Astronomy - Chapter 11 Test

8/10/2019 Astronomy - Chapter 11 Test

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CHAPTER 11: Characterizing Stars

1.We are about 8000 parsecs from the center of our Milky Way Galaxy, and the smallest

parallax angle we can measure from orbiting obseratories is about 0.001 arcseconds.

!ow far toward the galactic center can we see with this techni"ue #ignoring galactic dustand other obstacles$%

&$ &ll the way to the center

'$ &bout half way to the center ($ &bout one)eighth of the way to the center

*$ +nly 0.008 1-1/ of the way to the center

&ns (ection 11)1

.!ow far away is the nearest star beyond the un%

&$ &bout 1-2 ly away ($ &bout 2 ly away'$ &bout 1-10 ly away *$ 'etween 1 and ly away

&ns (

ection 11)1

3.!ow far away is the nearest star beyond the un, in parsecs%

&$ 'etween 1 and pc away ($ &bout 2 pc away'$ &bout 1 pc away *$ 'etween 1- and 1 pc away

&ns &

ection 11)1 and 4oolbox 11)1

2.What is parallax%

&$ 4he distance to an ob5ect, measured in parsecs

'$ 4he angle taken up by the si6e #e.g., diameter$ of an ob5ect, as seen by an obserer ($ 4he shift in angular position of an ob5ect as it moes in space

*$ 4he apparent shift in position of an ob5ect as the obserer moes&ns *ection 11)1

/.7n what fundamental way do we #and many other animals$ utili6e parallax for themeasurement of distance%

&$ +ur eyes focus back and forth continuously, and the brain interprets this focusing in

terms of distance to the ob5ect iewed.

'$ 4he eye can measure the time taken for light to trael from an ob5ect, and the braininterprets this in terms of distance to the ob5ect iewed.

($ We are always moing our heads slightly from side to side, and the brain compares

look angles from each of these positions to obtain the distance to the ob5ect iewed.*$ +ur eyes are mounted hori6ontally about 10 cm apart in our heads, and the brain

interprets the relatie look angles of these eyes in terms of distance to the ob5ect

iewed.&ns *

ection 11)1

.tellar parallax is&$ the inferred change in the distance to a star as its light is dimmed by passing

through an interstellar cloud.

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'$ the apparent shift seen in the position of a nearby star against more distant stars as

we orbit the un.

($ the difference between the apparent and absolute magnitudes of a star.*$ the circular or elliptical motion of a star in a binary system as the two stars orbit

each other.

&ns 'ection 11)1

9.&s you drie along a road, trees in the middle distance seem to shift in position relatie tofar)away hills. What name is gien to this phenomenon%

&$ :arallax '$ :erspectie ($ 4he *oppler effect *$ 4he inerse)s"uare law

&ns &

ection 11)1

8.4he motion that is used to change the position of the obserer in the most common

parallax measurements of distances to relatiely nearby stars is

&$ the motion of the un around the galactic center.'$ the change in latitude of the obseration point on the ;arth.

($ the motion of the ;arth in its orbit around the un.*$ the rotation of the ;arth on its axis.

&ns (

ection 11)1

<.!ow many stars #other than the un$ hae an angle of parallax greater than one second of

arc%

&$ &bout 100 '$ Millions ($ =one *$ +nly one&ns (

ection 11)1

10.!ow is stellar parallax of a star defined%

&$ 7t is the angle taken up by the diameter of a star as seen from the ;arth.

'$ 7t is the angle subtended by the radius of the ;arth>s orbit as seen from the star.($ 7t is the angle subtended by the diameter of the ;arth>s orbit as seen from the star.

*$ 7t is the angle through which a star moes in our sky oer the course of 1 year due

to the motion of both the star and the ;arth.

&ns 'ection 11)1

11.:arallax of a nearby star is used to estimate its&$ surface temperature. ($ apparent magnitude.

'$ distance from the ;arth. *$ physical si6e or diameter.

&ns 'ection 11)1

1.Which of the following properties of a nearby star is determined by a measurement of

stellar parallax%

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&$ 7ts spectral type and surface temperature

'$ 7ts rotation period

($ 7ts apparent magnitude*$ 7ts distance from the ;arth

&ns *

ection 11)1

13.4he most straightforward way to determine the distance to a nearby star inoles the

measurement of &$ its spectrum.

'$ the ratio of apparent and absolute magnitudes.

($ the ?eeman effect of spectral lines in its spectrum.

