Astronomy - Chapter 12 Test

8/10/2019 Astronomy - Chapter 12 Test

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CHAPTER 12: The Lives of the Stars from Birth through Middle Age

1.Which of the following does NOT happen in a star in the course of its evolution?

A) Build-up of heavy eleents fro fusion of hydrogen

B) !oss of ass as radiation") !oss of ass as atos

#) Build-up of hydrogen fro $rea%-down of heavier eleents $y fission reactions in

its coreAns& #

'ection& (ntroduction to "hapter 1

.The space $etween stars is %nown to contain

A) large *uantities of dust that a$sor$ and scatter light+ $ut no gas+ either atoic or

olecular.

B) varia$le aounts of gas $ut no dust+ which only fors in planetary systes nearstars.

") a perfect vacuu.

#) gas+ $oth atoic and olecular+ and dust.

Ans& #'ection& 1-1

,.Which of the following is NOT an a$undant physical coponent of the interstellar

ediu?

A) Atos and ions B) olecules ") #ust #) adioactive eleentsAns& #

'ection& 1-1

/.Which of the following ethods has NOT yet $een used to study the aterial of theinterstellar ediu?

A) 'cattering of starlightB) "ollection of dust and gas $y spacecraft") 0ission of electroagnetic radiation $y atos and olecules

#) A$sorption of light fro ore distant stars

Ans& B'ection& 1-1

.O$servations of siilar star clusters at different distances fro the 'un show that they

appear to $e fainter than e2pected on the $asis of distance alone. This is $ecauseA) the photons of light $ecoe 3tired4 and appear less $right as they travel.

B) the cosological redshift has oved soe of the light into the infrared spectral

region.") star clusters are systeatically saller+ and hence less $right+ the farther they are

fro the galactic center and hence fro the 'un.

#) light is scattered and a$sor$ed $y interstellar dust and gas $etween distant clustersand the 0arth.

Ans& #

'ection& 1-1

5.(nterstellar e2tinction is

A) the assiilation of interstellar atter $y stars after gravitational attraction and

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capture.

B) the reduction of the apparent $rightness of stars $y scattering and a$sorption of

their light $y intervening interstellar clouds.") the wipe-out of species on the 0arth $y intense radiation fro a near$y supernova.

#) the deaths of high-ass stars in the space $etween other long-lived stars.

Ans& B'ection& 1-1

6.What do a reflection ne$ula surrounding a star and our atosphere have in coon?7eview Guided Discovery: The Color of the Sun fro "hapter /+ "oins and

8aufann+ Discovering the Universe+ 6th 0dition.)

A) They $oth appear $lue $ecause of preferred scattering of this color of light.

B) They $oth have a$out the sae teperature.") They have alost the sae average density of gas.

#) They $oth contain the sae types of olecules.

Ans& A

'ection& 9uided #iscovery& The "olor of the 'un+ "hapter /+ and 1-1

:.The apparent reddening of light fro stars after its passage through the interstellarediu 7(') is caused $y

A) the additional contri$ution to this starlight $y eission fro hydrogen gas in the

('.B) preferential scattering of $lue starlight $y fine dust grains.

") ;eean shift of the light $y the powerful agnetic fields e2isting within the ('.

#) scattering of this light fro rapidly oving aterial+ this light $eing #oppler-

shifted toward the red end of the spectru.Ans& B

'ection& 1-1

<.=ow uch of the visi$le ass of our 9ala2y is in the for of gas and dust spread out

$etween the stars?

A) <> B) !ess than 1 ") > #) 1>Ans& #

'ection& 1-1

1>.What is the ost a$undant eleent in the universe?A) "ar$on B) =eliu ") O2ygen #) =ydrogen

Ans& #

'ection& 1-1

11.What is the second ost a$undant eleent in the universe 7after hydrogen)?

A) =eliu B) "ar$on ") Nitrogen #) (ronAns& A

'ection& 1-1

1.What are the two ost a$undant eleents in the universe?

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A) =ydrogen and car$on ") =ydrogen and heliu

B) =ydrogen and o2ygen #) Nitrogen and o2ygen

Ans& "'ection& 1-1

1,.Which of the following olecules is li%ely to $e the ost coon in interstellar space?A) O=+ hydro2yl ") "O+ car$on ono2ide

B) =+ olecular hydrogen #) =O+ water

Ans& B'ection& 1-1

1/.Which of the following coon olecules found in interstellar space contains nitrogen

atos $ut no o2ygen?A) Water vapor 7=O) ") ethane 7"=/)

B) @oraldehyde 7="O) #) Aonia 7N=,)

Ans& #

'ection& 1-1

1.=ow have cople2 olecules such as foraldehyde 7="O) $een detected in interstellarclouds?

A) By direct sapling $y space pro$es

B) By o$serving the cheical reactions in which they are created") Only $y theoretical odeling since it is %nown that the coponent eleents 7=+ "+

O) are present in space

#) By olecular eission lines

Ans& #'ection& 1-1

15.(n which part of the electroagnetic spectru are olecules ost easily detected?A) isi$le light B) adio waves ") rays #) Cltraviolet light

Ans& B

'ection& 1-1

16.What wavelengths have astronoers used to ap and study the distri$ution of the giant

olecular clouds in space?

A) -ray B) isi$le ") Cltraviolet #) adioAns& #

'ection& 1-1

1:.Which of the following iportant atoic or olecular species is difficult to detect in the

interstellar ediu?

A) olecular hydrogen 7=) ") "ar$on ono2ide 7"O)B) Atoic hydrogen 7=) #) Water vapor 7=O)

Ans& A

'ection& 1-1

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1<.Which of the following easily o$served olecular species is used as a tracer for the

fundaental $ut difficult to o$serve = olecules in giant olecular clouds?

A) =ydro2yl 7O=) ") "ar$on dio2ide 7"O)B) Water vapor 7=O) #) "ar$on ono2ide 7"O)

Ans& #

'ection& 1-1

>.=ydrogen in olecular for+ =+ is thought to $e very a$undant in gas clouds in space+

$ut these olecules eit radiation relatively inefficiently+ since they are syetricalolecules. Which other olecule occurs in close association with = and is used as a

pro$e for olecular clouds?

A) "ar$on ono2ide 7"O) ") Water vapor 7=O)

B) ethane 7"=/) #) "ar$on dio2ide 7"O)Ans& A

'ection& 1-1

1.(n star-foring regions in interstellar space+ which olecule is the easiest to detect?A) Aonia 7N=,) ") @oraldehyde 7="O)

B) =ydrogen 7=) #) "ar$on ono2ide 7"O)Ans& #

'ection& 1-1

.The density of car$on ono2ide is o$served in a particular interstellar cloud to $e >>

"O olecules per cu$ic eter. What will $e the e2pected density of olecular hydrogen

gas+ =+ in this cloud?

A) >> illion olecules of = per cu$ic eter B) >> olecules of = per cu$ic eter

") illion olecules of = per cu$ic eter

#) >+>>> olecules of = per cu$ic eter Ans& "

'ection& 1-1

,.=ow is gas distri$uted in interstellar space?

A) (n clups+ concentrated in interstellar clouds

B) "oncentrated in narrow riverli%e streas of gas that e2tend across the 9ala2y

") Cniforly distri$uted through space#) "oncentrated around e2isting stars $ecause of the starsD gravitational pull

Ans& A

'ection& 1-1

/.What is the typical ass of a giant olecular cloud?

A) 1> to 1>> solar asses ") 1>>+>>> to 1 illion solar assesB) 1>>> to 1>+>>> solar asses #) 1> illion to 1 $illion solar asses

Ans& "

'ection& 1-1

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.What is a typical siEe for a giant olecular cloud?

A) 1>> ly across. ") Anything up to a$out 1 ly across.

B) 1>>> ly across. #) 1> ly across.Ans& A

'ection& 1-1

5.What are the typical diensions of a giant olecular cloud in interstellar space?

A) ass of a$out 1>>> solar asses within a volue with a diaeter of a$out 1>>> ly

B) ass of a$out 1 illion solar asses within a volue with a diaeter of a$out 1>>ly

") ass of a$out 1 illion solar asses within a volue with a diaeter of a$out 1>>

AC+ a$out the siEe of the solar syste

#) ass of a$out 1>>> solar asses within a volue with a diaeter of a$out 1>> lyAns& B

'ection& 1-1

6.9iant olecular clouds+ which are aFor sites of star foration+ can $e up toA) 1> ties the siEe of the solar syste and contain to , solar asses of aterial.

B) 1> pc across and contain a few thousand solar asses of aterial.") 1>> pc across and contain illion solar asses of aterial.

#) 1>>> pc across and contain 1>> illion solar asses of aterial.

Ans& "'ection& 1-1

:.What fraction of the ass of a typical interstellar cloud is hydrogen?

A) B) Alost > ") 6/ #) <:Ans& "

'ection& 1-1

<.What fraction of the ass of a typical interstellar cloud is heliu?

A) > B) ") 1> #)

Ans& #'ection& 1-1

,>.A particular interstellar giant olecular cloud has a ass of +>>>+>>> solar asses.

What is the ass of hydrogen in this cloud?A) />+>>> solar asses ") 1+>>+>>> solar asses

B) 1+>>>+>>> solar asses #) 1+<5>+>>> solar asses

Ans& "'ection& 1-1

,1.A particular giant olecular cloud in interstellar space has a ass of +>>>+>>> solarasses. What is the ass of heliu in this cloud?

A) />+>>> solar asses ") >>+>>> solar asses

B) 1 illion solar asses #) >>+>>> solar asses

Ans& #

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'ection& 1-1

,.What is the characteristic color of a reflection ne$ula?A) ed B) Gellow ") 9reen #) Blue

Ans& #

'ection& 1-1

,,.What causes the characteristic $lue color of a reflection ne$ula?

A) 0lectrons dropping $etween energy levels n H , to n H in hydrogen atosB) 0lectrons dropping $etween energy levels n H to n H 1 in hydrogen atos

") Theral $lac%$ody radiation eitted $y the hot gas

#) 'cattering of starlight fro dust grains in the ne$ula

Ans& #'ection& 1-1

,/.A reflection ne$ula is ade visi$le $y

A) theral energy eitted as a continuous spectru $y the very hot gas+ uch li%ethat eitted $y a hot $ody on the 0arth.

B) light fro e$edded stars reflected over a wide range of wavelengths toward the0arth $y crystals of water+ ethane+ and aonia ices.

") eission lines fro hydrogen+ which itself has $een ioniEed $y C light fro

e$edded stars.#) $lue light preferentially scattered $y dust grains.

Ans& #

'ection& 1-1

,.The distinctive color of a reflection ne$ula is

A) light of all colors+ $ut predoinantly in the red part of the spectru+ eitted $y

cool stars and reflected $y crystals of water ice surrounding the stars.B) several specific colors+ resulting fro fluorescence of atos e2cited $y ultraviolet

radiation eitted $y hot stars.

") $lue+ caused $y the scattering of light fro dust grains.#) red+ resulting fro the eission of light fro hydrogen gas.

