Astronomy - Chapter 15 Test

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CHAPTER 15: The Milky Way Galaxy

1.Who was the first to look at the Milky Way with a telescope?A) Sir Isaac Newton C) Johannes Kepler B) Sir Willia !erschel ") #alileo #alilei

Ans$ "Section$ Intro%&ction to Chapter 1'

(. he Milky Way #ala*yA) is one of any +illions of ,ala*ies in the &ni-erse.B) is &ni &e in the &ni-erse in showin, %efinite spiral str&ct&re.C) contains the whole &ni-erse/ e-erythin, o+ser-a+le is within its -ol& e.") is one of only a few spiral ,ala*ies/ ost other ,ala*ies in the &ni-erse are

a orpho&s collections of stars shape% like ellipsoi%s.Ans$ ASection$ 1'01

. he fa o&s nineteenth0cent&ry o+ser-ational astrono er 2or% 3osse +&ilt the lar,est

telescope of his ti e 4an% %isco-ere% the spiral nat&re of any so0calle% 5ne+&lae6) inwhich co&ntry?A) 7n,lan% B) he 8nite% States C) Irelan% ") #er anyAns$ CSection$ 1'01

9. he first s&,,estion that there were collections of stars +eyon% o&r Milky Way in the&ni-erse was a%e +y

A) 7%win !&++le in 1:( .B) I an&el Kant in 1;''.C) Willia 9'.

") Sir Isaac Newton in 1 :@.Ans$ BSection$ 1'01

'. he i%ea that so e of the 5ne+&lae6 that are o+ser-e% in the sky i,ht +e 5islan%&ni-erses=6 i ense collections of stars far +eyon% the Milky Way= was first propose% +y

A) I an&el Kant in 1;''. C) !e+er C&rtis in 1:(@.B) Al+ert 7instein in 1:@:. ") 2or% 3osse in 1>9'.

Ans$ ASection$ 1'01

.Which concept concernin, the %iff&se o+ ects o+ser-e% +y !erschel was propose% +yKant in the 1;@@s an% was stron,ly s&pporte% +y o+ser-ations a%e in 1>9' +y the 7arlof 3osse with his worl%0class telescope in Irelan%?

A) Many of the %iff&se o+ ects in o&r sky are o-in, rapi%ly away fro o&r #ala*y.B) Many of the ne+&lae in the sky are separate entities +eyon% o&r Milky Way #ala*y.C) he %iff&se o+ ects o+ser-e% +y !erschel an% known as planetary ne+&lae were in

fact planets or+itin, other stars in o&r #ala*y.") All of the %iff&se ne+&lae seen in the sky are ,as clo&%s in o&r Milky Way #ala*y.

Ans$ BSection$ 1'01

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;. he fa o&s C&rtis0Shapley %e+ate in 1:(@ concerne% which f&n%a ental astrono ical&estion in astrono y?

A) Whether all stars were like the S&n or f&n%a entally %ifferentB) Whether the spiral 5ne+&lae6 were part of the Milky Way #ala*y or ore %istant=

separate entitiesC) Whether the &ni-erse was e*pan%in, o&twar% in all %irections") Whether the S&n was at the center of the Milky Way #ala*y

Ans$ BSection$ 1'01

>. he e-ent that settle% the Shapley0C&rtis %e+ate a+o&t 5spiral ne+&lae6 wasA) 7%win !&++le eas&rin, the %istance to the An%ro e%a #ala*y.B) Arno


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A) perio% of +ri,htness -ariation an% spectral color.B) -ariation of spectral color an% %istance to the star.C) perio% of +ri,htness -ariation an% l& inosity.") a plit&%e of +ri,htness -ariation an% l& inosity.

Ans$ C

Section$ 1'01

1>.In %eter inin, the %istance to a ,ala*y +y &sin, o+ser-ations of a Cephei% -aria+le star=which of the followin, is NE nee%e%?

A) he starFs a-era,e +ri,htness or apparent a,nit&%eB) he starFs -elocity -ia the "oppler effectC) he type of spectr& of the Cephei%= i.e.= whether it is etal0rich or etal0poor ") he Cephei%Fs perio% of -aria+ility

Ans$ BSection$ 1'01 an% ool+o* 1'01

1:.A Cephei% -aria+le star with a p&lsation perio% of a few %ays is seen in the spiral ar of a,ala*y. Its apparent +ri,htness is eas&re% as 1@ 9 ti es fainter than an e &i-alent star1@@@ ly away fro the S&n in o&r #ala*y. Ass& in, no li,ht a+sorption +etween,ala*ies= what is the %istance to the far Cephei% an% hence to the ,ala*y?

A) 1@; ly 41@9 ti es farther away) C) 1@ ly 41@@ ti es closer)B) 1@=@@@ ly 41@ ti es farther away) ") 1@@=@@@ ly 41@@ ti es farther away)

Ans$ "Section$ 110 an% 1'01

(@.A classical Cephei% -aria+le star is seen to -ary re,&larly with a perio% of (' %ays. !owany ti es +ri,hter than the S&n wo&l% this star appear to +e if it were to replace the S&n

in o&r solar syste ? 4See Di,&re 1'09 of Co ins an% Ka&f ann= Discovering theUniverse = ;th 7%.)A) 1@@@ B) 9 C) 1@=@@@ ") 1@(

Ans$ CSection$ 1'01 an% Di,&re 1'09

(1.A classical Cephei% -aria+le star in a %istant ,ala*y has an apparent a,nit&%e of G(@. .By eas&rin, its perio% an% &sin, the perio%0l& inosity relation= its a+sol&te a,nit&%eis H .@. Ass& in, that there is no interstellar a+sorption= what is the %istance to the,ala*y in parsecs? 4See ool+o* 1'01 of Co ins an% Ka&f ann= Discovering theUniverse = ;th 7%.)A) . 1@9 pc B) ;.( 1@ pc C) 1.1 1@ ' pc ") 1.> 1@ pcAns$ "Section$ 1'01 an% ool+o* 1'01

((.!ow has the a*i & intrinsic +ri,htness 4 ini & a+sol&te a,nit&%e) of ype Ias&perno-ae +een eas&re%?