*$ its stellar parallax.&ns *

ection 11)1

12.!ow can we tell that some stars are relatiely close to us in the sky%&$ 'ecause they appear to moe periodically back and forth against the background

stars because of the ;arth>s moement around the un'$ 'ecause they appear to be extremely bright and must therefore be ery close to us

($ 'ecause they are occasionally occulted or eclipsed by our Moon, hence they must

be close*$ 'ecause the light from these stars shows only a ery small redshift caused by the

uniersal expansion of the unierse, so they must be close

&ns &

ection 11)1

1/.tellar parallax appears because

&$ the ;arth rotates about its own axis.'$ stars moe in space.

($ stars hae finite si6e #i.e., they are not really 5ust points of light$.

*$ the ;arth moes in space.&ns *

ection 11)1

1.Who was the first person to measure the parallax of a star successfully%&$ ir George &iry in ;ngland

'$ !enry =orris @ussell in the Anited tates

($ 4ycho 'rahe in *enmark *$ Briedrich Wilhelm 'essel in Germany

&ns *

ection 11)1

19.4he most accurate stellar parallax measurements for distances to the ma5ority of stars in

our neighborhood of the unierse hae been made by

&$ the !ubble pace 4elescope.

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'$ 'essel, in 1838, since no measurements since then hae matched his precision.

($ the !ipparchos satellite.

*$ the Cery Dong 'aseline &rray of radio telescopes.&ns (

ection 11)1

18.What is the relationship between stellar parallax # p$ measured in seconds of arc and

distance #d $ measured in parsecs%

&$ d 1- p '$ d 1- p ($ d p *$ d p

&ns '


1<.& particular star has an angle of parallax of 0. arcsecond. What is the distance to thisstar%

&$ /0 pc '$ pc ($ / pc *$ 0. pc

&ns (


0.& star is 80 pc from the un. 7ts apparent motion against the background sky as a resultof the ;arth>s motion through 1 &A, that is, its stellar parallax, is

&$ 0.01/ arcsecond. ($ 0.01/ radian, or 0.9E.

'$ 0.01/ arcminute. *$ 80 arcseconds.&ns &


1.& particular star has an angle of parallax of 0.1 arcsec. What is the distance to this star%&$ &bout 10 ly '$ &bout 33 ly ($ &bout 0.1 ly *$ &bout 3.3 ly

&ns '


.& particular star is 0 pc away from the ;arth. What is the stellar parallax for this star%

&$ arcsec '$ 0 arcsec ($ 0.0 arcsec *$ 0.0/ arcsec&ns *


3.7f stellar parallax as small as 0.01 arcsec can be measured using telescopes on the ;arthto obsere stars, to what distance does this correspond in space%

&$ /00 pc '$ 00 pc ($ 0.01 pc *$ 100 pc

&ns *ection 11)1 and 4oolbox 11)1

2.7f a nearby star shows a parallax of 0./ arcsec #when the ;arth moes through 1 &A, bydefinition$ at what is its distance from the ;arth, in light)years%

&$ ly '$ 1.83 ly ($ ./ ly *$ 3. ly

&ns (


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/.4he triple star system α (entauri has a parallax #the largest known$ of 0.9/ arcsec. !ow

far is this star system from the un in light)years% #(areful with unitsF$&$ 2.3/ ly '$ 0.21 ly ($ 1.33 ly *$ 0.9/ ly

&ns &


.7f the !ipparchos satellite measures the parallax motion of a star against the background

stars and concludes that the star has a parallax of 0.002 arcsec, how far is that star fromus%

&$ /pc or 81./ ly ($ 200pc or 1300 ly

'$ /0 pc or 81/ ly *$ 0.002 pc or 0.013 ly

&ns 'ection 11)1 and 4oolbox 11)1

9.!ow far out into space can we determine stellar distances using telescopes on the ;arth if

we can only measure stellar parallax alues as small as 0.01 arcsec%&$ 10 pc '$ 100 pc ($ /00 pc *$ 000 pc


8.4he semima5or axis of :luto>s orbit is almost 20 &A. 4he smallest parallax angle we canmeasure from orbiting obseratories is about 0.001 arcsec. uppose we use this

techni"ue to measure parallax from :luto>s orbit #oer the course of half a :luto yearH$.

What is the maximum distance we could measure%

&$ 20 pc '$ 1000 pc ($ 20,000 pc *$ 80,000 pc&ns (

ection 11)1

<.!ow much can we learn about a star from a measurement of its apparent magnitude%

&$ 4he intrinsic brightness of a star #the total light actually emitted by the star$

'$ 4he brightness the star would appear to hae if it were exactly 10 pc from the ;arth($ 4he brightness of a star as it appears in our sky

*$ 4he total output of electromagnetic energy emitted at all waelengths from the star

&ns (

ection 11)

30.&pparent magnitude is a measure of

&$ the intrinsic brightness #actual light output$ of a star.'$ the si6e #diameter$ of a star.