Ans& "

'ection& 1-1

,5.The distinct $lue color of the ne$ulosity around stars in young clusters such as the

Ileiades 7see @igure 1-,+ "oins and 8aufann+ Discovering the Universe+ 6th 0d.) is

caused $yA) atos of gas eitting light $y fluorescence+ having $een e2cited $y ultraviolet

radiation fro hot stars.

B) light eitted $y interstellar gases $ut #oppler-shifted $y otion toward theo$server.

") starlight reflected $y $lue-colored interstellar aterial.

#) starlight scattered and reflected $y sall dust grains in the interstellar aterial.

Ans& #

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'ection& 1-1 and @igure 1-,

,6.(n photographs+ the Ileiades open star cluster is surrounded $y a $luish haEe 7see @igure1-,+ "oins and 8aufann+ Discovering the Universe+ 6th 0d.). What causes this $lue

light?

A) 'tarlight scattered fro interstellar dust in the star cluster B) 'tarlight scattered $y the light-sensitive grains in the photographic plate when the

picture was ta%en

") 'hoc% waves losing energy to interstellar gas in the star cluster+ causing the atosto eit light

#) 'tarlight a$sor$ed and re-eitted $y interstellar gas in the star cluster

Ans& A

'ection& 1-1 and @igure 1-,

,:.What is an eission ne$ula 7= (( region)? 'ee @igure 1- in "oins and 8aufann+

Discovering the Universe+ 6th 0d.

A) A region of ioniEed hydrogen around one or ore hot O- and B-type starsB) A region of olecular hydrogen inside a giant olecular cloud

") A region of neutral+ atoic hydrogen in interstellar space#) A region of gas and dust fored $y the e2plosion of a assive star

Ans& A

'ection& 1-1 and @igure 1-

,<.Where are eission ne$ulae 7= (( regions) found?

A) (n or near old open clusters ") (n glo$ular star clusters

B) Around hot stars #) Around low-ass starsAns& B


/>.The $right stars at the center of an eission ne$ula 7= (( region) are

A) young O and B stars. ") hot white dwarfs.

B) red supergiants. #) T Tauri stars.Ans& A


/1.What radiation ioniEes the hydrogen in an eission ne$ula 7= (( region)?A) Cltraviolet radiation fro O and B stars

B) rays fro the coronas of solar-type stars

") (nfrared radiation fro preJain-se*uence stars#) 9aa rays fro neutron stars

Ans& A


/.The energy re*uired to ioniEe the hydrogen gas in an eission ne$ula 7= (( region) coes

fro

A) C eission fro hot O and B stars.

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B) supernovae 7e2ploding stars).

") collisions $etween gas clouds in interstellar space.

#) T Tauri stars.Ans& A


/,.0vidence of assive aounts of hydrogen gas surrounding soe stars coes fro

A) o$servation of the reddening of the spectra of these stars $ecause of a$sorption of

$lue light $y hydrogen.B) o$servation of eission of characteristic red Baler light fro ne$ulosity around

the.

") theoretical calculations that correctly descri$e stellar foration $y the gravitational

contraction of hydrogen gas.#) o$servation of the $lue glow fro scattered light within their reflection ne$ulae.

Ans& B


//.!ong-e2posure color photographs of the night s%y often show regions that glow red+ such

as the osette Ne$ula in @ig. 1-: of "oins and 8aufann+ Discovering the Universe+ 6th 0d. This distinctive red color is caused $y

A) the eission of red and infrared light $y war dust grains.

B) the collective glow of any red giant stars in the region.") the scattering of starlight $y dust grains in the ne$ula.

#) the ioniEation and su$se*uent reco$ination of hydrogen atos.

Ans& #


/.There are several echaniss that can trigger star foration in a cold+ dar% ne$ula. (n

each of these the %ey to star foration isA) to $athe the cold+ dar% ne$ula in ultraviolet radiation and sweep away soe of the

colder aterial.

B) to copress the gas and dust so that gravitation will overcoe the gas pressure.") to heat the gas so that gas pressure will overcoe gravitation.

#) to su$Fect the dar% ne$ula to an intense agnetic field so that supersonic Fets will

for.

Ans& B'ection& 1-

/5.What is the ultiate fate of an open star cluster?A) The shape of the cluster will reain ore or less as it is at the present tie as the

stars in it age and die.

B) The stars in it will escape one $y one until the cluster no longer e2ists.") Over tie the stars will collide and erge+ eventually creating a $lac% hole.

#) The stars will gradually sin% toward the center+ creating a glo$ular cluster.

Ans& B

'ection& 1-

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/6.Which of the following is true a$out open clusters?

A) They will all slowly condense into glo$ular clusters+ the stars having driven off thereaining interstellar dust and gas.

B) One star in an open cluster will eventually undergo a supernova e2plosion that will

*uic%ly disperse the other stars.") As they slowly condense+ their residual rotation will spin the into a flat panca%e

shape and they will $ecoe spiral gala2ies.

#) The otions of individual stars are such that all open clusters will eventuallydisperse.

Ans& #

'ection& 1-

/:.=ow do assive stars norally end their lives?

A) They gradually shrin% to the siEe of the 0arth.

B) We donDt %now since their lifeties are longer than the age of the universe.

") They collapse and $ecoe $lac% holes.#) They e2plode.

Ans& #'ection& 1-

/<.The ost li%ely places where stars and planetary systes are foring in the universe areA) in the centers of gala2ies. ") in regions surrounding *uasars.

B) in ne$ulae coposed of gas and dust. #) in the rarified space $etween gala2ies.

Ans& B

'ection& 1-

>.New stars are fored fro

A) hot supernova renants.B) activity around $lac% holes in the centers of gala2ies.

") huge+ cool dust and gas clouds.

#) pure energy in free space.Ans& "

'ection& 1-

1.=ow does the teperature of an interstellar cloud affect its a$ility to for stars?A) =igher teperatures help star foration.

B) 'tar foration is independent of the teperature of the cloud.

") 'tar foration is too coplicated to $e a$le to say how one *uantity+ such asteperature+ affects it.

#) =igher teperatures inhi$it star foration.

Ans& #'ection& 1-

.What deterines whether a particular region of an interstellar cloud can collapse and

for a star?

Page %




A) Only the teperature since higher teperatures act to prevent collapse

B) The aount of gravity pulling inward copared to gas pressure pushing outward

") The gas density+ the ratio of the ass of the cloud over its volue+ since thisdeterines how gravity will act on the cloud aterial

#) Only the aount of ass in the cloud since this deterines the strength of gravity

Ans& B'ection& 1-

,.What condition is considered sufficient for an interstellar cloud to collapse and for astar or stars 7i.e.+ if this condition holds then the cloud has to collapse)?

A) The cloud ust $e alone in space 7far fro stars and other interstellar clouds).

B) 9ravity ust doinate gas pressure inside the cloud.

") 9ravity ust $e strong enough to reach all parts of the cloud.#) The cloud ust $e cooler than 1>> 8.

Ans& B

'ection& 1-

/.Which of the following echaniss is NOT considered to $e a way in which star

foration is triggered or started?A) "ollisions $etween interstellar clouds

B) =eating of an interstellar cloud $y radiation fro e$edded young stars

") "opression of an interstellar cloud $y the shoc% waves fro supernova e2plosion#) "opression of an interstellar cloud $y the pressure of light fro near$y stars

Ans& B

'ection& 1-

.Which of the following echaniss is NOT thought to $e significant in the foration of

new stars within the interstellar ediu?

A) The heating of an interstellar cloud $y concentrated $eas of neutrinos fronear$y stars

B) The copression of cold interstellar gas $y radiation pressure fro light fro very

$right stars") The condensation of atter $y the shoc% wave fro a near$y supernova

#) The collision of two cold interstellar clouds

Ans& A

'ection& 1-

5.Which of the following echaniss is thought to $e ineffective and inefficient in the

triggering of star $irth in olecular clouds?A) 9ravitational contraction of a hot gas cloud

B) "ollisions $etween two interstellar clouds

") 'upernova e2plosions and the resultant shoc% waves#) adiation pressure fro the intense C radiation fro hot stars

Ans& A

'ection& 1-

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6.The Keans insta$ility descri$es

A) the e2plosion of a star at the end of its life+ the supernova phenoenon.

B) the overcoing of gas pressure $y self-gravity within a cold and dense interstellarcloud to for a star.

") the conditions under which sufficient nu$ers of neutrinos can trigger the collapse

of an interstellar cloud.#) the e2pansion of a gas cloud after gravitational contraction $ecause of $uild-up of

great heat within the cloud fro gravitational potential energy.

Ans& B'ection& 1-

:.What is the typical teperature inside the dense core of a giant olecular cloud that is

collapsing to for a star?A) !ess than 1 8 B) 1> 8 ") 1>>> 8 #) 1>> 8

Ans& B

'ection& 1-

<.The group of stars that is fored when a giant olecular cloud collapses is called

A) an open cluster. B) a gala2y. ") a constellation. #) a gravitational lens.Ans& A

'ection& 1-

5>.Which wavelength region is ost useful for investigating the dense cores inside giant

olecular clouds?

A) (nfrared B) -rays ") Cltraviolet #) Optical

Ans& A'ection& 1-

51.(n which regions of our 9ala2y are the giant olecular clouds of = and "O gas found?A) They appear to $e uniforly spread throughout the 9ala2y+ $oth in and a$ove and

$elow the spiral ars.

B) At the center of the 9ala2y") A$ove and $elow the plane of the spiral ars+ over the galactic poles

#) Along the spiral ars

Ans& #

'ection& 1-

5.=ow does an interstellar cloud collapse to $ecoe a star?

A) The innerost part collapses first+ then the outer part is drawn in $y the gravity ofthe inner part.

B) The collapse is tur$ulent and chaotic+ with no overall pattern.

") The outer+ less dense+ part falls in first and its weight accelerates the collapse of theinner part.

#) All parts of the cloud accelerate inward ore or less soothly and evenly.

Ans& A

'ection& 1-

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5,.The characteristics of an open cluster of stars are

A) a few hundred e$ers+ often very young and still e$edded in the gas and dustfro which they were fored.

B) hundreds of thousands of e$ers+ all very old+ surrounded $y very little

interstellar gas and dust.") a few doEen e$ers+ the renant of a glo$ular cluster of stars fro which ost

of the e$ers have escaped.

#) any thousands of e$ers of different ages.Ans& A

'ection& 1-

5/.(n which one of the following locations are clups of gas ost li%ely to $e collapsing tofor stars?

A) (n the outer part of our solar syste ") (n reflection ne$ulae

B) (n a glo$ular cluster #) (n giant olecular clouds

Ans& #'ection& 1-

5.What is a protostar?

A) A sphere of gas after collapse fro an interstellar cloud $ut $efore nuclear

reactions have $egunB) A sall interstellar cloud $efore it collapses to $ecoe a star

") A star near the end of its life $efore it e2plodes as a supernova

#) A shell of gas left $ehind fro the e2plosion of a star as a supernova

Ans& A'ection& 1-

55.At what stage in its life does a star pass through the protostar phase?A) While it is converting hydrogen into heliu in its core

B) When it is e2panding in siEe as a red giant or supergiant

") After nuclear reactions end in its core $ut $efore the red giant phase#) After condensation $ut $efore nuclear reactions $egin in its core

Ans& #

'ection& 1-

56.Where in the universe would you loo% for a protostar?