A) he %istances to near+y ype Ia s&perno-ae ha-e +een eas&re% &sin,tri,ono etric paralla*.

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B) hey ha-e +een o+ser-e% in %istant ,ala*ies in which Cephei% -aria+les ha-e also +een o+ser-e%.

C) heir +ri,htness has +een eas&re% at se-eral %ifferent wa-elen,ths= fro whichtheir te perat&re an% hence their intrinsic +ri,htness can +e calc&late%.

") he +ri,htness of se-eral of the has +een acc&rately eas&re% relati-e to the

+ri,htness of the ori,inal star +efore it e*plo%e%.Ans$ BSection$ 1'01

( ."eter ination of the %istance to the An%ro e%a 5ne+&la6 4which finally resol-e% theC&rtis0Shapley %e+ate on the nat&re of 5spiral ne+&lae6) was carrie% o&t +y !&++le +yo+ser-in,

A) p&lsars.B) Cephei% -aria+le stars.C) the "oppler shift of stars in the ne+&la.") the ain se &ence of stars in the 5ne+&la.6

Ans$ BSection$ 1'01

(9.!ow far away fro &s is the An%ro e%a #ala*y co pare% to the %ia eter of the MilkyWay #ala*y?

A) It is a+o&t three Milky Way %ia eters away.B) It is a+o&t (@ Milky Way %ia eters away.C) It is +etween 1@@ an% 1(@ Milky Way %ia eters away.") It is se-eral illion Milky Way %ia eters away.

Ans$ BSection$ 1'01

('. he o+ser-ation +y !&++le that %e onstrate% for the first ti e that the An%ro e%a5ne+&la6 was at a -ery lar,e %istance fro the S&n= an% o&tsi%e o&r #ala*y= was

A) that Cephei% -aria+le stars appeare% to +e -ery faint in the 5ne+&la.6B) that the 5ne+&la6 appeare% to +e rotatin, ni,ht +y ni,ht aro&n% a center that was

not the center of o&r #ala*y.C) that stars with characteristics si ilar to those of o&r S&n appeare% to +e a+sent in

this 5ne+&la.6") that ,lo+&lar cl&sters appeare% to +e %istri+&te% in a halo aro&n% the 5ne+&la=6 a

s&re si,n of a separate ,ala*y.Ans$ ASection$ 1'01

( .What was the i plication of the o+ser-ation +y 7%win !&++le that the Cephei% -aria+lestars he eas&re% in the An%ro e%a 5ne+&la6 appeare% to +e -ery faint co pare% withwhat was e*pecte%?

A) he o+ser-e% perio% was affecte% +y the intense ,ra-itational fiel% of the 5ne+&la6as pre%icte% +y ,eneral relati-ity= lea%in, to incorrect l& inosity %eter ination.

B) he An%ro e%a 5ne+&la6 was -ery far away an% was in fact a ,ala*y.

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C) !e ha% %isco-ere% a new class of intrinsically faint Cephei% -aria+le stars.") "&st an% ,as in the 5ne+&la6 ha% se-erely re%&ce% the li,ht fro these stars.

Ans$ BSection$ 1'01

(;. he etho% &se% +y !&++le to %eter ine the %istance to the An%ro e%a #ala*y 4M 1)=there+y esta+lishin, the concept of separate an% in%i-i%&al ,ala*ies thro&,ho&t the&ni-erse= was the

A) o+ser-ation of Cephei% -aria+le stars.B) eas&re ent of the re%shift of the whole ,ala*y.C) eas&re ent of stellar paralla*= or apparent otion= of stars +eca&se of the 7arthFs

or+ital otion.") o+ser-ation of the +ri,htnesses of no-as.

Ans$ ASection$ 1'01

(>. he An%ro e%a #ala*y 4M 1) is +est %escri+e% asA) an e*tension of the Milky Way.B) a -orte* s&rro&n%in, a +lack hole.C) a ,aseo&s ne+&la= e*ten%in, for across o&r sky.") a spiral collection of stars= %&st= an% ,as= ( illion ly away.

Ans$ "Section$ 1'01

(:.What is it that akes the st&%y of the str&ct&re of o&r own #ala*y ore %iffic&lt than thatof &ch ore %istant spiral ,ala*ies?

A) he ,alactic center is -isi+le only fro the so&thern he isphere= where= &ntilrecently= no a or telescopes were a-aila+le for the st&%y of ,alactic str&ct&re.

B) E&r #ala*y appears to +e &ni &e= with a str&ct&re &ite &nlike any other ,ala*y.C) E&r star is within the #ala*y= an% its otion conf&ses the interpretation of the

otion of other parts of the #ala*y.") Most of o&r ,ala*y is hi%%en +ehin% %ense ,as an% %&st clo&%s in the ,alactic

plane.Ans$ "Section$ 1'01

@.In the 1;>@s= Sir Willia !erschel trie% to eas&re the S&nFs position in o&r #ala*y +yA) co&ntin, the %ensity of stars in %ifferent %irections alon, the Milky Way.B) eas&rin, %istances to star cl&sters an% ! II re,ions in the %isk of the #ala*y.C) eas&rin, the locations of ,lo+&lar cl&sters aro&n% the #ala*y.") co parin, o&r #ala*y to photo,raphs of the An%ro e%a #ala*y.

Ans$ ASection$ 1'0(

1. he factor that isle% !erschel into concl&%in, that the stars of the Milky Way were%istri+&te% with the S&n at the center of the #ala*y was

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A) hot hy%ro,en ,as in the #ala*y= its e ission hi%in, the ore %istant stars.B) interstellar %&st that o+sc&re% the ore %istant stars an% there+y locali e% his

o+ser-ations.C) ,ra-itational +en%in, of li,ht +y the ass of the #ala*y= %istortin, the relati-e

positions of the stars.

") that ost of the 5stars6 he eas&re% were in fact %istant ,ala*ies that are%istri+&te% &nifor ly aro&n% the S&n.Ans$ BSection$ 1'0(

(.Why are we a+le to see only a relati-ely s all part of o&r #ala*y= the Milky Way#ala*y?