($ the temperature of a star.

*$ the brightness of a star, as seen from the ;arth.&ns *

ection 11)

31.4he relatie brightness of stars as we see them in our sky is represented by their

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&$ absolute magnitudes. ($ surface temperatures.

'$ apparent magnitudes. *$ luminosities.

&ns 'ection 11)

3.& star of apparent magnitude I1 appears&$ either brighter or fainter than a star of apparent magnitude I, depending on the

distance to the stars.

'$ farther away than a star of apparent magnitude I.($ brighter than a star of apparent magnitude I.

*$ fainter than a star of apparent magnitude I.

&ns (

ection 11)

33.& star of apparent magnitude I/ appears

&$ fainter than a star of apparent magnitude I3.

'$ farther away than a star of apparent magnitude I3.($ brighter than a star of apparent magnitude I3.

*$ either brighter or fainter than a star of apparent magnitude I3, depending on thedistance to the stars.

&ns &

ection 11)

32.& star of apparent magnitude I2.9 appears

&$ brighter than a star of apparent magnitude I2.8.

'$ either brighter or fainter than a star of apparent magnitude I2.8, depending on thedistance to the stars.

($ farther away than a star of apparent magnitude I2.8.

*$ fainter than a star of apparent magnitude I2.8.&ns &

ection 11)

3/.& star of apparent magnitude I3./ appears

&$ farther away than a star of apparent magnitude I3.3.

'$ fainter than a star of apparent magnitude I3.3.

($ either brighter or fainter than a star of apparent magnitude I3.3, depending on thedistance to the stars.

*$ brighter than a star of apparent magnitude I3.3.

&ns 'ection 11)

3.& star of apparent magnitude J appears&$ fainter than a star of apparent magnitude J3.

'$ brighter than a star of apparent magnitude J3.

($ farther away than a star of apparent magnitude J3.

*$ either brighter or fainter than a star of apparent magnitude J3, depending on the

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distance to the stars.

&ns &

ection 11)

39.& star of apparent magnitude J1./ appears

&$ farther away than a star of apparent magnitude I.0.'$ fainter than a star of apparent magnitude I.0.

($ brighter than a star of apparent magnitude I.0.

*$ either brighter or fainter than a star of apparent magnitude I.0, depending on thedistance to the stars.

&ns (

ection 11)

38.& star of apparent magnitude I.1 appears

&$ farther away than a star of apparent magnitude J1..

'$ fainter than a star of apparent magnitude J1..

($ brighter than a star of apparent magnitude J1..*$ either brighter or fainter than a star of apparent magnitude J1., depending on the

distance to the stars.&ns '

ection 11)

3<.4he ancient Greek astronomer !ipparchus introduced the magnitude scale on which he

called the brightest stars first magnitude. 4oday, the brightest star in the night sky is

irius, with a magnitude of J1.2. 4his is considerably brighter than first magnitude.

Why the discrepancy%&$ irius was formed since the era in which !ipparchus lied.

'$ irius existed during !ipparchus> lifetime, but it has obiously brightened

considerably since then.($ !ipparchus had poor eyesight and made many classification errors.

*$ &fter using modern scientific instruments to measure the actual energy output of

stars, astronomers modified the magnitude scale of !ipparchus.&ns *

ection 11)

20.4he statement that the apparent magnitude of a ariable star has increased indicates that&$ its brightness has increased.

'$ its surface temperature has decreased.

($ its brightness has decreased.*$ its surface temperature has increased.

&ns (

ection 11)

21.'y approximately how many magnitudes is the star irius fainter than the full Moon in

our sky% #ee Big. 11), (omins and Kaufmann, Discovering the Universe, 9th ;d.$

&$ 1/ '$ ($ 11 *$ /

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&ns (

ection 11)

2.& star that has an apparent magnitude of 0 #see Big. 11), (omins and Kaufmann,

Discovering the Universe, 9th ;d.$

&$ would be fainter than pica #alpha Cirginis$, which has an apparent magnitude ofI1.0.

'$ would be brighter than *eneb #alpha (ygni$, which has an apparent magnitude of

I1..($ would hae infinite brightness, since 1-0 infinity.

*$ would not be emitting any light, and therefore could not be seen from the ;arth.