A) Near $lac% holes ") (n the epty space $etween gala2ies

B) (n dense dust and gas clouds #) (n glo$ular clusters of starsAns& B

'ection& 1-

5:.Irotostars are

A) very young o$Fects still contracting $efore $ecoing true stars.

B) old stars contracting after using up all of their availa$le hydrogen fuel.

") o$Fects with asses less than a$out >.>: solar asses that do not have enough ass

Page 12




to $ecoe true stars.

#) stars ade alost entirely out of protons.

Ans& A'ection& 1-

5<.'tar foration ta%es place inA) giant olecular clouds.

B) glo$ular clusters.

") $lue reflection ne$ulae.#) hot+ tur$ulent gas thrown out in a supernova e2plosion.

Ans& A

'ection& 1-

6>.Irotostars+ when they first for fro the interstellar ediu+ are usually

A) very $right in ultraviolet light due to nuerous flares that are hotter and $righter

than solar flares.

B) detected $y eission lines in their visi$le spectra+ eitted $y gas $eing $lown offtheir surfaces into space.

") easily detected $ecause their light ioniEes the surrounding interstellar gas+ orreflection ne$ulae.

#) hidden fro sight $y dust clouds that eit infrared radiation.

Ans& #'ection& 1-

61.Which range of electroagnetic radiation is useful for o$serving new$orn protostars

within their gas and dust ne$ulae?A) (nfrared B) isi$le ") =ighly penetrating -ray #) adio

Ans& A

'ection& 1-

6.The source of a protostarDs heat is

A) gravitational energy released as the protostar e2pands.B) nuclear reactions converting heliu to car$on and o2ygen in its core.

") gravitational energy released as the star contracts.

#) nuclear reactions converting hydrogen into heliu in its core.

Ans& "'ection& 1-

6,.The aFor source of energy in the preJain-se*uence life of the 'un wasA) nuclear fusion. ") gravitation.

B) $urning of car$on atos. #) nuclear fission.

Ans& "'ection& 1-

6/.Irotostars are

A) slowly e2panding at the surface while the core contracts.

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B) slowly contracting and heating up.

") slowly heating up and e2panding.

#) slowly contracting and cooling.Ans& B

'ection& 1-

6.What is $elieved to $e the ost iportant factor deterining whether a collapsing region

7dense core) in an interstellar cloud $ecoes a single-star or a ultiple-star syste?

A) The fraction of heavy eleents in the cloudB) The teperature

") The ass of the collapsing region

#) The aount of rotation 7spin)

Ans& #'ection& 1-

65.Accretion of atter within an interstellar cloud leads to

A) a supernova e2plosion since accretion is a nuclear process.B) e2plosion of this atter when it is attracted to+ and falls onto the surfaces of+ stars.

") the foration of olecules fro atoic gases.#) a protostar.

Ans& #

'ection& 1-

66.(n order to produce protoplanets around a new star within a condensing interstellar cloud+

a necessary condition sees to $e that the cloud ust

A) $e rotating.B) have a relatively high teperature.

") have no rotational otion at all.

#) contain a high fraction of its ass as dust.Ans& A

'ection& 1-

6:.=ow uch tie does it ta%e for a 1-solar-ass protostar to finish accreting ass fro the

interstellar cloud?

A) 1>+>>> years B) 1>>+>>> years ") 1 $illion years #) 1> illion years

Ans& B'ection& 1-,

6<.=ow large was the 'un when it first fored as a protostar?A) A$out five ties its present diaeter

B) A$out fifteen ties its present diaeter

") A$out fifty ties its present diaeter #) The sae diaeter that it has now

Ans& A

'ection& 1-,

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:>.What is the ost iportant process causing a protostar to stop accreting ass?

A) adiation and particles fro the hot protostar push infalling atter away fro the

protostar.B) Other protostars fored in the vicinity pass randoly through the infalling aterial

and eventually disperse it.

") The dense core spins up as it collapses+ and eventually the infalling atter is heldaway fro the protostar $y the centrifugal force.

#) All of the infalling atter has $een used up in the accretion.

Ans& A'ection& 1-,

:1.What is a protostar called in the stage after it has finished accreting ass?

A) A white dwarf ") A preJain-se*uence star B) A red giant 7or supergiant) #) A ain-se*uence star

Ans& "

'ection& 1-,

:.=ow long does it ta%e for a one-solar-ass star to pass through the preJain-se*uence

phase?A) 1> illion years B) 1>+>>> years ") 1> $illion years #) 1>>+>>> years

Ans& A

'ection& 1-,

:,.At what point in its evolution will a protostar stop shrin%ing and sta$iliEe into a star?

A) When nuclear processes generate enough energy and internal pressure to resist

gravitational contractionB) When gravitational contraction has heated up the gas to the point where radiation

pressure opposes gravity for the first tie

") When it has spun off enough of its atter and is spinning fast enough thatcentrifugal force opposes the gravitational contraction

#) When nuclear reactions end in its core

Ans& A'ection& 1-,

:/.What event occurs at the end of the protostar stage of a starDs life?

A) (t e2plodes+ foring a supernova renant.B) 9as is spun off fro its e*uator+ fro which planets ay for.

") Nuclear reactions $egin in its core+ converting hydrogen into heliu.

#) (t $egins a long period of contraction in which gravitational energy is convertedinto heat.

Ans& "

'ection& 1-,

:.(f a protostar were a$le to contract 7get saller) without any change to its surface

teperature+ what would happen to its luinosity?

A) (t is not possi$le to predict the change in luinosity since other factors are

Page 1!




involved.

B) (t would increase due to the copression of the gas.

") (t would decrease due to the reduced surface area of the protostar.#) (t would reain the sae since the teperature does not change.

Ans& "

'ection& 1-,

:5.What point defines the end of the preJain-se*uence phase of a starDs life and the start of

the ain-se*uence phase?A) The star $egins to e2pand and $ecoe a red giant.

B) "onvection $egins in its interior.

") The star stops accreting ass fro the interstellar cloud.

#) Nuclear reactions $egin in its core.Ans& #

'ection& 1-,

:6.At what teperature do nuclear reactions $egin in the core of a preJain-se*uence star?A) 1>> illion 8 B) 1 illion 8 ") 1> illion 8 #) 1>>+>>> 8

Ans& "'ection& 1-,

::.All $ut one of the following conditions characteriEe a preJain-se*uence star in its finalstages. Which one is the e2ception?

A) (t is fusing hydrogen into heliu in its core.

B) (t is no longer contracting.

") The gas and dust around the preJain-se*uence star have largely dissipated.#) =eliu $urning has $egun as the principal energy generating echanis in the

core.

Ans& #'ection& 1-,

:<.(n which region of the =ertEsprung-ussell diagra will a newly fored protostar firstappear when it $egins to shine at visi$le wavelengths?

A) The $otto right cornerL very low luinosity $ecause it is $oth sall and cool

B) The center of the ain se*uence since all protostars $egin their lives at this position

and ove up or down it depending upon their ass as tie passes") The right sideL relatively large luinosity $ecause of its siEe $ut cool

#) The top left cornerL at the top of the ain se*uence+ down which it will progress

with tieAns& "

'ection& 1-/

<>.Which part of the =ertEsprung-ussell diagra is occupied $y protostars?

A) To the left of the ain se*uence

B) A $and running fro upper right to lower left

") A $and running fro upper left to lower right

Page 1"




#) To the right of the ain se*uence

Ans& #

'ection& 1-/

<1.A protostar of a$out 1 solar ass is gradually contracting and $ecoing hotter. This will

cause its position in the =ertEsprung-ussell diagra to shift slowlyA) upward and toward the right. ") upward and toward the left.

B) downward and toward the left. #) downward and toward the right.

Ans& B'ection& 1-/

<.@or any star on the ain se*uence+ the sae star when it was a protostar was

A) larger and hotter. ") cooler $ut not necessarily larger.B) hotter $ut not necessarily larger. #) larger and cooler.

Ans& #

'ection& 1-/

<,.The 3evolutionary trac%4 of a star represents

A) its or$it around the center of the gala2y in which it resides.B) changes in its luinosity and teperature on a graph of these two paraeters as the

star ages.

") its path across our s%y as a conse*uence of its true otion in space.#) changes in its siEe and ass on a graph of these two paraeters as the star ages.

Ans& B

'ection& 1-/

</.The lowest ass that a protostar can have and still $ecoe a star 7i.e.+ start theronuclear

reactions in its core) is

A) slightly less than 1M1> of a solar ass.B) slightly less than 1M1>> of a solar ass.

") :M1> of a solar ass.

#) a$out 1M a solar ass.Ans& A

'ection& 1-/

<.The sallest ass that a ain-se*uence star can have is a$out >.>: solar ass. Thereason for this is that

A) theronuclear reactions $egin so suddenly in stars of less than >.>: solar ass that

the star is disrupted $y an e2plosion.B) protostars cannot for with asses less than >.>: solar ass.

") protostars of less than >.>: solar asses are not assive enough to contract.

#) the teperature in a contracting protostar of less than >.>: solar asses does notget high enough for nuclear reactions to start.

Ans& #

'ection& 1-/

Page 1#




<5.What is the lowest ass that an o$Fect can have and still $e a star?

A) >.>> solar asses 7twice KupiterDs ass)

B) >.:> solar asses") >.>: solar asses

#) >.> solar asses

Ans& "'ection& 1-/

<6.(n our solar syste+ a ne$ula is $elieved to have fored around the early 'un.Ilanetesials gradually coalesced out of this ne$ula and accreted to for the planetsa

process re*uiring a total of a$out 1>> illion years. =ow would you descri$e the 'un at

the end of this process?

A) (t was a$out half way through its protostar phase.B) (t had Fust $ecoe a preJain-se*uence star.

") (t was at the end of its e2istence as a preJain-se*uence star.

#) (t had ended its preJain-se*uence phase and had $ecoe a ain-se*uence star.

Ans& B'ection& -, and 1-/

<:.What is the relationship $etween the ass of a protostar and the tie needed for it to

reach the ain se*uence after it fors inside an interstellar cloud?

A) ore assive protostars reach the ain se*uence in a shorter tie than lessassive protostars.

B) !ess assive protostars reach the ain se*uence in a shorter tie than ore

assive protostars.

") The tie needed is independent of the ass of the protostar.#) The tie needed is least for a protostar of appro2iately / solar asses and longer

for protostars of either greater or lesser ass.

Ans& A'ection& 1-/

<<.=ow long did the 'un spend in the protostar phase of its life?A) /.5 $illion years B) />>+>>> years ") >+>>> years #) > illion years

Ans& #

'ection& 1-/

1>>.'uppose that an astronoy news ite announces the discovery of a $rown dwarf. What is

it that has $een discovered?

A) A prestellar o$Fect undergoing gravitational collapseB) A Ilutoli%e o$Fect in the 8uiper $elt+ $eyond the edge of the planetary syste

") An o$Fect too large to $e a planet $ut too sall to $e a star

#) A protostar still e$edded in the cloud of gas and dust fro which it foredAns& "

'ection& 1-/

1>1.A $rown dwarf is

Page 1$






#) The teperature $ecoes so high that the e2cess ass is pushed $ac% into space $y

radiation fro the star.