A) here are so any stars in o&r #ala*y that the ore %istant ones are hi%%en +ehin%the nearer ones.

B) "istant stars are o+sc&re% +y ,as in interstellar space.C) 7*pansion of the &ni-erse has carrie% the ore %istant stars o&t of o&r -iew.

") "istant stars are o+sc&re% +y %&st in interstellar space.Ans$ "Section$ 1'0(

.In the ei,hteenth cent&ry= Sir Willia !erschel &se% star co&nts in %ifferent re,ions of thesky alon, the Milky Way to esti ate the position of the center of the Milky Way. !eincorrectly concl&%e% that the S&n was close to that center. he reason for this erroneo&sconcl&sion was

A) that the re%shift of the ore %istant stars a%e the in-isi+le to !erschel.B) that !erschel co&nte% all 5stars6 in each star fiel% an% incl&%e% any ,ala*ies that

were o&tsi%e o&r #ala*y= th&s conf&sin, the %istri+&tion.C) the lar,e &antity of a+sor+in, %&st +etween stars= which o+sc&re% the ore %istant

re,ions of the #ala*y.") that e issions fro hot hy%ro,en ,as clo&%s ser-e% to hi%e the ore %istant stars=

locali in, his search.Ans$ CSection$ 1'0(

9.Interstellar %&st o+sc&res o&r -iew of %istant re,ions of space at optical wa-elen,ths. Inthis re,ar%= which of the followin, state ents is tr&e?

A) he o+sc&ration is -ery cl& py an% ran%o o-er the whole sky= the in%i-i%&ala+sor+in, %&st clo&%s showin, no preference for one partic&lar %irection or plane.

B) he o+sc&ration is ro&,hly &nifor o-er the whole sky.C) he o+sc&ration is the least in the plane of the #ala*y an% is stron,est when we

look o&t into the ,alactic halo= at ri,ht an,les in this plane.") he o+sc&ration is se-ere only in the plane of the #ala*y.

Ans$ "Section$ 1'0(

'.Which co ponent of o&r #ala*y acco&nts for interstellar e*tinction= the %i in, of li,ht

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fro %istant o+ ects?A) Cool hy%ro,en ,asB) he so0calle% hi%%en or issin, atter since its a+sor+in, properties ren%er it

in-isi+le in the #ala*yC) Molec&les s&ch as ! ( an% CE= which are stron, a+sor+ers= in olec&lar clo&%s

") "&stAns$ "Section$ 1'0(

. he one co ponent of the aterial of the Milky Way #ala*y that pre-ents &s fro seein,an% photo,raphin, the ,alactic center at optical wa-elen,ths is

A) -ery col% hy%ro,en ,as. C) the ,lare of li,ht fro near+y stars.B) interstellar %&st. ") hot hy%ro,en ,as.

Ans$ BSection$ 1'0(

;.What &sef&l p&rpose %i% -aria+le stars ser-e for !arlow Shapley in locatin, the ,alacticcenter?A) hey are i portant spiral ar tracers an% th&s %efine% the shape of the #ala*y.B) heir +ri,htness -ariations allowe% acc&rate %istances to +e eas&re%.C) hey e it copio&s a o&nts of infrare% ra%iation an% are th&s -isi+le thro&,h

interstellar %&st that o+sc&res -isi+le li,ht.") hey are concentrate% in the ,alactic center an% so %efine% its %irection.

Ans$ BSection$ 1(01 an% 1'0(

>. he etho% &se% +y !arlow Shapley in 1:1; to esti ate the S&nFs location in o&r #ala*ywas the eas&re ent of

A) the locations of ,lo+&lar cl&sters aro&n% the #ala*y.B) the %ensity of stars in %ifferent %irections alon, the Milky Way.C) %istances to open star cl&sters an% ! II re,ions in the %isk of the #ala*y.") the str&ct&re of the An%ro e%a #ala*y an% a co parison of this to the str&ct&re of

o&r #ala*y.Ans$ ASection$ 1'0(

:.!arlow Shapley first locate% the center of o&r #ala*y in 1:1; +yA) eas&rin, the positions of s&perno-a e*plosions thro&,ho&t the #ala*y.B) o+ser-in, the %istri+&tion of ,lo+&lar cl&sters in the ,alactic halo.C) re%shift eas&re ents on stars in the ,alactic plane an% %isk.") o+ser-in, the %istri+&tion of hy%ro,en ,as= eas&re% +y (10c ra%io e ission.

Ans$ BSection$ 1'0(

[email protected] %istances were caref&lly eas&re% fro the 7arth to ,lo+&lar cl&sters a+o-e an% +elow the Milky Way plane 4where o&r -iew of the is not o+sc&re% +y interstellar %&st

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an% ,as)= their %istri+&tion was fo&n% to +eA) spherically sy etric a+o&t a point in the constellation Sa,ittari&s an%

concentrate% in that %irection.B) in a relati-ely flat %isk al ost perpen%ic&lar to the plane of the #ala*y= with a

relati-ely hi,her %ensity of cl&sters towar% its center.

C) concentrate% in the plane of the Milky Way an% cl&stere% aro&n% the S&nFs position=in%icatin, that the S&n is close to the #ala*yFs center.") &nifor ly %istri+&te% thro&,ho&t space= with no concentration in any area of the

Milky Way.Ans$ ASection$ 1'0(

91.!arlow ShapleyFs ori,inal esti ate of the %istance fro the S&n to the ,alactic center wasincorrect +eca&se it %i% not take scatterin, +y interstellar %&st into acco&nt. his ori,inalesti ate was

A) too lar,e +eca&se li,ht scatterin, an% a+sorption +y %&st a%e nearer stars look %i

as tho&,h they were ore %istant.B) too lar,e +eca&se scatterin, +y %&st a%e stars look re%%er as tho&,h they werehi,hly "oppler shifte% an% th&s ore %istant.

C) too s all +eca&se ,as an% %&st ten% to reflect li,ht +ack into the path of the +ea =th&s akin, stars look +ri,hter an% nearer.