&ns '

ection 11)

23.4he star &lphard has an apparent magnitude of .0, and the star Megre6 has an apparent

magnitude of 3.3. 4he only thing that can be said with certainty about &lphard is that

&$ it is brighter than Megre6, as seen in our sky.'$ it has a greater luminosity than Megre6.

($ it is fainter than Megre6, as seen in our sky.*$ it is closer than Megre6.

&ns &

ection 11)

22.& star>s absolute magnitude and its apparent magnitude hae the same numerical alue.

!ow far is this star from the ;arth%

&$ 7t is not possible for a star to hae the same absolute and apparent magnitudes.'$ 7t would hae to be an infinite distance away.

($ 10 ly

*$ 10 pc&ns *

ection 11)3

2/.What is the ratio of the brightnesses of two stars if their apparent magnitudes differ by

I1%

&$ &bout ./ '$ 100 ($ , by definition *$ 10

&ns &ection 11)3 and 4oolbox 11)

2.4wo stars whose apparent magnitudes differ from each other by fie magnitudes hae aratio of brightnesses of

&$ /. '$ 10. ($ 100. *$ ./.

&ns (ection 11)3 and 4oolbox 11)

29.!ow many times brighter than a magnitude I2.0 star is a magnitude I3.0 star%

&$ 100 times brighter

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'$ 4wice as bright

($ & factor of 2-3, or 1.333 times, brighter

*$ ./1 times brighter &ns *

ection 11)3 and 4oolbox 11)

28.!ow many times brighter is a star with an apparent magnitude of I1.0 than a star with an

apparent magnitude of I.0%

&$ 100 times brighter '$ / times brighter

($ 4he "uestion is incorrectly wordedL the magnitude I star will be 100 times

brighter than the magnitude I1 star.

*$ ./1 times brighter.&ns &


2<.4he un>s luminosity is 3.83 10

watts. 'y the time this energy reaches the ;arth, ithas spread out so that it proides only 1390 Watts to each s"uare meter. 4he orbit of

Mars has a mean radius of 1./3 &A. !ow many watts of the un>s luminosity are proided to each s"uare meter of the surface of Mars%

&$ 32 '$ 1/3 ($ /8/ *$ 1/98

&ns (ection 11)3

/0.!ow many nd)magnitude stars would be needed in a close cluster to match the light

intensity of a 1st)magnitude star%&$ &bout ./ '$ ($ &bout 10 *$ &bout 0.2, or 1-./

&ns &


/1.!ow many stars of th magnitude in a small cluster would it take for the cluster to appear

as bright as a single 1st)magnitude star%&$ 10/ '$ / ($ *$ 100

&ns *


/.7f a distant cluster were to be composed only of stars with apparent magnitude of I3, how

many of these stars would there be in this cluster if its apparent magnitude matched that

of a star with apparent magnitude of I1%&$ '$ 10, or 100 ($ &bout ./ *$ 'etween and 9

&ns *


/3.irius, isually the brightest star in our sky, has an apparent magnitude of about J1./

while the &ndromeda Galaxy has an apparent magnitude of about I3./. What is the ratio

of their brightnesses, as seen by ;arth)bound obserers%

Page 9




&$ 4he &ndromeda Galaxy is 100 times brighter than irius.

'$ 4he &ndromeda Galaxy is times fainter than irius.

($ 4he &ndromeda Galaxy is / times brighter than irius.*$ 4he &ndromeda Galaxy is 100 times fainter than irius.

&ns *


/2.What is the fundamental difference between absolute and apparent magnitude of a star%

&$ I/, since absolute and apparent magnitude differ by this alue, by definition'$ &pparent magnitude depends on the star>s temperature, whereas absolute magnitude

is independent of temperature.

($ &pparent magnitude depends on the si6e of the star, whereas absolute magnitude is

independent of this parameter.*$ &bsolute magnitude is an intrinsic property of the star, whereas apparent magnitude

depends on its distance from the ;arth.

&ns *


//.Dight leaing a point source spreads out so that the apparent brightness I of light per unit

area aries with distance d according to which of the following laws #µ means

proportional toH$%

&$ I constant '$ I µ 1-d ($ I µ d *$ I µ 1-d

&ns 'ection 11)3

/.uppose that, at night, the distance between an obserer and a light bulb is doubled. !ow

will its final brightness compare to its initial brightness%

&$ 7t will appear 1-1 as bright. ($ 7t will appear 1- as bright.'$ 7t will appear 2 times brighter. *$ 7t will appear 1-2 as bright.

&ns *ection 11)3

/9.uppose that two identical stars #haing the same total light output$ are located such thatstar & is at a distance of / pc and star ' is at a distance of / pc. !ow will star ' appear,

compared to star &%

&$ tar ' will be 1-/ as bright as star &.

