5 " ta5 # }n$d5 $ x se5 % ~ so>/5 & ~ s$ea5 ' ~ sfi5 ( s 5 ) s 5 * } xele5 + ~ yte5 , ~ y]5 - {g5 . y ya5 / y {a5 0 y yod)5 1 y+t 5 2 yu<$5 3  ynoo5 4 y ynge5 5 yx p5 6 yu5 7 yeen5 8 yHe5 9 ye<5 : y e5 ; y5 < ye5 = y yl$p5 > y yo<5 ? yTa5 @ y&'5 A yay>5 B yp>5 C yE5 D y yF5 E y y 5 F y y5 G y y5 H yJ5 I y y5 J z y5 K z z5 L z z5 M z6 N zR6 O z z$ X6 P zs6 Q zs6 R zu6 S zt6 T z wu6 U zt6 V }6 W x6 X z~6 Y z~6 Z z~6 [ z6# \ z6& ] z}6> ^ z z~6? _ z~6@ ` z z6A a zy6B b z zy6C c zy6D d z z6E e z z6K f z6o g y6p h 6q i 6r j 6y k 6~ l z z6 m 6 n | z6 o z6 p zy6 q zy6 r 6 s z6 t z z6 u z z6 v z6 w z zy6 x z zy6 y zy6 z zy6 { z z6 | z zy6 } z zz6 ~ z zz6  zz5X5dq5z$PF6dq6tLH6dq7x8C6Hm3R q897 Hm3R H RH R FootnoteHr@ q98:7 @ zHr@ HzHz  Single LineH'q:9<7E z;;Footnote  5_;:     HD q<:=7 6HD HH  Double LineH q=<@76>? Double Lineu z5c>?=y5e?>=66 zH q@=B7AA Single Line$5hA@HZqB@C7q TableFootnoteEGxR qCB7 9EGxR EPwEPw  TableFootnoteod5pDRRHH5xE5 HH EFe   HH5zFN5 HHlEE DHH5{G6 HH @>?HDoe   HH5}HJ6HHlGG HUV 5~I6 HUV AAJUU`   HUV 5JLH6HUV lII H$ 5K6 FtnH$ ELUU` tn oH$ 5LJ6H$ lKK HUV 5M5 HUV N UUe !  HUV 5NPF5HUV lMM H$ 5O5 H$ P UUe "  H$ 5PN5H$ lOO HH5QD HHLAR  ` # Spectral Classification UVC ` * of Stars n ` $  ` % , Based on what stellar spectra look like ` +  ` & , Defined before the physics was understood ` ,  J` '  Recall the physics so far: "` . K ? ( -(1) General shape (intensity as a function \ ( &of wavelength) similar to a blackbody y@ ( ! spectrum. ` - 5  ) +(2) Atomic absorption lines superimposed @ ) on top of the general shape. ` /   ` 0  ' 1 3Today:  Define spectral classes and relate them $D@ 1 =to the  temperature  and  luminosity  of a star. HH5RDHHlUQQ d5SUUicioHH5TS HH!t stellaUk  ` 2 Spectral Classifications C ` 3 pThe general idea of` 4 , ` 6 'Which absorption lines are fa` 5 . Present? ` 7 (1 Missing? s` 8 s Strongest? \` 9 of Weakest? )` : kb 1` ; !(  The Harvard Classification Scheme N` < AtTemperature k` = ed ` >  n` D l  p` ? /$How broad are the absorption lines? ` @ y: ` A la  The Morgan-Keenan Classes ` B Luminosity HH5USHHlRXTT ld5VXXHH5WV HH@  !YYX  C Harvard Classification and ` 2C @ C ss Temperature f` E Th e F 1Question:  Is the temperature high enough so i H F :that the following is possible for the gas atoms? 5 e` G s  t` H +Answer:   Yes, if  D E  kT  ` I !  