Ans& #'ection& 1-/

1>6.What appears to $e the liit to the aount of ass that can accuulate into a star $eforeenergy fro intense nuclear fusion+ eitted in the for of electroagnetic radiation+

eFects further ass away fro the star?

A) At least 1> solar assesB) Only a$out , solar asses+ hence the siilarity of all o$served stars

") 1> solar asses

#) 1>5 solar asses

Ans& A'ection& 1-/

1>:.ain-se*uence stars apparently do not have asses larger than a few hundred solar

asses. The reason that stars of larger ass do not e2ist is thatA) their teperature $ecoes so high that they are disrupted $y the pressure of

radiation inside the.B) the theronuclear reactions in such stars proceed so rapidly that the star e2plodes.

") such stars contract directly to $ecoe planetli%e o$Fects.

#) interstellar clouds of greater ass $rea% up to $ecoe $inary or ultiple-starsystes+ not single stars.

Ans& A

'ection& 1-/

1><.The Orion Ne$ula is

A) a spiral gala2y in the constellation Orion.

B) a red supergiant star.") a large interstellar gas and dust cloud containing young stars.

#) a supernova renant+ the aterial thrown out $y an e2ploding star.

Ans& "'ection& 1-

11>.(nfrared stars within the Orion Ne$ula are e2aples of which stage of stellar evolution?

A) ed-giant ") 'upernova renantsB) Irotostar and young star #) Ilanetary ne$ula

Ans& B

'ection& 1-

111.(nfrared stars within the Orion ne$ula are e2aples of which stage of stellar evolution?

A) Irotostar and young star ") Ilanetary ne$ulaB) ed-giant #) 'upernova renants

Ans& A

'ection& 1-

Page 2&




11.What is a T Tauri star?

A) A young 9+ 8+ or star that is eFecting gas

B) A giant or supergiant star that varies regularly in $rightness") A giant or supergiant star that varies randoly in $rightness

#) A assing O or B star that ioniEes hydrogen in interstellar space

Ans& A'ection& 1-

11,.What nae is given to a young+ cool star 7spectral class 9+ 8+ or ) that is eFecting gasinto the interstellar ediu?

A) A "epheid varia$le B) A flare star ") A !yrae star #) A T Tauri star

Ans& #

'ection& 1-

11/.A T Tauri star is at what stage of its stellar evolution?

A) Kust $efore red-giant phase+ when varia$ility $egins

B) Well esta$lished on the ain se*uence") At the end of its life+ decaying away and cooling

#) Irotostar+ $efore ain-se*uence phaseAns& #

'ection& 1-

11.T Tauri stars are at what stage of stellar evolution?

A) ain-se*uence+ or 3iddle age4

B) =oriEontal-$ranch phase

") 0arly phases& after the foration of a protostar $ut $efore the ain se*uence#) IostJain-se*uence $efore heliu shell flash

Ans& "

'ection& 1-

115.A T Tauri star is

A) a protostar that is eFecting ass near the end of its preJain-se*uence lifetie.B) a young+ assive O or B star.

") a young protostar e$edded in a cocoon of dust clouds+ visi$le only $y infrared

radiation.

#) a high-ass yellow giant star that pulsates regularly in siEe and $rightness.Ans& A

'ection& 1-

116.Which of the following is NOT a characteristic of T Tauri stars?

A) ariations in $rightness ") Nuclear reactions in the core

B) 0Fection of ass into space #) 0ission lines in the spectruAns& "

'ection& 1-

11:.Which of the following stateents descri$es a %nown characteristic of a T Tauri star?

Page 21




A) 0Fection of ass into space

B) 9reat age+ near the end of its life as a star

") =igh ass+ greater than a$out , solar asses#) Nuclear reactions in the core

Ans& A

'ection& 1-

11<.On a =ertEsprung-ussell diagra descri$ing the stars in a young cluster+ in which

position would you e2pect to find the T Tauri stars?A) Well a$ove the ain se*uence and to the left of the diagra

B) Kust a$ove and slightly to the right of the ain se*uence

") Well $elow the ain se*uence

#) (n the upper right of the diagra+ well a$ove the ain se*uenceAns& B

'ection& 1-

1>.Of the following facts referring to stars in a cluster+ which is NOT particularly useful forinterpreting the evolution of these stars?

A) The stars are all at the sae distance fro the 0arth+ and so we easure trueintrinsic $rightnesses of the stars.

B) The stars all fored at a$out the sae tie.

") The stars fored fro the sae i2 of cheical eleents $ut with a i2 oforiginal asses.

#) The aFority of the aterial in these stars is hydrogen.

Ans& #

'ection& 1-

11.(f we plotted the stars in a GOCN9 star cluster on a =ertEsprung-ussell diagra+ we

would e2pect to seeA) all stars on the ain se*uence.

B) the ore assive stars a$ove the ain se*uence and the less assive stars on the

ain se*uence.") soe stars on the ain se*uence and others a$ove the ain se*uence+ in rando

fashion depending on when each individual star condensed fro the interstellar

cloud.

#) the ore assive stars on the ain se*uence and the less assive stars a$ove theain se*uence.

Ans& #

'ection& 1-

1.An astronoer plots the =- diagra of a star cluster and finds that it contains hot B-

type stars on the ain se*uence and cooler 9- and 8-type stars noticea$ly a$ove theain se*uence. This cluster is

A) of indeterinate age since one cannot estiate the age of the cluster fro the

inforation given.

B) ipossi$le $ecause one cannot have cool stars a$ove the ain se*uence when hot

Page 22




stars are on the ain se*uence.

") old $ecause the 9 and 8 stars are already evolving off 7away fro) the ain

se*uence.#) very young $ecause the 9 and 8 stars are still evolving toward the ain se*uence.

Ans& #

'ection& 1-

1,.When plotted on an =- diagra+ a particular star cluster has its ore assive stars on

the ain se*uence and its less assive stars a$ove the ain se*uence. "an we find theage of this cluster? 7i.e.+ =ow long is it since these stars condensed fro the interstellar

ediu?)

A) Ges+ $y finding the ost assive star that is on the ain se*uence. The age of the

cluster e*uals the tie that this star spent as a protostar.B) No

") Ges+ $y finding the least assive protostar. The age of the cluster e*uals the tie

that this star ta%es to reach the ain se*uence.

#) Ges+ $y finding the least assive star that is on the ain se*uence. The age of thecluster e*uals the tie that this star spent as a protostar.

Ans& #'ection& 1-

1/.(n a group of stars with a range of asses+ stars with different assA) will leave the ain se*uence of the =ertEsprung-ussell diagra at different ties

after their $irth.

B) have a$out the sae age+ assive stars $urning their fuel ore rapidly than low-

ass stars to accoplish this.") all go through the supernova phase of evolution after varying ties $eyond their

$irths.

#) all pass+ at soe stage in their evolution+ through one particular point on the=ertEsprung-ussell diagra+ occupied at present $y the 'un.

Ans& A

'ection& 1-

1.The total lifespan of the 'un is $elieved to $e

A) a few illion years. B) half a $illion years. ") 1> $illion years. #) infinite.

Ans& "'ection& 1-5

15.(n the =ertEsprung-ussell diagra+ how does the position of a typical star change whileit is at the ain-se*uence phase of its evolution?

A) 'tars ove fro upper right to lower left while they are on the ain se*uence.

B) 'tars ove fro upper left to lower right while they are on the ain se*uence.") assive stars 7/ solar asses) ove toward the upper left as their luinosity

increases+ while lower-ass stars ove toward the lower right as their teperature

decreases.

#) A starDs position on the ain se*uence is deterined only $y its ass and not its

Page 23




age+ and so stars do not ove along the ain se*uence during evolution.

Ans& #

'ection& 1-5

16.The definition of a ain-se*uence star is one

A) with a surface teperature e*ual to that of the 'un.B) in which nuclear fusion reactions generate sufficient energy to oppose further

condensation of the star.

") whose age after $irth is a$out 1 illion years.#) with a luinosity precisely e*ual to that of the 'un.

Ans& B

'ection& 1-5

1:.At what stage of its evolutionary life is the 'un?

A) ain se*uence+ or 3iddle age4

B) IreJain se*uence+ varia$le star

") Kust $efore supernova stage 7perhaps years)+ late evolutionary stage#) IostJain se*uence+ red-giant 7cool) phase

Ans& A'ection& 1-5

1<.What aFor physical process is ta%ing place inside stars that are on the ain se*uence inthe =ertEsprung-ussell diagra?

A) =ydrogen is $eing converted to heliu in their cores.

B) =ydrogen is $eing converted to heliu in a shell around the heliu-rich core.

") =eliu is $eing converted to car$on in their cores.#) The gas is contracting gravitationally without nuclear reactions ta%ing place.

Ans& A

'ection& 1-5

1,>.Theronuclear reactions convert hydrogen into heliu in the core of a star during which

phase of a starDs life?A) The ain-se*uence phase

B) The protostar phase

") The horiEontal-$ranch phase

#) As the star oves up the red-giant $ranch for the first tieAns& A

'ection& 1-5

1,1.All stars on the ain se*uence

A) generate energy $y hydrogen fusion in their centers.

B) have appro2iately the sae age+ to within a few illion years.") are changing slowly in siEe+ $y gravitational contraction.

#) are at a late stage of evolution+ after the red-giant stage.

Ans& A

'ection& 1-5

Page 2




1,.What is happening in a star that is on the ain se*uence on the =ertEsprung-ussell

diagra?A) The star is generating energy $y heliu fusion+ having stopped hydrogen

3$urning.4

B) The star is slowly shrin%ing as it slides down the ain se*uence fro top left to $otto right across the =- diagra.

") 'tars that have reached the ain se*uence have ceased nuclear 3$urning4 and are

siply cooling down $y eitting radiation.#) The star is generating internal energy $y hydrogen fusion.

Ans& #

'ection& 1-5

1,,.The 3Eero-age ain se*uence4 descri$es the se*uence of stars in the =ertEsprung-ussell

diagra

A) that contain no processed eleents 7eleents heavier than hydrogen or heliu).

B) that are Fust $eginning to convert heliu into car$on in their cores.") that have Fust collapsed fro the interstellar ediu.

#) that have Fust reached the ain se*uence.Ans& #

'ection& 1-5

1,/.Why is it that the aFority of stars in the s%y are in the ain-se*uence phase of their

lives?

A) Because ost stars die at the end of the ain-se*uence phase

B) Because this is the longest-lasting phase in each starDs life") Because this is the only phase that is coon to all stars

#) Because ost stars in the s%y were created at a$out the sae tie+ so these are all

in the sae phase of their livesAns& B

'ection& 1-5

1,.=ow is the length of a starDs lifetie related to the ass of the star?

A) !ower-ass stars run through their lives faster and have shorter lifeties.

B) The lifeties of stars are too long to easure+ so it is not %nown how 7or if) their

lifeties depend on ass.") A starDs lifetie does not depend on its ass.

#) =igher-ass stars run through their lives faster and have shorter lifeties.

Ans& #'ection& 1-5

1,5.The stars that last longest areA) those with the largest luinosity and highest teerature since they will ta%e the

longest to cool down to invisi$ility.