") too lar,e +eca&se scatterin, +y %&st a%e stars look re%%er as tho&,h they werere% ,iants of lar,er l& inosity an% th&s farther away.

Ans$ ASection$ 1'0(

9(.In which constellation in o&r sky is the center of o&r Milky Way #ala*y locate%?A) Sa,ittari&s B) 2yra C) !erc&les ") 8rsa Ma or Ans$ ASection$ 1'0(

9 .3a%io wa-es of (10c wa-elen,th ori,inate fro which co ponent of the interstellare%i& ?

A) Cool= ne&tral ato ic hy%ro,en C) Cool= car+on ono*i%e= CEB) Col%= olec&lar hy%ro,en= ! ( ") !ot= ioni e% ato ic hy%ro,en

Ans$ ASection$ 1'0(

99. he spiral0ar str&ct&re of the Milky Way #ala*y has +een eas&re% an% e-al&ate% osteffecti-ely +y o+ser-ations of

A) ,lo+&lar cl&sters in the halo of the #ala*y.B) Bal er e ission lines of -isi+le ra%iation fro hy%ro,en.C) (10c ra%iation fro interstellar hy%ro,en an% the %istri+&tion of yo&n, stars.") 2y an 8 ra%iation fro hot hy%ro,en ,as.

Ans$ CSection$ 1'0(

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9'.Which type of ra%iation has +een ost effecti-e in e-al&atin, the spiral ar str&ct&re ofo&r #ala*y?

A) (10c ra%io e ission fro electron 5spin0flip6 transitions in cool hy%ro,en ,asB) 2y an &ltra-iolet e ission fro hot hy%ro,en ,as

C) Synchrotron ra%iation fro electrons spiralin, in a,netic fiel%s within the spiralar s") Ne&trinos fro e*plo%in, stars in the spiral ar s since they can penetrate %&st an%

,as easilyAns$ ASection$ 1'0(

9 .What happens when the electron in a hy%ro,en ato flips its %irection of spin= fro parallel to antiparallel to that of the proton?

A) Nothin, this is a for+i%%en transition that ne-er occ&rs.B) he ato e its a photon of ' . 0n wa-elen,th 4! ) in the re% re,ion of the

spectr& .C) he ato e its a photon of (10c wa-elen,th in the ra%io re,ion of the spectr& .") he ato e its a photon of 1(1.'0n wa-elen,th 42 ) in the 8 re,ion of the

spectr& .Ans$ CSection$ 1'0(

9;.What wo&l% yo& e*pect to +e the o-erall color of a ,lo+&lar cl&ster of stars= an% why?A) Bl&e= +eca&se of the contri+&tion fro yo&n, an% -ery hot stars in the cl&ster B) 3e%= +eca&se of the e ission of li,ht +y the hy%ro,en ,as in ! II re,ions

s&rro&n%in, the stars in the cl&ster

C) 3e%= +eca&se of the ol%er pop&lation of stars in the cl&ster ") Bl&e= +eca&se of the scatterin, of starli,ht fro the %&st s&rro&n%in, the stars in

the cl&ster Ans$ CSection$ 1(011 an% 1'0(

9>.Where are any of the ol%er= etal0poor stars fo&n% in the Milky Way #ala*y?A) hro&,ho&t the whole #ala*y C) In the %isk an% spiral ar sB) At the ,alactic center ") In ,lo+&lar cl&sters in the ,alactic halo

Ans$ "Section$ 1(011 an% 1'0(

9:.What ato ic transition occ&rs in the ato s of hy%ro,en ,as in the spiral ar s of o&r#ala*y to pro%&ce the (10c ra%io e ission?

A) he transition fro the n L ( to n L 1 le-els in ato ic hy%ro,enB) he chan,e in rotation of the olec&le ! ( a+o&t an a*is perpen%ic&lar to the

olec&lar a*isC) he chan,e in the -i+rational state of the ! ato s in the ! ( olec&le") he in-ersion of the electron spin relati-e to the proton spin= fro parallel to

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antiparallelAns$ "Section$ 1'0

'@.What &ant& transition occ&rs insi%e a hy%ro,en ato to pro%&ce a (10c ra%io

photon?A) An electron falls fro the le-el n L 1@@ to the le-el n L :: in the ato .B) An electron in the ,ro&n% ato ic state re-erses its %irection of spin with respect to

that of the proton.C) An electron re-erses the %irection of its otion in or+it aro&n% the proton.") he electron co +ines with the proton in the n&cle&s to +eco e a ne&tron=

pro%&cin, ener,y.Ans$ BSection$ 1'0

'1. he a or a%-anta,es of the (10c ra%io e ission fro hy%ro,en ,as for in-esti,atin,

the spiral str&ct&re of o&r #ala*y areA) that it is relati-ely easily a+sor+e% +y hy%ro,en ,as in the Milky Way= so thateas&re ents are not conf&se% +y e ission of this ra%iation fro other ,ala*ies

+eyon% the Milky Way. It ori,inates only fro col% hy%ro,en ,as an% can +e &se%to ap this i portant co ponent.

B) that ra%io wa-es easily penetrate the Milky Way %&st an% ,as= an% it is a -erynarrow0wa-elen,th line e ission= th&s its "oppler shift can +e &se% to eas&re ,as

otions.C) that "oppler shift of this narrow0wa-elen,th line e ission is ca&se% +y the

te perat&re of the hot hy%ro,en ,as an% therefore can +e &se% to eas&re the%istri+&tion an% te perat&re of this i portant co ponent of the Milky Way.

") that this e ission can easily penetrate the Milky Way ,as an% %&st an% co es onlyfro hot ,as= hence its a+ility to +e &se% to ap the %istri+&tion of hot hy%ro,en,as.

Ans$ BSection$ 1'0

'(.A ne&tral hy%ro,en ato consists of a proton an% an electron. he ener,y of the ato isA) the sa e re,ar%less of the relati-e spin orientations of the two particles.B) hi,hest when the proton spin an% the electron spin are perpen%ic&lar to each other.C) hi,hest when the two spin %irections are parallel.") hi,hest when the two spin %irections are anti0parallel.