'$ tar ' will be 1-/ as bright as star &.($ tar ' will be 1-. as bright as star &.

*$ tar ' will be 1-0 as bright as star &.&ns 'ection 11)3

/8.4wo stars, : and N, can be seen in the same region of our sky with the same apparentmagnitude, but star N is twice as far away as star :. What is the ratio of the intrinsic

brightnesses #luminosities$ of these stars #star :-star N$%

&$ 2 '$ ($ 1-2 *$ 1-

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&ns (

ection 11)3

/<.4he intensity of sunlight per s"uare meter reaching Oupiter is approximately what fraction

of that at the ;arth>s orbital distance% #Bor orbital radii see &ppendix, 4able &)1, (omins

and Kaufmann, Discovering the Universe, 9th ;d.$&$ / times '$ &bout the same ($ 1-/ *$ 1-/

&ns *

ection 11)3

0.What is the intensity of sunlight per s"uare meter reaching Cenus compared with this

intensity at the ;arth>s orbital distance% #Bor orbital radii see &ppendix, 4able &)1,

(omins and Kaufmann, Discovering the Universe, 9th ;d.$&$ &bout the same, since this intensity remains constant, following a law of nature

'$ &bout 1.2

($ &bout 1.<

*$ &bout 0./&ns (

ection 11)3

1.!ow much more light falls on a unit area of Mercury>s surface than on an e"uialent area

of the Moon if Mercury is at 0.2 &A and the ;arth>s Moon is at 1.0 &A from the un%&$ 0.2 '$ ./ ($ ./ *$ 0.1

&ns '

ection 11)3

.4he star α (entauri ( and the star Groombridge 32 ' hae the same apparent magnitude,

but α (entauri ( is 1.3 pc away from the ;arth and Groombridge 32 ' is 3./ pc away.What is the luminosity of Groombridge 32 ', compared to α (entauri (% #ee Big. 11)3,

(omins and Kaufmann, Discovering the Universe, 9th ;d.$&$ .9 times brighter ($ .9 times fainter

'$ 9. times fainter *$ 9. times brighter

&ns *ection 11)3

3.&bsolute magnitude is defined as the apparent magnitude that a star would hae if

&$ all of the energy from the star were concentrated in the isual region.'$ it were located at exactly 10 ly from the ;arth.

($ it were located at exactly 10 pc from the ;arth.*$ it were located at exactly 10 &A from the ;arth.

&ns (

ection 11)3

2.4he absolute magnitude of a star is the brightness the star would appear to hae if it were

placed at what distance from the ;arth%

&$ 3. ly '$ 4he distance to the galactic center ($ 10 ly *$ 1 &A

Page 11




&ns &

ection 11)3

/.7f we restrict our measurements to a specific band of color or waelength using an optical

filter, what obserations are necessary in order to determine the absolute magnitude of a

star at this color%&$ 7ts distance and its temperature

'$ 7ts apparent magnitude and its temperature

($ Oust a measurement of its apparent magnitude, since its absolute magnitude issimply apparent magnitude I /

*$ 7ts apparent magnitude and its distance

&ns *


.4he un has an absolute magnitude of I2.8. !ow far away would we hae to go in order

for the un to be 5ust barely isible to the naked eye #th magnitude$%

&$ 1. pc '$ pc ($ 19.2 pc *$ .2 pc&ns (

ection 11)3 and textbox 11)3

9.& particular star is at a distance of 0 pc from the ;arth. Bor this star, the apparent

magnitude will hae&$ a larger alue than its absolute magnitude.

'$ a smaller alue than its absolute magnitude.

($ the same alue as its absolute magnitude, since magnitude is independent of

distance.*$ a larger or a smaller alue than the absolute magnitude, depending on the

temperature and diameter of the star.

&ns &ection 11)3

8.& particular star is at a distance of / pc from the ;arth. Bor this star, the apparentmagnitude will hae

&$ the same alue as its absolute magnitude, since magnitude is independent of

distance.

'$ a smaller alue than its absolute magnitude.($ a larger or smaller alue than its absolute magnitude, depending on the temperature

and diameter of the star.

*$ a larger alue than its absolute magnitude.&ns '

ection 11)3

<.4he star &lderamin has an apparent magnitude of .2 and an absolute magnitude of 1.2.

Brom this information #assuming that the starlight has not been dimmed by interstellar

clouds$ we can say for sure that

&$ &lderamin is less than 10 pc away. ($ &lderamin is more than 10 ly away.