B) those with the largest ass+ that is+ the largest aount of fuel.

") those with the sallest ass.

Page 2!




#) stars of interediate assL sall-ass stars have little fuel and $urn out *uic%ly+

while very assive stars $urn their fuel very rapidly.

Ans& "'ection& 1-5

1,6.(n ters of the ass and lifetie of a star+ which of the following stateents is true?A) The ass of a star has no $earing on the length of a starDs life or the speed of its

evolution.

B) 'tars of a$out 1 solar ass have the shortest livesL less assive stars evolve slowlyand live a longer tie+ while ore assive stars have long lives $ecause of the

large aount of fuel they contain.

") The less assive the star+ the shorter its life+ $ecause it has less hydrogen 3fuel4 to

$urn.#) The ore assive the star+ the faster it will evolve through its life.

Ans& #

'ection& 1-5

1,:.What is the ost iportant property of a star that governs its evolution and lifetie?

A) The ass of the star B) (ts surface teperature

") The a$undance of heavy eleents in the star

#) The starDs speed of rotationAns& A

'ection& 1-5

1,<.=ow long will the 'un have spent as a ain-se*uence star when it finally $egins toevolve toward the red-giant phase?

A) 1 $illion years B) 1 illion years ") 1>11 years #) 1>1> years

Ans& #'ection& 1-5

1/>.The total tie that the 'un will spend as a ain-se*uence star isA) at least >> $illion years 7 1>11) years.

B) a$out 1 illion years.

") a$out /. illion years.

#) a$out 1> $illion years 71>1> years).Ans& #

'ection& 1-5

1/1.Appro2iately what fraction of its ain-se*uence lifetie has the 'un copleted at the

present tie 7see "oins and 8aufann+ Discovering the Universe+ 6th 0d.+ Ta$le 1-1)?

A) A$out 1M/ B) !ess than 1> ") A$out 1M #) A$out ,M/Ans& "

'ection& 1-5

1/.Over which of the following stages of stellar evolution does the radius of a star reain

Page 2"




appro2iately constant?

A) ain-se*uence phase ") ed-giant phase

B) Asyptotic giant-$ranch phase #) Birth and initial forationAns& A

'ection& 1-5

1/,.Which of the following stateents a$out the rate of stellar evolution is true?

A) The ore assive the original star+ the faster the evolution.

B) The cheical a%e-up of the original ne$ula is the aFor factor in deciding the rateof evolution+ whatever the ass of the star.

") 'tar ass has no $earing on stellar evolution since all stars evolve at the sae rate+

controlled $y nuclear fusion.

#) The ore assive the original star+ the slower the evolution+ since there is oreaterial for theronuclear $urning.

Ans& A

'ection& 1-5

1//.(f a star is on or close to the ain-se*uence region of the =ertEsprung-ussell diagra+

what particular feature of stellar $ehavior can $e inferred $y this o$servation?A) The star is generating internal energy $y hydrogen fusion.

B) The star is generating energy $y heliu fusion+ having stopped hydrogen

3$urning.4") The star is slowly shrin%ing and there$y releasing gravitational potential energy as

it slides down the ain se*uence fro top left to $otto right across the =-

diagra.

#) 'tars that have reached the ain se*uence have ceased nuclear 3$urning4 and aresiply cooling down $y eitting radiation.

Ans& A

'ection& 1-5

1/.The ain-se*uence lifetie of a star with half the ass of the 'un

A) could $e longer or shorter than that of the 'unL ore inforation is re*uired toanswer this *uestion.

B) is longer than that of the 'un.

") is the sae as that of the 'un+ $ecause ass does not affect the lifetie of a star.

#) is shorter than that of the 'un.Ans& B

'ection& 1-5

1/5.=ow long does a star of three ties the 'unDs ass live copared to the lifetie of the

'un? 7'ee Ta$le 1-1+ "oins and 8aufann+ Discovering the Universe+ 6th 0d.)

A) (t lives a$out 1M, as long as the 'un.B) (t lives a$out 1M> as long as the 'un.

") (t lives a$out , ties as long as the 'un.

#) (t lives a$out 1M>> as long as the 'un.

Ans& B

Page 2#




'ection& 1-5

1/6.The present estiate of the age of the universe is a$out 1 $illion years. =ow long will ahalf-solar-ass star spend on the ain se*uence+ copared to the present age of the

universe? 7'ee Ta$le 1-1+ "oins and 8aufann+ Discovering the Universe+ 6th 0d.)

A) A$out , ties the age of the universeB) ore than 1> ties the age of the universe

") !ess than 1M1> of the age of the universe

#) A$out 1M of the age of the universeAns& B

'ection& 1-5

1/:.The star Eeta Iegasi 7in the constellation Iegasus+ the @lying =orse) has a spectral-luinosity class of B: + which gives it a surface teperature of a$out 11+>>> 8.

According to Ta$le 1-1 of "oins and 8aufann+ Discovering the Universe+ 6th 0d.+

the e2pected ain-se*uence lifetie of Eeta Iegasi is

A) uch greater than >> illion years.B) a$out >> illion years.

") not defined in any way at all $y this inforation.#) a$out >>+>>> years.

Ans& B

'ection& 1-5

1/<.The spiral gala2y in which we live is roughly 1 $illion years old. @or the stars that

fored when the 9ala2y was very young 7say+ during the first $illion years)+ which of the

following stateents is true? 7'ee Ta$le 1-1+ "oins and 8aufann+ Discovering theUniverse+ 6th 0d.)

A) No stars are still on the ain se*uencein this tie all stars will have finished

their lives.B) All stars of less than ,M/ of the ass of the 'un are still on the ain se*uence.

") All stars of ore than 1 ties the ass of the 'un are still on the ain se*uence.

#) All stars of , ties the ass of the 'un are still on the ain se*uence.Ans& B

'ection& 1-5

1>.(f you were a$le to return to the 0arth 1 illion years into the future+ which of thefollowing views of the s%y would $e ost li%ely?

A) A few red stars would $e issing since they would have evolved+ $ut otherwise

stars would $e the sae+ and $e in the sae positions+ as they are today.B) Near$y stars would have oved in position+ and no $lue stars would $e visi$le.

") Near$y stars would have oved in position and soe stars that are presently $lue

would have changed color+ $ut otherwise the s%y would $e very uch as it is now+since 1 illion years is a very short tie in astronoical ters.

#) All the present stars+ $oth $lue and red+ would $e visi$le+ $ut near$y stars would

have oved in position.

Ans& "

Page 2$






'ection& 1-6

15.Of all the low-ass red dwarfs 7>.>: . P P >./

.) that have fored since the 9ala2y

cae into $eing 1 $illion years ago+ how any of the are presently on the ain

se*uence?

A) None of the ") ost of the+ ore than :>B) A few+ less than > #) All of theAns& #

'ection& 1-6

16.A low-ass red dwarf 7>.>: .

P P >./ .

) e2periences which of the following as the

last fusion reaction in its core?A) =ydrogen fusion B) =eliu fusion ") "ar$on fusion #) 'ilicon fusion

Ans& A

'ection& 1-6

1:.A low-ass red dwarf 7>.>: . P P >./ .) will eventually $ecoeA) a red giant. B) a $rown dwarf. ") a white dwarf. #) None of the a$ove

Ans& #'ection& 1-6

1<.(f you were to loo% at 1 %ilogra of aterial ta%en fro the surface of the 'un and 1%ilogra ta%en fro the center+ which of the following stateents would $e true of these

two %ilogras?

A) They $oth have the sae aount of hydrogen and are in fact ostly hydrogen.B) The %ilogra fro the surface contains ore hydrogen than the one fro the

center.

") Neither of the contain any hydrogen.#) The %ilogra fro the surface contains less hydrogen than the one fro the center.Ans& B

'ection& 1-:

15>.Why does the core of the 'un contain ore heliu and less hydrogen than the surface of

the 'un?

A) The hydrogen has $een lifted out of the core $y the 'unDs agnetic field.B) =eliu is heavier than hydrogen and has sun% toward the center in a process of

cheical differentiation.

") =eliu condenses ore easily+ so when the 'un was foring the core $ecae

heliu-richL vast *uantities of hydrogen were added only after the core $ecaeassive enough.

#) Theronuclear reactions have converted uch of the original hydrogen in the core

into heliu.Ans& #

'ection& 1-:

151.When a star leaves the ain se*uence and e2pands toward the red giant region+ what is

Page 3&




happening inside the star?

A) =eliu $urning is ta%ing place in a spherical shell Fust outside the coreL the core

itself is alost pure car$on and o2ygen.B) =ydrogen $urning is ta%ing place in a spherical shell Fust outside the coreL the core

itself is alost pure heliu.

") =ydrogen $urning is ta%ing place in a spherical shell Fust outside the coreL the corehas not yet started theronuclear reactions+ and is still ostly hydrogen.

#) =eliu is $eing converted into car$on and o2ygen in the core.

Ans& B'ection& 1-:

15.(n ters of nuclear reactions+ what is the ne2t stage of a starDs life after the end of

hydrogen $urning in the core?A) =ydrogen $urning in a thin shell around the core

B) =eliu $urning in the core

") "ar$on $urning

#) #eath 7it $ecoes either a supernova or a white dwarf)Ans& A

'ection& 1-:

15,.The ne2t stage in a starDs life after the ain-se*uence phase is

A) the red-giant phase.B) the horiEontal-$ranch phase.

") a protostar.

#) death 7i.e.+ either a supernova or a white dwarf).

Ans& A'ection& 1-:

15/.The energy eitted $y a star increases as the fourth power of its surface teperature anda red giant star has a lower teperature than the 'un. Why then is the luinosity of a red

giant a$out a thousand ties larger than that of the 'un?

A) Because it is $igger and therefore has a uch larger surface areaB) Because the energy transfer fro red giantDs interior is uch ore efficient than it

is in the 'un

") Because ore of its total output of energy is in the visi$le range than that of the

'un and hence the red giant appears $righter #) Because the red giantDs nuclear furnace is producing uch ore energy than that of

the 'un

Ans& A'ection& 1-:

15.Which of the following are NOT very young stars or prestellar o$Fects?A) ed giants

B) (nfrared-eitting stars in gas and dust clouds

") Irotostars

#) T Tauri stars

Page 31




Ans& A

'ection& 1-:

155."opared to the coposition of the early 'un+ the coposition of the gas at the core of a

star that has Fust $ecoe a red giant is

A) very different since theronuclear fusion has transfored all the hydrogen andheliu into heavier eleents.

B) very different+ with lots of hydrogen $ut alost no heliu left after theronuclear

fusion.") very different since theronuclear fusion has transfored all the hydrogen into

heliu.

#) the sae+ with a high fraction of hydrogen copared to heliu since these stars

were produced with the sae initial aterial.Ans& "

'ection& 1-:

156.What a%es a red giant star so large?A) The heliu-rich core has e2panded+ pushing the outer layers of the star outward.

B) The hydrogen-$urning shell is heating the envelope and a%ing it e2pand.") ed giants are rapid rotators+ and centrifugal force pushes the surface of the star

outward.