Ans$ CSection$ 1'0

' .If we ai a ra%io telescope at a %istant spiral ar of o&r #ala*y= we will pro+a+lyo+ser-e a (10centi eter line. If we point a lar,e optical telescope at this sa e re,ion= wewill pro+a+ly not +e a+le to %etect the ne&tral hy%ro,en that ,i-es rise to the (10centi eter ra%io si,nal. Why not?

A) Ne&tral hy%ro,en is incapa+le of e ittin, -isi+le ra%iation.

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B) he ! line the pri ary e ission of ne&tral hy%ro,en has a &ch s allerener,y than the (10centi eter ra%io wa-e an% th&s is har%er to %etect.

C) here is little ener,y in the %epths of space to e*cite -isi+le ra%iation fro ne&tralhy%ro,en.

") he -isi+le li,ht e itte% +y ne&tral hy%ro,en is all a+sor+e% +y ! II ,as re,ions

+efore reachin, the solar syste .Ans$ CSection$ 1'0

'9.We ai o&r ra%io telescope at a %istant re,ion of o&r #ala*y an% %etect (10centi eterra%io wa-es with no "oppler shift. 7ach of the followin, is a possi+le e*planation=except one . Which is the e*ception?

A) he ne&tral hy%ro,en in this re,ion is not o-in, relati-e to the 7arth.B) he ne&tral hy%ro,en in this re,ion is o-in, perpen%ic&larly across o&r line of

si,ht.C) he ne&tral hy%ro,en in this re,ion is in a circ&lar or+it aro&n% the ,alactic center

at the sa e ra%i&s as the solar syste .") he ne&tral hy%ro,en in this re,ion is o-in, away fro &s instea% of towar% &s.Ans$ "Section$ 1'0

''.When we eas&re the narrow line e issions of hy%ro,en at (10c ra%io wa-elen,thsalon, a partic&lar line of si,ht thro&,h the %isk of o&r #ala*y= we can tell the %istances to%ifferent hy%ro,en clo&%s +eca&se

A) a+sorption of e*tra,alactic ra%iation at this wa-elen,th will +e ,reater the fartheraway the a+sor+er is fro the S&n.

B) clo&%s that are farther away ha-e s aller an,&lar si es.

C) the e ission is weaker fro clo&%s that are farther away.") clo&%s at %ifferent %istances ha-e %ifferent "oppler shifts +eca&se of the rotation of the #ala*y.

Ans$ "Section$ 1'0

' . he (10centi eter line is one of the ost i portant wa-elen,ths in ra%io astrono y. hefact that it is a relati-ely lon, wa-elen,th is i portant +eca&se

A) lon, wa-elen,ths are ore likely to interact with clo&%s of ,as an% %&st.B) lon, wa-elen,ths are ore likely to pass thro&,h clo&%s of ,as an% %&st.C) lon, wa-elen,ths carry ore ener,y than short wa-elen,ths of the sa e ener,y.

") lon, wa-elen,ths can +e %etecte% with ,reater resol&tion than can shortwa-elen,ths.Ans$ BSection$ 1'0

';.Which of the followin, co ponents of the #ala*y +est o&tline the spiral ar s of the#ala*y?

A) o&n, E an% B stars= %&st= an% ,as C)


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B) #lo+&lar cl&sters ") White %warf starsAns$ ASection$ 1'0

'>.Where are +ri,ht= yo&n, E an% B stars ost likely to +e fo&n% in o&r #ala*y?

A) Insi%e spiral ar sB) In ,lo+&lar cl&stersC) In the o&ter ost re,ions of the %isk= where &ch of the 5%ark atter6 is locate%") Between spiral ar s= where there is less a+sor+in, aterial

Ans$ ASection$ 1'0

':. he stellar co ponents of the #ala*y that act as tracers for the appin, of spiral arstr&ct&re in the Milky Way are

A) +ri,ht= pop&lation I stars an% e ission ne+&lae s&rro&n%in, the .B) ,lo+&lar cl&sters.

C) s&perno-a e*plosions since they are -ery l& ino&s an% can +e seen thro&,hconsi%era+le %&st an% ,as.") ol%= re% ,iant stars an% white %warfs.

Ans$ ASection$ 1'0

@.Which of the followin, is NE &sef&l for appin, the locations an% shapes of the spiralar s of o&r #ala*y?

A) he %istri+&tion of ,lo+&lar cl&stersB) he %istri+&tion of E an% B starsC) he %istri+&tion of e ission ne+&lae 4! II re,ions)") he %istri+&tions of ,iant olec&lar clo&%s

Ans$ ASection$ 1'0

1.What is the %istri+&tion of ,iant olec&lar clo&%s in o&r #ala*y an% other si ilar,ala*ies?

A) hey occ&r pri arily in the spiral ar s.B) hey are %istri+&te% &nifor ly thro&,ho&t the %isk.C) hey are concentrate% close to the ,alactic center.") hey are %istri+&te% thro&,ho&t the halo= with ,reater %ensity towar% the center.

Ans$ ASection$ 1'0

(.When we look o&t into the plane of the #ala*y= how far can we see?A) Infinitely far C) 2ess than 1@@@ lyB) A+o&t 1@@=@@@ ly ") A+o&t 1@=@@@ ly

Ans$ "Section$ 1'0

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.3ecent o+ser-ations see to in%icate that= rather than +ein, a spiral ,ala*y= the MilkyWay ay +e

A) a +arre% spiral with a %efinite= strai,ht +ar across its center.B) an irre,&lar ,ala*y with chaotic %istri+&tion of atter within it.C) an elliptical ,ala*y with little str&ct&re.

") two elliptical ,ala*ies colli%in, with each other= in -iew of the -ery acti-e starfor ation within the ,alactic plane= +ro&,ht a+o&t +y the -astly increase% %ensity%&rin, the collision.