Page 12




'$ &lderamin is less than 10 ly away. *$ &lderamin is more than 10 pc away.

&ns *

ection 11)3

90.4he star Bomalhaut has an apparent magnitude of 1.1/ and an absolute magnitude of .0.

Brom this information #assuming that the starlight has not been dimmed by interstellarclouds$ we can say for sure that Bomalhaut is

&$ more than 10 ly away. ($ less than 10 ly away.

'$ less than 10 pc away. *$ more than 10 pc away.&ns '

ection 11)3

91.4he star &lderamin has an apparent magnitude of .2 and an absolute magnitude of 1.2.4he star Merak has an apparent magnitude of .2 and absolute magnitude of 0./.

&ssuming that neither star has been dimmed by interstellar clouds, we can say for sure

that

&$ Merak and &lderamin are the same distance from us.'$ Merak is farther away from us than &lderamin.

($ Merak is an intrinsically fainter star than &lderamin.*$ Merak is closer to us than &lderamin.

&ns '

ection 11)3

9.4he star γ :hoenicis has an apparent magnitude of I3.2 and an absolute magnitude of J

2.. 4he =orth tar #:olaris$ has an apparent magnitude of I.0 and an absolute

magnitude of J2.. &ssuming that no light has been absorbed or scattered by interstellardust, we can say for sure that

&$ both stars are the same distance away from us.'$ :olaris is closer to us than γ :hoenicis.

($ :olaris is farther away from us than γ :hoenicis.

*$ :olaris appears fainter in our sky than γ :hoenicis.

&ns '

ection 11)3

93.& particular star has an apparent magnitude of I1 and an absolute magnitude of I/.

&ccording to the e"uation in &stronomer>s 4oolbox 11)3, (omins and Kaufmann,

Discovering the Universe, 9th ;d., what is the distance to this star%&$ 1/ pc '$ /0 pc ($ 1/ ly *$ /0 ly


92.& star whose absolute magnitude M is I. is seen to hae an apparent magnitude when

iewed from the ;arth of I/.. &ccording to the e"uation in &stronomer>s 4oolbox 11)3,

(omins and Kaufmann, Discovering the Universe, 9th ;d., how far away is the star%&$ 20 pc '$ 1.3 pc ($ 130 pc *$ 3-/, or 0. pc

&ns &

Page 13





9/.& star whose distance from the ;arth is 100 pc has an apparent magnitude of m I./.&ccording to the e"uation in &stronomer>s 4oolbox 11)3, (omins and Kaufmann,

Discovering the Universe, 9th ;d., what is its absolute magnitude%

&$ J9./ '$ I9./ ($ J./ *$ J29./&ns (


9.4he star &rietis has an apparent magnitude of I.9 and a distance of / ly. &ccording to

the e"uation in &stronomer>s 4oolbox 11)3, (omins and Kaufmann, Discovering the

Universe, 9th ;d., what is its absolute magnitude%

&$ I1.9 '$ J0.< ($ I. *$ I3.9&ns &


99.What is a star>s luminosity%&$ 4he amount of energy receied per second on one s"uare meter of a planet>s

surface, exactly 1 &A from the star '$ 4he total energy emitted by the star into all space per second, measured in watts

($ 4he apparent magnitude the star would hae if it were located exactly 10 ly from

the ;arth*$ 4he apparent magnitude the star would hae if it were located exactly 10 pc from

the ;arth

&ns '

ection 11)3

98.4he luminosity of a star is

&$ its brightness as seen by people on the ;arth.'$ its brightness if it were to be at a distance of 10 pc #3. ly$ from the ;arth.

($ its total energy output into all space.

*$ another name for its color or surface temperature.&ns (

ection 11)3

9<.4he luminosity of a star is a uni"ue measure of its&$ total energy output. ($ temperature.

'$ elocity of recession away from us. *$ physical si6e.

&ns &ection 11)3

80.4he un>s absolute magnitude is about I/. 4he brightest stars in our sky hae absolutemagnitudes of about J10. What is the luminosity of these stars compared to that of the

un, assuming that they hae similar spectral light distributions%

&$ 1 million times less ($ 1 million times greater

'$ / times less *$ 1/ times greater

Page 14




&ns (

ection 11)3

81.4wo stars in our sky hae the same apparent brightness. 7f neither of them is hidden

behind gas or dust clouds, then we know that

&$ they must be at the same distance from us.'$ they may be at different distances, in which case the nearer one must hae the

greater luminosity.

($ they may be at different distances, in which case the farther one must hae thegreater luminosity.

*$ they must hae the same temperature.