#) The star has any ties ore ass than the 'un.Ans& B

'ection& 1-:

15:.What rates of ass loss are typical fro red giant stars?A) 1> J1/ of a solar ass per year

B) 1> J, of a solar ass per year

") ed giant stars do not suffer ass loss#) 1> J6 of a solar ass per year

Ans& #

'ection& 1-:

15<.The aFority of the eleents heavier than hydrogen and heliu in the universe are

$elieved to have originated

A) in the original Big Bang. ") in giant olecular clouds.B) in reflection ne$ulae. #) in the central cores of stars.

Ans& #

'ection& 1-:

16>.Why are higher gas teperatures in the core of a star re*uired in order to produce nuclear

fusion of heliu copared to that re*uired for hydrogen?A) Because the heliu nuclei need to $e oving faster in order to avoid the ore

nuerous and faster hydrogen nuclei+ with which they can co$ine with no energy

generation.

B) Because higher speeds are needed $etween two heliu atos in order to overcoe

Page 32




the shielding effect of the two electrons around the nucleus copared to the one

electron per nucleus of hydrogen.

") Because higher atoic speeds are re*uired in order to strip off two electrons perheliu ato rather than one electron per ato for hydrogen $efore fusion can ta%e

place.

#) Because higher collision speeds are needed to overcoe the e2tra electrostaticrepulsion $etween dou$ly charged heliu nuclei.

Ans& #

'ection& 1-:

161.=ow large will the 'un $e as a red giant?

A) A$out 1 AC radius 7out to the 0arthDs or$it)

B) A$out 1M1> AC radius 71M/ of ercuryDs or$it)") A$out 1. AC radius 7out to arsDs or$it)

#) A$out 1M AC radius 7$eyond ercuryDs or$it)

Ans& A

'ection& 1-:

16.When core heliu $urning $egins in the 'un+ the 'un will have a siEe 7diaeter) roughlye*ual to

A) half the siEe of the 0arthDs or$it. ") half its present siEe.

B) the siEe of the 0arth. #) twice its present siEe.Ans& A

'ection& 1-:

16,.Which of the following characteriEes the early stages of a red giant?A) A large+ red star that is $urning hydrogen into heliu in its core

B) A protostar in the 3upper right4 part of the =ertEsprung-ussell diagra

") A large-eission ne$ula#) A star that is $urning hydrogen into heliu in a shell around the core

Ans& #

'ection& 1-<

16/.What happens to the heliu-rich core of a star after the core runs out of hydrogen?

A) (t cools down and contracts. ") (t heats up and e2pands.

B) (t e2pands and cools down. #) (t contracts and heats up.Ans& #

'ection& 1-<

16.After the heliu flash in a low-ass star

A) all nuclear reactions cease.

B) heliu $urning ceases in the core+ $ut hydrogen $urning continues in the layersaround the core.

") heliu $urning $egins in the core+ and hydrogen $urning ceases in the layers

around the core.

#) heliu $urning $egins in the core+ and hydrogen $urning continues in the layers

Page 33




around the core.

Ans& #

'ection& 1-<

165.Nuclear fusion reactions that convert heliu into car$on and o2ygen in the central core of

a star occur during which phase of a starDs life?A) (n the red-giant stage+ $efore heliu flash

B) #uring and iediately after the 7first) red-giant or supergiant stage

") #uring the protostar stage#) After the ain-se*uence phase+ $efore the star $ecoes a red giant

Ans& B

'ection& 1-<

166.=ow hot does the core of a star have to $e for heliu $urning to $egin?

A) 1>> illion 8 B) 1 $illion 8 ") 1 illion 8 #) 1> illion 8

Ans& A

'ection& 1-<

16:.The teperature at which theronuclear reactions $egin to convert heliu into car$on7heliu $urning) is

A) 1 illion 8. B) 1>> illion 8. ") 1 $illion 8. #) 1 illion 8.

Ans& B'ection& 1-<

16<.What is the doinant nuclear reaction during heliu $urning in the core of a star?

A) 1= Q /=e co$ining to for " ") =e fusing to for "B) /=e fusing to for " #) ,=e fusing to for "

Ans& #

'ection& 1-<

1:>.#uring heliu $urning in a starDs later life+ the cheical eleent produced $y the

co$ination of heliu nuclei isA) the light isotope of heliu+ ,=e. ") $erylliu+ :Be.

B) heavy hydrogen+ =. #) car$on+ 1".

Ans& #

'ection& 1-<

1:1.#uring heliu $urning+ soe /=e co$ines with 15O+ uch li%e the way it co$ines with1" to for 15O. What is produced $y the 15O Q /=e reaction? 7The periodic ta$le shownin "hapter / of "oins and 8aufann+ Discovering the Universe+ 6th 0d.+ ay $e

useful.)

A) 1:O 7heavy isotope of o2ygen) ") Na 7light isotope of sodiu)B) > Ne 7regular isotope of neon) #) >@ 7heavy isotope of fluorine)

Ans& B

'ection& 1-<

Page 3




1:.What are the products of heliu $urning in a star?

A) agnesiu and silicon ") "ar$on and o2ygen

B) Nitrogen and o2ygen #) =ydrogen and lithiuAns& "

'ection& 1-<

1:,.=ow long does core heliu $urning last in a star copared to core hydrogen $urning?

A) A$out 1M of the tie spent $urning hydrogen

B) A$out 1M1> of the tie spent $urning hydrogen") A$out 1M1>> of the tie spent $urning hydrogen

#) A$out , ties as long as the tie spent $urning hydrogen

Ans& B

'ection& 1-<

1:/.What is the Iauli e2clusion principle?

A) Ihotons of less than a certain wavelength cannot eFect electrons fro a etal.

B) Two identical particles cannot occupy the sae place at the sae tie.") Two different atos cannot have the sae energy levels.

#) Two identical photons cannot $e a$sor$ed $y the sae ato.Ans& B

'ection& 1-<

1:.The Iauli e2clusion principle states that two identical electrons 7or other particles) cannot

have

A) the sae electrical charge at the sae tie.

B) the sae speed at the sae tie.") the sae position at the sae tie.

#) the sae speed and direction at the sae tie.

Ans& "'ection& 1-<

1:5.When is electron degeneracy pressure iportant in a star?A) Kust $efore the start of heliu $urning in the core

B) #uring core hydrogen $urning

") (n a "epheid varia$le that is $urning heliu in its core

#) (n a protostar evolving toward the ain se*uenceAns& A

'ection& 1-<

1:6.The Iauli e2clusion principle

A) prevents high-ass stars fro foring in low-ass interstellar clouds.

B) sets a liit to the crowding together of electrons into any given sall volue ofspace.

") liits the nu$er of atos that can $ecoe ioniEed in a star.

#) prevents two stars of the sae spectral class fro occupying the sae $inary star

syste.

Page 3!




Ans& B

'ection& 1-<

1::.What is the 3safety valve4 that prevents noral 7nondegenerate) stars fro self-

destructing?

A) (f the pressure rises+ the volue occupied $y the atter will decrease+ reducing thenuclear reaction rate.

B) (f a part of a star where theronuclear reactions are occurring is suddenly heated+ it

will e2pand and cool.") (f theronuclear reactions proceed too *uic%ly+ the star will run out of fuel $efore

anything drastic happens.

#) (f the teperature rises+ the theronuclear reaction rate will increase to atch it.

Ans& B'ection& 1-<

1:<.What is the 3safety valve4 that operates in noral 7nondegenerate) stars?

A) (f theronuclear reactions proceed too *uic%ly+ the star will run out of fuel $eforeanything drastic happens.

B) (f the stellar gas is suddenly heated+ it will e2pand and cool.") (f the star gets too $ig+ it will collapse into a $lac% hole.

#) (f the pressure gets too high+ electrons will co$ine with protons to relieve the

pressure.Ans& B

'ection& 1-<

1<>.A degenerate-electron gas+ such as occurs in the core of a red giant star+ lac%s the 3safetyvalve4 of a noral gas. This is $ecause

A) a rise in pressure releases ore electrons+ thus increasing the pressure further.

B) a rise in pressure reduces the nu$er of electrons+ causing the core to collapse.") a rise in teperature does not change the pressure+ so the gas does not e2pand and

cool.

#) a rise in teperature lowers the pressure+ causing the star to contract.Ans& "

'ection& 1-<

1<1.Cnder what conditions does electron degeneracy occur?A) When electrons $ecoe crowded too closely together

B) When theronuclear reactions release ore electrons than protons

") When electrons and positrons annihilate+ releasing energy#) When ultraviolet light fro hot+ young O and B stars ioniEes the interstellar

ediu

Ans& A'ection& 1-<

1<.#egeneracy occurs when

A) electrons inside a star resist $eing pushed closer together than a certain liit.

Page 3"




B) solar wind particles $ecoe trapped in the 0arthDs agnetic field.

") agnetic fields inhi$it the otion of charged particles in sunspots.

#) theronuclear reactions halt the contraction of a protostar.Ans& A

'ection& 1-<

1<,.(f electrons are collectively copressed into a very sall volue 7e.g.+ within the core of

a dying white dwarf star) where *uantu echanical considerations $ecoe iportant in

preventing one electron fro occupying space near to a second electron 7Iauli e2clusion principle)+ what is the result?

A) The electrons generate a very large pressure to oppose further copression.

B) The electrons fall into or$it around one another in utual pairs that reduce the

restricted *uantu space+ allowing further shrin%age of the star.") Nuclear fusion occurs $etween electrons+ producing energy and heating the starDs

core.

#) =alf of the electrons are transfored into antiatter 7positrons)+ which then

annihilates electrons+ producing a $urst of energy and the e2plosion of the star.Ans& A

'ection& 1-<

1</.0lectron degeneracy+ which is a result of the Iauli e2clusion principle+ is iportant

A) in a "epheid varia$le that is $urning heliu in its core.B) in the core of a star during core hydrogen $urning.

") in a protostar evolving toward the ain se*uence.

#) in the core of a star Fust $efore the start of core heliu $urning.

Ans& #'ection& 1-<

1<.The heliu flash results fro theA) sudden release of energy in strong agnetic fields near a sunspot.

B) electron degeneracy or *uantu crowding in the core of a low-ass red giant star.

") sudden onset of nuclear reactions at the end of the protostar.#) high teperature in the heliu core of a $lue 7spectral class O or B) supergiant star.

Ans& B

'ection& 1-<

1<5.Which coponent in the core of a star undergoing heliu fusion leads to the $ehavior

%nown as the 3heliu flash4?

A) Neutrinos+ since it is this coponent that+ in interacting with heliu nuclei+ triggersthe heliu flash

B) =eliu+ since its density has to $e a$ove a certain liit in order to trigger this

e2plosive event") 0lectrons+ since they control the pressure and this does not depend upon

teperature. Cnder these conditions+ $uild-up of heat can occur without leading to

the noral gas e2pansion and the resulting theral e*uili$riu.

#) enant hydrogen+ since loss of this coponent will allow uncontrolled heliu

Page 3#




$urning rather than a unifor rate of energy production

Ans& "

'ection& 1-<

1<6.The heliu flash is another nae for

A) a sudden release of energy at the end of heliu $urning due to core contraction.B) a sudden onset of heliu fusion reactions in red giant and supergiant stars of any

ass.