f`` J asHNote:  D E >> kT    Level E 2  not excited edf` f`` K >C D E << kT    Excite levels higher than E 2 he ` L   M 1Therefore, absorption lines come and go as the e8@ M Btemperature is increased. HH5XVHHlUdWW H5YVZbW5Ѽuc5Z\YѼucѼu4uu$c5[\]Y Cu$cssicauu$Ѽuc5\Z[Y EѼuc FѼu4u=uqC5][^Y =uqC=uk=uk E 1=uC5^]_Y Gs =uC=u"dZ=u"dZ E 2RG5_^`Y I !RGZZ YhHhv5`_bY noYhHhvYhXdZYhXdZ D E=E 2 - E 1 d6add M IBbM6b`Y tIBbMZZ Thermal Energy  HH6ca HHy ffd ` N Magnitude and A0 Stars ;` O  X h P *Recall our definition of magnitude:7  Q 5Defines the  difference  between one magnitude i@ Q 6and another, but what defines  zero magnitude ? ` R Ѽu 7 S C/The answer is historical, and may be different T@ S )for different textbooks and astronomers: q` T   U dZ5 Old answer:  The star Vega ( a -Lyra) has I@ U G(apparent visual magnitude V    0 ` V   X Ў1 A Modern answer:  Find A0 stars (like Vega) @ X Hwith U - B = B - V =0  and correct for distance bM ` W  1 ` Y BRecall Zeilik Table 11-1: G ` Z  U = m( l350  nm) ] ` [  B = m( l430  nm) s ` \  V = m( l550  nm) HH6daOHHlXicc  ݀ 6 efiern*8R뫐SI(݀ 7'equal[(*q"Blue"q*)plus[(*q"Blue"q*)indexes[(*q"Blue"q*)0,1,char[(*q"Blue"q*)m],num[(*q"Blue"q*)1.00000000,"1"]],minus[(*q"Blue"q*)indexes[(*q"Blue"q*)0,1,char[(*q"Blue"q*)m],num[(*q"Blue"q*)2.00000000,"2"]]]],times[(*q"Blue"q*)num[(*q"Blue"q*)2.50000000,"2.5"],log[(*q"Blue"q*)id[(*q"Blue"q*)over[(*q"Blue"q*)indexes[(*q"Blue"q*)0,1,char[(*q"Blue"q*)F],num[(*q"Blue"q*)2.00000000,"2"]],indexes[(*q"Blue"q*)0,1,char[(*q"Blue"q*)F],num[(*q"Blue"q*)1.00000000,"1"]]]]]]]ikeNk6 fa eec7 ndd6'g iilleiHH6(hg  HH mB = mmi   ` ] Gravitation in Stars 5;` ^  X _ 0Question:  A star is a big ball of gas. Why u@ _ cdoesnt it just blow away? ` ` i r` a 'Answer:  Gravity holds it together! lue` b q* d c ,10Question:  If gravity holds it together, why "]@ c *) doesnt the star just collapse? lu#` d ue )@ e ,t4Answer:  The internal pressure of the gas pushes [(] e Bl1itself outward and counteracts gravity. This is [z H e [(.called  hydrostatic equilibrium :6 HH6*ig000HHldlhh  d6Ljll HH6Mkj HHpul ` g Hydrostatic Equilibrium ]P` h inSpherically Symmetric Star  |` i  u j i7Consider a small volume  dV=Adr  inside the star it j [at radius  r . The  density  at radius  r  is  r (r)   and @ j &the  pressure  is  P(r) . * h k er 9: HH6OljlseHHlikk ThH6Pmgvn}h6rdnd?~~6Vnom e-??~~Z6y6Yonqm$6 6yZ6I6_ptsm 6IdZdZ Forcel6[qorm6Ml lcH?6\rqtmcH?c]6`spvm nSp]dZdZ  of gravity-6-6^trpmvum-6-inse D-ZNz6tuj ]~~k9r udSh6bvswm judShuuuu Outward*u|QO6cwvxm u|QOuu PressureM7C\6dxwym hM7C\MHMH InwardMOQO6eyxzm MOQOM`M` PressureMgn6fzy{m 6YMgnMxMx (a little lessML6g{z|m sMLMM than theMSh6h|{}m MShMM OutwardlMYM6i}|m MYMMM  Pressure)6u~u%Gu'atop[(*j4j*)equal[string["Outward Force from Pressure"],string["Inward Force from