&ns (

ection 11)3

8.!ow bright #in absolute magnitude$ are the intrinsically brightest stars in the unierse%

&$ I19 '$ I1 ($ 0 *$ J10

&ns *ection 11)3

83.!ow bright #in absolute magnitude$ are the intrinsically faintest stars in the unierse%

&$ I1 '$ I19 ($ J10 *$ 0

&ns 'ection 11)3

82.7f the intrinsically brightest stars in our sky hae absolute magnitudes of J10, how bright

#in terms of total energy output per second$ are these stars compared to that of our un,whose absolute magnitude is I 2.8%

&$ &bout 12.8 times brighter

'$ &bout 800,000 times brighter ($ &bout 8000 times brighter

*$ &bout 101/, or 1,000,000,000,000,000, times brighter

&ns 'ection 11)3

8/.7f the intrinsically faintest stars in our sky hae absolute magnitudes of I19, how does

their total energy output compare to that of the un, whose absolute magnitude is I2.8%&$ &bout 1. times lower

'$ &bout 101, or 1,000,000,000,000, times lower

($ &bout 900 times lower *$ &bout 9,000 times lower

&ns *

ection 11)3

8.Which two fundamental parameters are most often used to place a particular star on a

path of stellar eolution for comparison with theoretical models%

&$ &pparent magnitude and distance

Page 15




'$ &pparent magnitude and temperature

($ Duminosity, or total energy output, and distance

*$ Duminosity, or total energy output, and temperature&ns *

ection 11)2

89.4he techni"ue called photometry in stellar astronomy is the measurement of

&$ the arrial times of photons from ariable and pulsating stars, in order to determine

accurately the pulsation or rotation periods of these stars.'$ the intensity of light from stars through seeral limited)bandpass filters from which

surface temperature, ariability, luminosity, etc., of stars can be determined.

($ the relatie absorption of light by different atoms and molecules in high)resolution

spectra of starlight, from which stellar temperatures can be estimated.*$ the precise positions and relatie motions of stars in the Galaxy, from which

galactic structure and oerall rotation can be determined.

&ns '

ection 11)2

88.&n astronomer is measuring the brightness of a particular star through a telescope, usingdifferent filters in the isual #yellow)green$, iolet, and ultraiolet regions. What is the

name of the techni"ue being used by this astronomer%

&$ pectroscopy '$ Geometry ($ 7nterferometry *$ :hotometry&ns *

ection 11)2

8<.& red filter passes light at the long waelength end of the isible spectrum as shown, forexample, in Big. 11)2, (omins and Kaufmann, Discovering the Universe, 9th ;dition.

tar 1 and tar are iewed through identical red filters, and tar 1 appears brighter

through the filter than tar . What can be determined from this information%&$ tar 1 is hotter than tar .

'$ tar is hotter than tar 1.

($ tar 1 is more luminous than tar .*$ =othing can be concluded from this fact alone.

&ns *

ection 11)2

<0.When obsered through a set of photometric filters, the brightness of a distant star is seen

to be brightest through the ultraiolet filter, less bright through the blue filter, and faintest

through the yellow filter. What conclusion can be drawn from this information, assumingno absorption of light between the star and the ;arth%

&$ 4here is insufficient information to draw a conclusion about a star>s surface

temperature.'$ 4he star has an intermediate temperature close to that of the un.

($ 4he star has a ery high surface temperature.

*$ 4he star has a ery low surface temperature.

&ns (

Page 16




ection 11)2

<1.+ptical glass filters are used to select certain portions of a star>s light for photometry.Which of the following filters would most closely match the sensitiity of our eyes,

which hae a peak sensitiity at about //0 nm waelength% #ee Big. 3)1 of (omins and

Kaufmann, Discovering the Universe, 9th ;d.$&$ Altraiolet '$ @ed ($ Pellow *$ 'lue

&ns (

ection 11)2 and Bigure 3)1

<.4he difference in the brightness of a star as seen through two different colored filters, for

example, blue and yellow, is directly related to which stellar property%

&$ *istance from the ;arth '$ Duminosity ($ urface temperature *$ @adius&ns (

ection 11)2

<3.& particular star is brighter as seen through a blue filter than through a yellow filter.Which of the following surface temperatures is possible for this star% #ee Big. 11)2,

(omins and Kaufmann, Discovering the Universe, 9th ;d.$&$ 3000 K '$ 1,000 K ($ 2/00 K *$ 000 K

&ns '

ection 11)2

<2.& particular star is fainter as seen through a blue filter than through a yellow filter. Which

of the following surface temperatures is possible for this star% #ee Big. 11)2, (omins and

Kaufmann, Discovering the Universe, 9th ;d.$&$ 1,/00 K '$ 38,000 K ($ 8800 K *$ 3800 K

&ns *

ection 11)2

</.& particular star is approximately e"ually bright when iewed through a blue filter and

through a yellow filter. What is the approximate surface temperature of this star% #eeBig. 11)2, (omins and Kaufmann, Discovering the Universe, 9th ;d.$

&$ 000 K

'$ 1,000 K

($ 3000 K *$ 7t is not possible for a star to be e"ually bright at two different waelengths.