") a sudden onset of heliu fusion reactions in the core of a low-ass red giant star.#) the sudden appearance of heliu during a supernova e2plosion 7e2plosion of a star

at the end of its life).

Ans& "

'ection& 1-<

1<:.Which stars undergo a heliu flash in their cores?

A) All stars of less than solar asses ") All stars of ore than solar asses

B) All stars that contain heliu #) All stars that have $ecoe red giantsAns& A

'ection& 1-<

1<<.The 3heliu flash4 occurs in a -solar-ass star when

A) the core heats up fro heliu fusion and the gas does not e2pand to cool down andsta$iliEe the teperature $ecause the gas properties are controlled $y degenerate

electrons.

B) convection within the star carries heliu to the surface+ where it shows its own

characteristic spectru for the first tie.") hydrogen fusion ceases a$ruptly+ leaving only the fusion of heliu to generate

energy.

#) the core teperature $ecoes sufficiently high for heliu fusion for the first tie.Ans& A

'ection& 1-<

>>.What process is involved in the heliu flash?

A) An increase in teperature causes an increase in the nuclear reaction rate $ut has

no effect on pressure.

B) An increase in the pressure causes a decrease in the teperature and the nuclearreaction rate.

") An increase in teperature causes an increase in the pressure with no increase in

the nuclear reaction rate.#) An increase in the nuclear reaction rate causes an increase in the teperature and

the pressure.

Ans& A'ection& 1-<

>1.What happens to a star after the start of heliu nuclear reactions in its core copared to

what it was li%e $efore these reactions $egan?

Page 3$




A) The star is larger and hotter. ") The star is saller and hotter.

B) The star is larger and cooler. #) The star is saller and cooler.

Ans& "'ection& 1-<

>.After hydrogen $urning ends in a starDs core+ its position on the =ertEsprung-usselldiagra oves in a direction toward the

A) lower right. B) upper left. ") lower left. #) upper right.

Ans& #'ection& 1-1>

>,.After it leaves the ain se*uence+ a star with a ass greater than 1 solar ass oves

generally to the right on the = diagra. This happens $ecauseA) the starDs surface teperature is increasing while its radius is decreasing.

B) the starDs surface teperature is decreasing while its radius is increasing.

") the starDs core is e2panding while its outer layers are contracting.

#) the starDs core is e2panding+ causing its outer layers to e2pand as well.Ans& B

'ection& 1-1>

>/.On the =ertEsprung-ussell diagra+ in which direction does the position occupied $y a

star ove after heliu $urning $egins in the starDs core?A) Toward the upper right ") Toward the lower right

B) Toward the lower left #) Toward the upper left

Ans& B

'ection& 1-1>

>.(f the universe is only 1 $illion years old+ which of the following groups of stars have

never oved $eyond the ain se*uence?A) 'tars with asses less than >.>: solar asses

B) 'tars with asses less than >.6 solar asses

") 'tars with asses greater than 1>> solar asses#) 'tars with asses greater than 1> solar asses

Ans& B

'ection& 1-1>

>5.The stars that fored first after the initial Big Bang were

A) virtually all Iopulation ( stars.

B) virtually all Iopulation (( stars.") a$out the sae i2ture of Iopulations ( and (( that we now o$serve.

#) of an entirely different type of star that has since evolved into Iopulation ( and

Iopulation ((.Ans& B

'ection& 1-11

>6.The study of stars in clusters has especially helped astronoers to understand

Page 3%




A) stellar evolution+ the developent of stars with tie.

B) the echanis of ass loss in stars.

") the reason for differences in surface teperatures of stars.#) the action of nuclear fusion in stars.

Ans& A

'ection& 1-11

>:.The ain general features that a%e clusters of stars useful to astronoers are that

A) the stars all have the sae apparent agnitude+ the sae surface teperatures+ andthe sae siEes.

B) the stars are all at the sae distance fro the 0arth+ have the sae surface

teperature+ and Foined the cluster at various ties.

") the stars all have the sae intrinsic $rightness $ut differ only in siEe and surfaceteperature.

#) the stars are at the sae distance fro the 0arth+ were fored at appro2iately the

sae tie+ and were ade fro the sae cheical i2.

Ans& #'ection& 1-11

><.=ow any stars are there in a large glo$ular cluster?

A) A$out 1 illion B) A$out 1>>> ") Cp to 1>> $illion #) Only a few doEen

Ans& A'ection& 1-11

1>.The characteristic of a glo$ular cluster of stars is

A) hundreds of thousands of e$ers+ all very old and generally etal-poor.B) a few doEen e$ers+ the renant of a glo$ular cluster of stars fro which ost

of the e$ers have escaped.

") any thousands of e$ers of different ages.#) a few hundred e$ers+ often very young and still e$edded in the gas and dust

fro which they were fored.

Ans& A'ection& 1-11

11.What would you e2pect to find in the population of stars in a glo$ular cluster?

A) ainly white dwarf stars and the planetary ne$ular stages of dying stars+ $ut nofaint red stars+ red giants+ or $right $lue stars

B) ostly $lue giants and supergiants+ with a few red giant stars+ white dwarfs+ and

di red stars") any red giants+ white dwarfs+ and di red stars+ $ut no dust and gas

#) 'tars along the entire ain se*uence fro $right $lue to di red+ with no $right red

giant stars $ut significant aounts of dust and gasAns& "

'ection& 1-11

1.Why does the =ertEsprung-ussell diagra of a glo$ular cluster NOT contain any stars

Page &




with high luinosity and high teperature on the ain se*uence?

A) These high-ass stars evolved away fro the ain se*uence long ago.

B) 'tars that will occupy this position on the ain se*uence have not yet evolved therefro the protostar stage.

") The stars that were in this position on the ain se*uence have undergone splitting

into $inary stars and hence appear lower down on the diagra.#) This type of cluster contains only low-ass stars and has never had high-

luinosity stars on its ain se*uence.

Ans& A'ection& 1-11

1,.Which of the following stateents is NOT true of a glo$ular cluster?

A) (t has a round shape.B) (t can contain up to 1 illion stars.

") (t contains any ain-se*uence stars.

#) (t contains $oth high- and low-ass stars on the ain se*uence.

Ans& #'ection& 1-11

1/.Which of the following stateents is NOT true of a glo$ular cluster?

A) (t can contain up to 1 illion stars.

B) (t contains only low-ass stars on the ain se*uence.") (t does not contain ain-se*uence stars.

#) (t has a round shape.

Ans& "

'ection& 1-11

1.=ow do astronoers %now that glo$ular clusters are very old?

A) They do not contain any red giant stars.B) There are no ain-se*uence stars in glo$ular clusters.

") Their stars have a high a$undance of heavy eleents.

#) There are no assive ain-se*uence stars in glo$ular clusters.Ans& #

'ection& 1-11

15.At what stage of evolution are the horiEontal-$ranch stars+ those with siilar luinosities $etween > and 1>> ties that of the 'un+ $ut spread over a range of teperatures?

A) This region is part of the ain se*uence+ so these are in the ain-se*uence stage.

B) IreJain-se*uence stage+ evolving toward the ain se*uence") White-dwarf stage

#) IostJain-se*uence stage

Ans& #'ection& 1-11

16.=oriEontal-$ranch stars+ having a wide range of teperatures and luinosities $etween

> and 1>> ties that of the 'un+ are in what stage of their lives?

Page 1




A) 9ravitational contraction $efore the start of core hydrogen $urning

B) =ydrogen shell $urning+ with a degenerate heliu core

") "ore heliu $urning#) "ore hydrogen $urning

Ans& "

'ection& 1-11

1:.Which of the following stars are etal-rich?

A) Iopulation ( stars ") Iopulation (( starsB) ery old stars #) 9lo$ular cluster stars

Ans& A

'ection& 1-11

1<.=ow do the stars in a star cluster change with tie?

A) All stars in it evolve at the sae rate.

B) The stars with the greatest heavy-eleent content evolve the ost *uic%ly.

") The lowest-ass stars evolve the ost *uic%ly.#) The highest-ass stars evolve the ost *uic%ly.

Ans& #'ection& 1-11

>.What is the $est way to estiate the age of a star cluster?A) Ilot the stars on a =ertEsprung-ussell diagra and see which stars are still on the

ain se*uence.

B) easure the otions of the stars in the cluster and copare to theoretical odels.

") easure the heavy-eleent a$undance for the stars in the cluster.#) "ount the nu$er of T Tauri stars in the cluster.

Ans& A

'ection& 1-11

1.Of the following astronoical o$Fects or systes+ which is li%ely to $e the oldest?

A) A T Tauri star B) The Ileiades ") The 'un #) A glo$ular cluster Ans& #

'ection& 1-11

.The 'un is a e$er of which of the following groups of stars?A) "epheid varia$les ") =oriEontal $ranch stars

B) Iopulation (( #) Iopulation (

Ans& #'ection& 1-11

,.An astronoer plots the =- diagra of a star cluster and finds that it contains hot B-type stars on the ain se*uence and cooler 9- and 8-type stars noticea$ly a$ove the

ain se*uence. This cluster is

A) very young $ecause the 9 and 8 stars are still evolving toward the ain se*uence.

B) of indeterinate age since one cannot estiate the age of the cluster fro the

Page 2




inforation given.

") ipossi$le $ecause one cannot have cool stars a$ove the ain se*uence when hot

stars are on the ain se*uence.#) old $ecause the 9 and 8 stars are already evolving off 7away fro) the ain

se*uence.

Ans& A'ection& 1-11

/.(n the =- diagra shown in @igure 1-/$ of "oins and 8aufann+ Discovering theUniverse+ 6th 0d.+ the $rightest stars in the Ileiades cluster are not on the ain se*uence+

$ut away fro it toward the upper right. Why is this?

A) These stars have not yet reached the ain se*uence and are in the T Tauri phase.

B) These stars have already evolved through the red-giant phase and have nowreturned to the $lue-giant phase on their way to the white-dwarf phase.

") These stars have already $ecoe white-dwarf stars+ as shown $y their position.

#) These $lue supergiant stars have already $egun to evolve toward the red-supergiant

phase.Ans& #

'ection& 1-11

.What is the 3turnoff4 point for a star cluster?

A) The point in the =ertEsprung-ussell diagra occupied $y stars undergoing 7ora$out to undergo) the heliu flash

B) The point in the =ertEsprung-ussell diagra occupied $y the highest-ass ain-

se*uence stars in the cluster

") The point in the =ertEsprung-ussell diagra occupied $y the lowest-ass ain-se*uence stars in the cluster

#) The point in the =ertEsprung-ussell diagra occupied $y the highest-ass stars

that have not yet reached the ain se*uenceAns& B

'ection& 1-11

5.@or an astronoer+ what is the significance of the turnoff point in the =ertEsprung-

ussell diagra of a star cluster?

A) (t tells the astronoer the age of the star cluster.

B) (t tells the astronoer which stars ight $e a$out to e2plode as supernovae.") (t tells the astronoer which stars pulsate in $rightness 7varia$le stars).

#) (t tells the astronoer the etal content of the star cluster.

Ans& A'ection& 1-11

6.The age of a cluster can $e deterined $yA) carrying out a nu$er count of the stars in the cluster.

B) easuring its speed of otion relative to the 'un.