Ans$ ASection$ 1'0

9. he %i ensions of the %isk of o&r Milky Way #ala*y areA) %ia eter 1@@=@@@ ly/ thickness (@@@ ly.B) %ia eter 1@=@@@ ly/ thickness (>=@@@ ly.C) %ia eter (@@@ ly/ thickness 1@@=@@@ ly.") %ia eter (>=@@@ ly/ thickness (@@@ ly.

Ans$ ASection$ 1'0

'. he ratio of thickness to %ia eter of the Milky Way #ala*y isA) 1 '@@. B) 1 '. C) 1 '@. ") 1 1@@@.Ans$ CSection$ 1'0

. he %ia eter of o&r #ala*y is a+o&tA) 1@@ kpc. B) 1 kpc. C) .1 kpc. ") ( kpc.Ans$ BSection$ 1'0

;.Interstellar atter o+sc&res o&r -iew of the %isk of o&r #ala*yA) ost at ra%io wa-elen,ths= where hy%ro,en a+sor+s ra%io wa-es efficiently= an%

least at optical wa-elen,ths.B) ore at optical wa-elen,ths an% less or not at all at infrare% an% ra%io wa-elen,ths.C) -ery little at any wa-elen,th.") ore or less e &ally at all wa-elen,ths= fro ra%io wa-es to li,ht wa-es.

Ans$ BSection$ 1'0

>.!ow is cool= ne&tral hy%ro,en ,as= ! I= %etecte% in the spiral ar s of ,ala*ies?A) By the a+sorption of infrare% ra%iation fro e*tra,alactic so&rcesB) By its Bal er line e issionsC) By its (10c line ra%io e issions") By its &ltra-iolet= 2y an = hy%ro,en line e issions

Ans$ CSection$ 1'0

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;9. he S&nFs position in the #ala*y isA) &nknown +eca&se o&r -iew is too se-erely restricte% +y interstellar %&st.B) in the %isk of the #ala*y= insi%e a spiral ar or se, ent of a spiral ar .C) in the %isk of the #ala*y= +etween an% well away fro any spiral ar .

") in the spherical halo= so ewhat a+o-e an% o&tsi%e of the spiral ar s.Ans$ BSection$ 1'0

;'.Appro*i ately how far is the S&n fro the center of o&r #ala*y?A) ( kpc B) > kpc C) 9: kpc ") 1 @ kpcAns$ BSection$ 1'0

; .A ap of o&r #ala*y %e%&ce% fro ra%io o+ser-ations of the (10c line e ission frocool hy%ro,en ,as an% o+ser-ations of spiral ar tracers s&ch as ,iant olec&lar clo&%s

re-ealsA) two spiral ar s= one on each si%e of the #ala*y.B) a s ooth %istri+&tion of stars= characteristic of an elliptical ,ala*y.C) at least fo&r spiral ar s.") one spiral ar that wraps aro&n% the #ala*y se-eral ti es.

Ans$ CSection$ 1'0

;;. he Milky Way #ala*y appears to ha-e a spiral str&ct&re withA) fo&r separate a or ar s.B) three loosely wo&n% ar s.C) one 5ar 6 wo&n% aro&n% the n&cle&s fo&r ti es.") two a or ar s wo&n% twice aro&n% the n&cle&s.

Ans$ ASection$ 1'0

;>.Where is the S&n locate% in o&r #ala*y? 4 hat is= what is o&r a%%ress in the &ni-erse?)4See Di,. 1'0: of Co ins an% Ka&f ann= Discovering the Universe = ;th 7%.)

A) In the Centa&r&s ar = +etween the ,alactic center an% the Erion arB) In the Sa,ittari&s ar = +etween the Centa&r&s an% Erion ar sC) In the


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away.C) a+o&t twice as +ri,ht as at present since nei,h+orin, stars wo&l% +e ostly +ri,ht=

yo&n, +l&e stars in a+o&t the sa e n& +ers as the present= ol%er= an% less +ri,htre% ,iant nei,h+ors to the S&n.

") e*tre ely intense fro the %ense fiel% of stars= e &i-alent to a+o&t (@@ f&ll Moons.

Ans$ "Section$ 1'09

>@.Which kin% of stars are the a or so&rce of ener,y for the heatin, of the %&st clo&%s an%the ! II e ission ne+&lae within the planes of the Milky Way an% other ,ala*ies?

A) !ot= yo&n, E an% B stars= -ia their 8 ra%iationB) he n& ero&s ol%= re% ,iant K an% M stars= -ia their I3 heat ra%iationC) ery hot white %warf stars= the re nants of planetary ne+&las in the ,as clo&%s") he -ery any no-a an% s&perno-a e*plosions of stars within the ,as an% %&st

clo&%sAns$ A

Section$ 1'09>1.We ha-e o+ser-e% the central re,ion of the Milky Way #ala*y in a n& +er of wa-elen,th

ran,es. With which one of these is it ost %iffic&lt to o+tain infor ation?A) Infrare% B) 3a%io C) isi+le ") #a a rayAns$ CSection$ 1'09

>(.Ene c&rio&s fact a+o&t the Milky Way #ala*y= %isco-ere% in the past few years= is thatA) a si,nificant fraction of its ass is in the for of ,lo+&lar cl&sters= %istri+&te% in a

spherical halo centere% on the ,alactic center.B) a lar,e +lack hole is slowly clearin, o&t the ass near the ,alactic center= lea-in, a

col%= %ark -oi%.C) enor o&s a o&nts of ener,y are po&rin, o&t of a co pact +&t -ery assi-e so&rce

at its center.") the a ority of its ass is within the spiral ar s e*ten%in, o&t into space.

Ans$ CSection$ 1'09

> .What is the si,nificance of the o+ ect Sa,ittari&s AO 45Sa,ittari&s A0star6) in o&r #ala*y?A) It appears to +e a et of aterial e ecte% fro an accretion %isk aro&n% a

s&per assi-e +lack hole in the ,alactic n&cle&s.B) It is a ,lo+&lar cl&ster passin, close to the ,alactic n&cle&s= an% the 33 2yrae stars

in it allow the %istance to the ,alactic center to +e calc&late%.C) It is a +ri,ht= hi,h0spee% clo&% of ,as close to the ,alactic n&cle&s that allows the

ass of the n&cle&s to +e calc&late%.") It appears to +e the act&al n&cle&s of the #ala*y.