Gravity"]],equal[cross[minus[id[(*i1iq"Green"q*)plus[(*q"Green"q*)times[(*q"Green"q*)char[(*q"Green"q*)P],id[(*q"Green"q*)plus[(*q"Green"q*)char[(*q"Green"q*)r],times[(*q"Green"q*)char[(*q"Green"q*)d],char[(*q"Green"q*)r]]]]],minus[(*q"Green"q*)times[(*q"Green"q*)char[(*q"Green"q*)P],id[(*q"Green"q*)char[(*q"Green"q*)r]]]]]]],char[A]],times[char[G],over[times[char[M],id[char[r]],id[(*i1iq"Cyan"q*)times[(*q"Cyan"q*)char[(*q"Cyan"q*)d],char[(*q"Cyan"q*)m]]]],indexes[1,0,char[r],num[2.00000000,"2"]]]]],equal[minus[cross[id[(*i1iq"Green"q*)times[(*q"Green"q*)over[(*q"Green"q*)times[(*q"Green"q*)char[(*q"Green"q*)d],char[(*q"Green"q*)P]],times[(*q"Green"q*)char[(*q"Green"q*)d],char[(*q"Green"q*)r]]],char[(*q"Green"q*)d],char[(*q"Green"q*)r]]],char[A]]],times[char[G],over[times[char[M],id[char[r]],id[(*i1iq"Cyan"q*)times[(*q"Cyan"q*)char[(*q"Cyan"q*)rho],id[(*q"Cyan"q*)char[(*q"Cyan"q*)r]],char[(*q"Cyan"q*)A],char[(*q"Cyan"q*)d],char[(*q"Cyan"q*)r]]]],indexes[1,0,char[r],num[2.00000000,"2"]]]]],equal[(*q"Red"q*)minus[(*q"Red"q*)over[(*q"Red"q*)times[(*q"Red"q*)char[(*q"Red"q*)d],char[(*q"Red"q*)P]],times[(*q"Red"q*)char[(*q"Red"q*)d],char[(*q"Red"q*)r]]]],times[(*q"Red"q*)char[(*q"Red"q*)G],over[(*q"Red"q*)times[(*q"Red"q*)char[(*q"Red"q*)M],id[(*q"Red"q*)char[(*q"Red"q*)r]],char[(*q"Red"q*)rho],id[(*q"Red"q*)char[(*q"Red"q*)r]]],indexes[(*q"Red"q*)1,0,char[(*q"Red"q*)r],num[(*q"Red"q*)2.00000000,"2"]]]]]])NpH6wuj("Ck:har]6xi(*(3j$Gr'equal[(*q"Blue"q*)string[(*q"Blue"q*)"Mass inside r"],times[(*q"Blue"q*)char[(*q"Blue"q*)M],id[(*q"Blue"q*)char[(*q"Blue"q*)r]]],int[(*i2iq"Blue"q*)times[(*q"Blue"q*)num[(*q"Blue"q*)4.00000000,"4"],char[(*q"Blue"q*)pi],indexes[(*q"Blue"q*)1,0,char[(*q"Blue"q*)r],num[(*q"Blue"q*)2.00000000,"2"]],char[(*q"Blue"q*)rho],id[(*q"Blue"q*)char[(*q"Blue"q*)r]],diff[(*q"Blue"q*)char[(*q"Blue"q*)r]]],num[(*q"Blue"q*)0.00000000,"0"],char[(*q"Blue"q*)r]]]d6z")c"R"qHH6{ h[(HHT̰(*)G],overme ` f q*Application: Central Pressure ;` l "q hX n ha4Rough approximation for a star of  radius R  q*u@ n )2and  mass M . Take ` o 2 Integration in one giant step:  dr = R  f`` q / Zero pressure at r=R:  dP =- P c f`` m Gr! Density is the same everywhere B̰fP` p e *  r (r)=M/(4 p R 3 /3) ̰` r (* l-̰ h s 2iCentral pressure is then; [̰` t 00 "̰ u q*8This is very high!    Later we will see that this lu/̰ u "]3large pressure gives rise to the very high central q*)L̰@ u q*.temperature which generates the power source. HH6}HHll H6(J2aW'8equal[(*q"Blue"q*)indexes[(*q"Blue"q*)0,1,char[(*q"Blue"q*)P],char[(*q"Blue"q*)c]],times[(*q"Blue"q*)cross[(*q"Blue"q*)char[(*q"Blue"q*)R],char[(*q"Blue"q*)G]],over[(*q"Blue"q*)times[(*q"Blue"q*)char[(*q"Blue"q*)M],over[(*q"Blue"q*)times[(*q"Blue"q*)num[(*q"Blue"q*)3.00000000,"3"],char[(*q"Blue"q*)M]],times[(*q"Blue"q*)num[(*q"Blue"q*)4.00000000,"4"],char[(*q"Blue"q*)pi],power[(*q"Blue"q*)char[(*q"Blue"q*)R],num[(*q"Blue"q*)3.00000000,"3"]]]]],power[(*q"Blue"q*)char[(*q"Blue"q*)R],num[(*q"Blue"q*)2.00000000,"2"]]]],over[(*q"Blue"q*)times[(*q"Blue"q*)num[(*q"Blue"q*)3.00000000,"3"],char[(*q"Blue"q*)G],power[(*q"Blue"q*)char[(*q"Blue"q*)M],num[(*q"Blue"q*)2.00000000,"2"]]],times[(*q"Blue"q*)num[(*q"Blue"q*)4.00000000,"4"],char[(*q"Blue"q*)pi],power[(*q"Blue"q*)char[(*q"Blue"q*)R],num[(*q"Blue"q*)4.00000000,"4"]]]]]N}̰60;d6HH6 [q"HHofPue)P],char]] ` v *qApplication: Line Broadening a;` w ov (X y *q9What is the acceleration due to gravity ( g ) on eu H y *)the surface of a star?8 "q*` x e" n z 00=Consider stars with normal masses (M  M SUN ) " z "q3but with very different radii R. Large stars have "q*1@ z *)"much smaller values of  g . N` { nu *k h | 00-Therefore, the surface pressure gradient= r } m[0is much smaller for large stars. This leads to m[ } 00-narrow absorption lines. Also remember that cfPfP@ } ,n7large stars are bright  since L  R 2 . 6-fP` ~  JfP  3  Large (and therefore bright) stars have very gfP@  narrow absorption lines. HH6HHl NH6 oa8ov (6tn iH[-p=$'equal[(*q"Blue"q*)char[(*q"Blue"q*)g],over[(*q"Blue"q*)times[(*q"Blue"q*)char[(*q"Blue"q*)G],char[(*q"Blue"q*)M]],power[(*q"Blue"q*)char[(*q"Blue"q*)R],num[(*q"Blue"q*)2.00000000,"2"]]]]6 zͥd=$'equal[over[times[char[d],char[P]],times[char[d],char[r]]],times[char[G],over[times[char[M],char[rho]],power[char[R],num[2.00000000,"2"]]]],times[char[g],char[rho]]]NH6mbe=,n ard5Left2d6Rightd7(a ReferencebdDfPdSn dVdadgdj6dd a v6f a Body. f b  z Bulleted\t. f c CellBody. f d  CellHeading. f e V Footnote. f fT Heading1Body. f gT  Heading2Body. f hT   HeadingRunInBody. f i l yIndented. f j g Numbered.\t. f kE  Numbered1.\tNumbered. f l f TableFootnote. f mT   TableTitleT:Table : .  f nP TitleBody. f o T   TableTitleT:Table : . f p   CellHeading. f q  CellBody. f r   CellFooting. f s  Body. @ t  lHeader. @ u  blaFooter. f w gH.Body. f x $ Body. f y Body. f z dyH.Body. $$f { Body. $$f | H.Body. f } $ Body. f ~  Body. f  $Body. H$f  Body. f  Body. f Body. f  Body. f  H.Body. f $  Body. f $ Body. Hf  Body. f Body. f $ H.Body. f Body. f  H.Body. f  H.Body. f $ Body. f H.Body. f  Body. $Hf H.Body. $lf H.Body. f $  H.Body. $f H.Body. f H.Body. $f H.yBody. $lf .H.yBody. $~f .H.yBody.  (  Emphasis  EquationVariables )   ڝ  ڝ $ڝ $)   [  ڝ $)  )  ڝ ڝ )  ڝ w tu w ڝ w )  tu  ڝ  ڝ $)   ڝ ڝ )  ڝ uo&  tu  ڝ ڝ )  )  ڝ ڝ tu  ڝ w  Z Z Z Z Z  Z  Z  Thin Medium Double Thick@  Very Thin     oH p q rH p q rH p q rH p q rH p q rFormat A   oH p q rH p q rH p q rH p q rH p q rFormat B U e V UComment d BlackT!WhiteddAReddd Greendd  Blued Cyand Magentad Yellow  Times-Roman Times-Bold Times-ItalicHelvetica-BoldSymbolSymbolTimes-BoldItalicTimesc HelveticaSymbol RegularRegular BoldRegularItalicFB:O%}T7]L~n1:WFoڊ/Ċ`ɣl<}W"n3;tljTZU3^zhX%"~bq%ZQeRq es9Lfgt2d!