") deterining the turnoff point on the ain se*uence of its =ertEsprung-ussell

diagra.

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#) o$serving its position in the s%y with respect to the 'un.

Ans& "

'ection& 1-11

:.The age of a cluster of stars can $e Fudged $y

A) the aount of radioactive eleents detected on the surfaces of its stars.B) the turnoff point on the ain se*uence of its =ertEsprung-ussell diagra.

") the total nu$er of stars within the cluster.

#) the nu$er of novae per year occurring within the cluster.Ans& B

'ection& 1-11

<.'uppose that+ when the stars in a particular open star cluster are plotted in a =ertEsprung-ussell diagra+ the turnoff point is at an a$solute agnitude of Q,. What is the

appro2iate age of this cluster? 7'ee @igure 1-/+ "oins and 8aufann+ Discovering

the Universe+ 6th 0d.)

A) 1>> illion years B) >> illion years ") / $illion years #) 1 $illion yearsAns& "

'ection& 1-11

,>.The stars at the turnoff point in the =ertEsprung-ussell diagra of the =yades star

cluster have a luinosity of appro2iately 1> ties that of the 'un+ while those at theturnoff point in the cluster /1 have a luinosity of a$out :> ties that of the 'un. @ro

this inforation+ we can say with certainty that

A) the =yades cluster has ore stars in it than /1.

B) the =yades cluster is younger than /1.") the =yades cluster is farther away than /1.

#) the =yades cluster is older than /1.

Ans& #'ection& 1-11

,1.Which of the following stars are etal-poor?A) Open-cluster stars ") Iopulation (( stars

B) ery young stars #) Iopulation ( stars

Ans& "

'ection& 1-11

,.'tars are fored fro interstellar atter. Why then are stars in open clusters etal-rich+

while stars in glo$ular clusters are etal-poor?A) Because open clusters contain very hot stars that produce etals $y nuclear

reactions in their outer layers

B) Because glo$ular clusters have 3$urned4 their heavy eleents over their longerlifetie

") Because glo$ular clusters are too young for their stars to have produced any

significant aount of etals

#) Because open clusters are young and stars have fored fro aterial that has $een

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enriched in etals $y supernova e2plosions of previous stars

Ans& #

'ection& 1-11

,,.The spectru of stars in an open cluster is found to contain spectral lines fro any

heavy eleents+ these stars $eing %nown as 3etal-rich.4 What is the source of theseheavy eleents?

A) The fusion reactions on the very hot surfaces of these stars

B) The heavy eleent content of these stars is not enhanced $ut the hydrogen andheliu content has $een depleted $y intense stellar winds ade up preferentially of

these light eleents.

") The fusion reactions in the star cores+ carried to the surface $y convection

#) The interstellar ediu+ which originated in e2plosions of stars earlier in historythat had anufactured heavy eleents $y nuclear fusion

Ans& #

'ection& 1-11

,/.Which of the following stars would you classify as a population (( star?

A) A star with very low a$undance of heavy eleentsB) Any e$er of an open star cluster

") A star with appro2iately the sae a$undance of heavy eleents that we find in

the 'un#) A star with uch higher a$undance of heavy eleents than we find in the 'un

Ans& A

'ection& 1-11

,.(n connection with a star+ what does the phrase 3etal-poor4 ean?

A) (t has a low a$undance of all eleents heavier than hydrogen in its spectru.

B) (t has a low a$undance of all eleents heavier than hydrogen and heliu in itsspectru.

") (t has a low a$undance of all eleents in its spectru.

#) (t ight or ight not have a low a$undance of car$on in its spectru $ut isdefinitely wea% in iron.

Ans& B

'ection& 1-11

,5.When a starDs evolutionary trac% in the =ertEsprung-ussell diagra carries it into the

insta$ility strip+ what happens to the star?

A) (t pulsates randoly in $rightness. ") (t e2plodes.B) (t collapses and fors a $lac% hole. #) (t pulsates regularly in $rightness.

Ans& #

'ection& 1-1

,6.What are the stars in the upper part of the insta$ility strip called?

A) Irotostars B) T Tauri stars ") !yrae varia$les #) "epheid varia$les

Ans& #

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'ection& 1-1

,:.What are the stars in the lower part of the insta$ility strip called?A) T Tauri stars B) Irotostars ") "epheid varia$les #) !yrae varia$les

Ans& #

'ection& 1-1

,<. !yrae stars are

A) pulsating stars that vary regularly+ all with periods of less than one day.B) rotating neutron stars with very rapid and regular $rightness fluctuations.

") eclipsing $inary stars.

#) pulsating stars that vary irregularly+ with periods of several hundred days.

Ans& A'ection& 1-1

/>.What is a "epheid varia$le star?

A) One of several classes of stars that pulsate randoly in $rightnessB) A low-ass+ horiEontal-$ranch star that pulsates regularly in $rightness

") A star that norally reains constant in $rightness $ut occasionally flares up in $rightness $y several agnitudes

#) A high-ass star that pulsates regularly in $rightness

Ans& #'ection& 1-1

/1."epheid stars are

A) giant stars that pulsate in $rightness+ siEe+ and teperature.B) white dwarf stars+ late in their evolutionary life.

") e$ers of $inary systes+ in which one star periodically eclipses the other.

#) stars at an early stage in stellar evolution+ preJain-se*uence.Ans& A

'ection& 1-1

/.A "epheid varia$le

A) is a type of eclipsing $inary star.

B) is a high-ass giant or supergiant star that pulsates regularly in siEe and $rightness.

") is a low-ass red giant that varies in siEe and $rightness in an irregular way.#) is a varia$le eission ne$ula near a T Tauri star.

Ans& B

'ection& 1-1

/,.What scientific ethod is used to o$serve the pulsation in siEe of a "epheid varia$le star?

A) This $ehavior has only $een predicted theoretically and has never $een detected.B) The o$served pertur$ations in the or$its of planets around these stars

") The o$served increase and decrease in the siEe of the starDs iage

#) #oppler shift of a$sorption lines in its spectru

Ans& #

Page "




'ection& 1-1

//.What characteristic of "epheid varia$les a%es the e2treely useful to astronoers?A) Their a$solute agnitude is related directly to their period of pulsation.

B) Their a$solute agnitude is directly related to their diaeter.

") Their a$solute agnitude is related directly to their etal content 7heavy eleenta$undance).

#) Their a$solute agnitude is related directly to their surface teperature.

Ans& A'ection& 1-1,

/.The period of varia$ility of a "epheid varia$le star+ which is easily easured+ is directly

related to which stellar paraeter+ there$y providing a relia$le ethod for theeasureent of distance to stars?

A) !uinosity ") 'urface teperature

B) elocity away fro the 0arth #) 'urface agnetic field

Ans& A'ection& 1-1,

/5.What is the ost iportant use of "epheid varia$les for astronoers?

A) The distance to a "epheid varia$le can $e found very easily.

B) The characteristics of the pulsation of a "epheid varia$le can $e used to investigateconditions in the core of the star.

") The diaeter of a "epheid varia$le can $e found very easily.

#) The etal content of a "epheid varia$le can $e found very easily.

Ans& A'ection& 1-1,

/6.Which of the following aFor pertur$ations can occur to a close $inary syste andradically alter the evolution and $ehavior of the two individual stars?

A) The heating of the localiEed areas of the atosphere of one star $y its copanion

B) The transfer of atter fro one star to its copanion") The gravitational distur$ance of one starDs otion $y its copanion+ forcing it to

ove in an or$it

#) The eclipsing of the light fro one star $y the other when viewed fro the 0arth

Ans& B'ection& 1-1/

/:.What particular and very iportant phenoenon fre*uently occurs in $inary star systeswhere the stars are very close together?

A) The radiation fro the hotter star will slowly heat and evaporate away the cooler

star.B) ass lost fro one star is deposited on its copanion.

") The less assive star+ in its elliptical or$it+ will repeatedly pass through the thin+

e2tended atosphere of the second star+ producing periodic rises and falls in light

output fro the star syste.

Page #




#) The less assive star spirals slowly into its ore assive copanion $ecause of

tidal interactions.

Ans& B'ection& 1-1/

/<.The shape of the cross-section of the oche lo$es around a close $inary star syste+ta%en through the centers of $oth stars+ is

A) two une*ual ellipses that touch at the center of the lo$es.

B) a sphere centered on the center of ass of the star syste.") an ellipse with a star at each focus.

#) a figure eight.

Ans& #

'ection& 1-1/

>.The transfer of ass fro the surface of one star onto the surface of another is ost often

o$served in

A) detached $inaries. ") contact $inaries.B) overcontact $inaries. #) seidetached $inaries.

Ans& #'ection& 1-1/

1.(n soe $inary star systes+ such as Algol+ the less assive star is an old red giant starand the ore assive star is on the ain se*uence. This is evidence that

A) the ore assive star captured the other one into or$it soe tie after the two

stars had fored.

B) the ore assive star fored later+ fro a dis% of gas surrounding the less assivestar.

") ass transfer has occurred fro one of the stars to the other.

#) stars evolve differently in $inary star systes+ with less assive stars evolvingfaster than ore assive stars.

Ans& "

'ection& 1-1/

.(n soe $inary star systes+ such as β !yrae+ essentially no light is seen fro the ore

assive star. This is $ecause

A) the ore assive star is hidden $y an accretion dis% of aterial fro the lessassive star.

B) the or$it of the ore assive star %eeps it hidden $ehind the larger $ut less assive

star as seen fro the 0arth.") the ore assive star is a $lac% hole fro which light cannot escape.

#) the ore assive star is still hidden in the dust clouds fro which it fored.

Ans& A'ection& 1-1/

,.Which factor+ ore than any other+ odifies the evolutionary trac%s of stars in $inary

co$inations copared to their single-star counterparts?

Page $




A) Tidal distortion of the shapes of the stars

B) eduction of the *uantu echanical liitation on continued shrin%ing of one star

$y the gravitational field of the second star ") ass e2change $etween the stars

#) adiation fro one star heating the surface of the second star

Ans& "'ection& 1-1/

/.What is a oche lo$e?A) The iaginary $oundary around each star in a close $inary syste encopassing

the ass gravitationally $ound to that star

B) The iaginary $oundary around each star in a close $inary syste that ar%s the

liit outside of which planets cannot for") The iaginary $oundary around each star in a close $inary syste that ar%s the

liit inside of which planets cannot for $ecause they would $e torn apart $y the

starDs gravity

#) The iaginary $oundary around each star in a close $inary syste that ar%s theliit of each starDs gravitational pull& as long as each star is within its own oche

liit the stars will have no effect on each other Ans& A

'ection& 1-1/

.The coponents of a $inary star+ particularly if they are close+ can influence each other in

various ways. Which of the following is NOT li%ely to $e an effect of one star on its

copanion?

A) A very hot star can heat part of its cooler copanion to produce a hot spot.B) The gravitational force of one star will a%e its copanion ove in an or$it+ rather

than reaining stationary.

") (ntense radiation fro a hot star can produce nuclear reactions on the surface of acooler copanion and initiate a nova e2plosion.

#) ass can $e transferred fro one star to its copanion.

Ans& "'ection& 1-1/

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Astronomy - Chapter 12 Test