Ans$ "Section$ 1'09

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>9.;.What e-i%ence now e*ists for a s&per assi-e +lack hole at the center of o&r #ala*y?A) ery +ri,ht P0ray e issions fro the ,alactic center B) E+ser-ations of intense inflow of atter towar% the center of the #ala*y as seen +y

li,ht= "oppler0shifte% towar% the re%= e itte% +y this atter C) ery rapi% otion of atter close to the n&cle&s of the #ala*y= re &irin, a -ery

assi-e +o%y to hol% it in or+it") A -ery %ark -oi% in an otherwise +ri,ht re,ion of space near the ,alactic center=

in%icatin, the presence of a +lack holeAns$ CSection$ 1'09

>>.What is the e-i%ence that in%icates to so e astrono ers that a s&per assi-e +lack holee*ists at the center of o&r #ala*y?

A) "oppler shift of li,ht fro stars in the near nei,h+orhoo% of the ,alactic centerin%icates that the stars are fallin, inwar% at -ery hi,h spee%s.

B) he S&nFs otion in space shows that= if KeplerFs law hol%s for its or+it aro&n% the,alactic center= there M8S +e a -ery assi-e o+ ect at this center.

C) No electro a,netic ra%iation at all co es fro the precise position of the ,alacticcenter= an% it &st looks like a %ark -oi% in space.

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: . he star S( or+its Sa,ittari&s AO 4the ,alactic center) with a perio% of 1'.( years an% ase i a or a*is of :'@ A8. What %oes KeplerFs thir% law s&,,est as the total a o&nt of

ass insi%e the or+ital ra%i&s of S(?A) 1. 1@ M . B) (. 1@ M . C) .; 1@ M . ") :.9 1@ : M .

Ans$ CSection$ 1'09 an% ool+o* 1109

:9.If the +lack hole in the center of the #ala*y has a ass of 9 1@ solar asses= whatwo&l% +e its ra%i&s 4that is= the ra%i&s of its e-ent hori on)?

A) 1.( 1@ ; 4a+o&t twice the ra%i&s of the 7arth)B) 1.( 1@ : 4a+o&t twice the ra%i&s of the S&n)C) 1.( 1@ 1@ 4a+o&t one0fifth of Merc&ryFs or+ital ra%i&s)") 1.( 1@ 1( 4al ost twice J&piterFs or+ital ra%i&s)

Ans$ CSection$ 1'09 an% ool+o* 1901

:'.If the +lack hole in the center of the ,ala*y has a ass of 9 1@ solar asses= whatwo&l% +e the or+ital perio% of the 7arth aro&n% this hole in an or+it of ra%i&s 1 A84ass& in, that Newtonian physics an% KeplerFs thir% law apply)?A) 2ess than 1 secon% B) in&tes C) 9Q ho&rs ") ' weeksAns$ CSection$ 1'09 an% ool+o* 1109

: .Where in space wo&l% yo& look for a ,lo+&lar cl&ster?A) In the Milky Way %isk= o-in, in a circ&lar or+it aro&n% the ,alactic center B) Enly in elliptical ,ala*ies since they are co pose% of ol% stars an% %o not e*ist in

yo&n, syste s like spiral ,ala*iesC) In the Milky Way ,alactic halo= or+itin, the ,alactic center in a lon, elliptical or+itaro&n% the ,alactic center

") In the asteroi% +eltAns$ CSection$ 1'0'

:;.What is the ,alactic halo?A) A syste of arcs an% other ,as clo&%s s&rro&n%in, the ,alactic n&cle&sB) A syste of satellite ,ala*ies s&rro&n%in, o&r own Milky Way #ala*yC) A spherical %istri+&tion of stars an% ,lo+&lar cl&sters centere% on the n&clear +&l,e") A lar,e %isk of stars an% olec&lar clo&%s e*ten%in, o&twar% fro the n&clear

+&l,eAns$ CSection$ 1'0'

:>."oes the halo of the Milky Way #ala*y incl&%e other ,ala*ies?A) No= it is not possi+le for one ,ala*y to or+it another ,ala*y.B) No= the halo is li ite% to fiel% stars an% ,lo+&lar cl&sters.

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C) es= the halo re,ion incl&%es the An%ro e%a #ala*y.") es= the halo re,ion incl&%es se-eral s all ,ala*ies= a on, the the Ma,ellanic

Clo&%s= two s all irre,&lar ,ala*ies.Ans$ "Section$ 1'0'

::. he stars in the Milky Way #ala*yA) o+ey !&++leFs law of recession.B) are all rece%in, fro the ,alactic center.C) o-e ,enerally aro&n% the ,alactic center.") n& +er +etween > an% 1@ illion.

Ans$ CSection$ 1'0

1@@. he spee% of the S&n in its or+it aro&n% the #ala*y is %e%&ce% +y reference to an%o+ser-ations of

A) the or+ital otions of stars near the S&n.B) ,lo+&lar cl&sters an% halo stars.C) Cephei% -aria+les= which pro-i%e a %istance stan%ar%.") the ,alactic center= a+o&t which the S&n is or+itin,.

Ans$ BSection$ 1'0

1@1. he ost i portant reason why ,lo+&lar cl&sters are &sef&l for fin%in, the spee% of theS&n in its or+it aro&n% the #ala*y is that

A) ,lo+&lar cl&sters are +ri,ht an% easily seen at lar,e %istances.B) ,lo+&lar cl&sters on a-era,e rotate at the sa e spee% as the S&n aro&n% the center

of the #ala*y.C) ,lo+&lar cl&sters are %istri+&te% &nifor ly aro&n% the #ala*y.") the a-era,e -elocity of all the ,lo+&lar cl&sters &st +e ero if the ,lo+&lars are to

aintain their or+its aro&n% the ,alactic center.Ans$ "Section$ 1'0

1@(.Which of the followin, state ents correctly %escri+es the rotation of o&r #ala*y?A) he %isk rotates like a soli% o+ ect 4o+ ects at all %istances take the sa e ti e to

co plete an or+it)= an% the halo o+ ects ha-e ran%o or+its with no net rotation ofthe halo a+o&t the center of the #ala*y.

B) E+ ects in the %isk ha-e ran%o or+its with no net rotation of the %isk a+o&t thecenter of the #ala*y= an% the halo rotates %ifferentially 4o+ ects farther fro thecenter take lon,er to co plete an or+it than o+ ects closer to the center).

C) he %isk rotates %ifferentially 4o+ ects farther fro the center take lon,er toco plete an or+it than o+ ects closer to the center)= an% the halo rotates%ifferentially 4o+ ects farther fro the center take lon,er to co plete an or+it thano+ ects closer to the center).

") he %isk rotates %ifferentially 4o+ ects farther fro the center take lon,er to

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of the S&nFs spee% of otion aro&n% the center of the #ala*y.B) he "oppler shift sho&l% +e al ost ero for all clo&%s= re,ar%less of %istance.C) he "oppler shift sho&l% rise to a a*i & at so e %istance= then %ecrease a,ain.") he "oppler shift sho&l% +e lar,er the farther away the clo&% is.

Ans$ B

Classification$ CSection$ 1'0

1@>.Which para eter is plotte% as a f&nction of %istance fro the ,alactic center in a rotationc&r-e of a ,ala*y?

A) he ass of atter insi%e the %istance fro the ,alactic center B) he thickness of the ,alactic %isk C) he ass of cool hy%ro,en ,as") he spee% of stars or+itin, the ,alactic center

Ans$ "Section$ 1'0

1@:.!ow %o we o+tain an esti ate of the a o&nt of ass that is insi%e the S&nFs or+ital pathin o&r #ala*y?

A) By co&ntin, stars= ass& in, an a-era,e stellar ass an% calc&latin, the total assB) By o+ser-in, the +en%in, of li,ht fro %istant ,ala*ies as this li,ht passes near the

Milky Way center C) By o+ser-in, the o-e ent of the #ala*y towar% nei,h+orin, ,ala*ies +eca&se of

&t&al ,ra-itational attraction") By applyin, KeplerFs law to the otion of the S&n an% other near+y stars

Ans$ "Section$ 1'0

11@. he present esti ate for the total ass of o&r #ala*y in &nits of solar ass is a+o&tA) (. 1@>. B) 1@1( . C) 1.1 1@11. ") 1@ .Ans$ BSection$ 1'0;

111.M&ch of the ass of o&r #ala*y appears to +e in the for of 5%ark6 atter of &nknownco position. At present= this atter can +e %etecte% only +eca&se

A) it e its synchrotron ra%iation at ra%io wa-elen,ths.B) its ,ra-itational p&ll affects or+ital otions in the #ala*y.C) it +en%s li,ht fro %istant &asars.") it +locks o&t the li,ht fro %istant stars in the plane of o&r #ala*y.

Ans$ BSection$ 1'0;

11(. he presence of a -ery lar,e a o&nt of &nseen 45%ark6) atter in the halo of o&r #ala*yis %e%&ce% fro

A) the rotation c&r-e of o&r #ala*y= in which or+ital spee%s of stars appear to o+eyKeplerFs law.

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B) the rotation c&r-e of o&r #ala*y= in which or+ital spee%s of stars in the o&terre,ions of the #ala*y are si,nificantly hi,her than is pre%icte% +y KeplerFs law inwhich the -al&e for the o+ser-e% ass in the #ala*y is &se%.

C) the &ne*pecte% a+sence of l& ino&s atter 4stars= etc.) +eyon% a certain %istancefro the ,alactic center.

") the hi,h a o&nt of interstellar a+sorption in certain %irections.Ans$ BSection$ 1'0;

11 .A rotation c&r-e is a plot of the rotational -elocity of a ,ala*y as a f&nction of the%istance away fro the ,alactic center.


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11;.What is icrolensin,?A) A in&te shift in the apparent position of a star as an o+ ect passes in front of itB) A slow +ri,htenin, of a star as an o+ ect passes in front of itC) he te porary %isappearance of a star as an o+ ect passes in front of it

") A ,ra%&al re%&ction in +ri,htness of a star as an o+ ect passes in front of itAns$ BSection$ 1'0;

11>.In a recent s&r-ey of stars in the sky= it was fo&n% that occasionally a star that is nor allyof constant +ri,htness will slowly +ri,hten an% then fa%e +ack to its ori,inal +ri,htnessa,ain o-er the space of se-eral weeks. What is +elie-e% to +e the ca&se of this chan,e in

+ri,htness?A) A assi-e coronal e ection on a star with a+nor ally stron, a,netic fiel%sB) he ,ra%&al otion of the star thro&,h a +reak or hole +etween interstellar %&st

clo&%s

C) Microlensin, +y co pact o+ ects s&ch as +rown %warfs passin, in front of the star ") he 5li,htho&se +ea 6 of a slowly rotatin, ne&tron star co panionAns$ CSection$ 1'0;

11:.What physical process has allowe% astrono ers to eas&re the o-erall n& +er an%%istri+&tion of +rown %warfs in o&r #ala*y?

A) heir ,ra-itational fiel%s can +en% the li,ht fro +ack,ro&n% stars.B) hey e it copio&s a o&nts of infrare% ra%iation= which can penetrate the

interstellar e%i& .C) Molec&les in their at ospheres e it ra%io wa-es that can +e %etecte% fro the

7arth.") hey occasionally eclipse 4+lock the li,ht fro ) ore %istant stars.

Ans$ ASection$ 1'0;

1(@.What has icrolensin, tol% &s a+o&t the role of +rown %warfs in the #ala*y?A) hey cannot +e a a or co ponent of the %ark atter in the #ala*y.B) hey are a a or co ponent of the atter that is fallin, into the s&per assi-e

+lack hole in the ,alactic center.C) hey are one of the ost i portant co ponents of the #ala*yFs %ark atter.") It has tol% &s al ost nothin, yet icrolensin, is too %iffic&lt to o+ser-e.

Ans$ ASection$ 1'0;

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