&ns &

ection 11)2

<.4he star @igel, in the constellation +rion, appears brighter through a blue filter than it

does through a yellow filter. uppose that a second star is found that has the same brightness as @igel through the yellow filter, but is brighter than @igel through the blue

filter. Brom this information, we can say conclusiely that the second star has

&$ the same temperature but a lower luminosity.

'$ a higher temperature.

Page 17




($ a lower temperature.

*$ the same temperature but a higher luminosity.

&ns 'ection 11)2

<9.4he star @egulus, in the constellation Deo, appears brighter through a blue filter than itdoes through a yellow filter. uppose that a second star is found that has the same

brightness as @egulus through the blue filter, but is brighter than @egulus through the

yellow filter. Brom this information, we can say conclusiely that the second star has&$ a higher temperature.

'$ the same temperature but a higher luminosity.

($ the same temperature but a lower luminosity.

*$ a lower temperature.&ns *

ection 11)2

<8.4he !enry *raper (atalog of stellar classifications was deeloped beginning in the latenineteenth century. 7t originally classified stars according to the strengths of their

hydrogen lines. 'y the 1<0s, howeer, the se"uence had been reorgani6ed so that thestars were classified by surface temperature. What important scientific deelopment

made possible this reinterpretation%

&$ 4he discoery of nuclear physics and how stars generate their energy'$ 4he discoery of blackbody radiation and the blackbody cure

($ 4he deelopment of atomic physics and how atoms emit light

*$ 4he deelopment of radio astronomy and the detection of molecules in space

&ns (ection 11)/

<<.7n order for 'almer series lines to show up strongly in absorption in stellar spectra,significant numbers of hydrogen atoms hae to hae electrons in the n energy leel.

What then does the appearance of such lines in a stellar spectrum tell us about the

temperature of the star>s surface%&$ 7t tells us ery little about the temperature because hydrogen gas will show

significant 'almer absorption, whateer the surface temperature.

'$ 7t must be high enough to ioni6e the hydrogen atoms by collision in order that they

can absorb from this leel.($ 7t must be reasonably low so that no atoms will hae electrons excited beyond this

energy leel #e.g., to n 3$.

*$ 7t must be reasonably high to excite the electrons to this leel by collisions, but nothigh enough to ioni6e the atoms.

&ns *

ection 11)/

100.Why is there a limited range of stellar surface temperatures around 10,000 K at which

neutral hydrogen gas will absorb isible light in the 'almer series%

&$ 'ecause there must be electrons at the n 3 energy leel in order for 'almer

Page 18




absorption to occur. 7f the gas is too cold, electrons are only in the n 1 and

leels, while if the gas is too hot, the gas is ioni6ed and no electrons are left in the

hydrogen atoms.'$ 'ecause electrons in hydrogen hae to be at the n energy leel in order to

produce absorption in this series. 7f the gas is too cold, most atoms are in the n 1

state, and if it is too hot, most atoms are ioni6ed.($ 'ecause electrons must be in the ground state n 1 in order to undergo 'almer

absorption. 7f the gas is too cold, electrons cannot be excited from this leel, while

if the gas is too hot, there are no electrons left in the n 1 leel.*$ 'ecause there must be sufficient continuum radiation from the stellar surface in the

isible region to be absorbed by the hydrogen gas.

&ns '

ection 11)/

101.Why are 'almer absorption lines ery weak in the spectra of stars with low surface

temperatures, significantly below 10,000 K, for example%

&$ 'ecause the hydrogen atoms hae to be hot enough to be ioni6ed in order to show'almer absorption

'$ 'ecause there is no emitted continuum radiation at 'almer)line waelengths whenthe gas is so cool, so absorption will not be seen

($ 'ecause atoms need electrons that hae been excited by high)temperature

collisions to the n leel in order to undergo 'almer absorption*$ 'ecause hydrogen atoms hae no electrons in any energy leels at these

temperatures

&ns (

ection 11)/

10.7n order for absorption lines in the :aschen series of hydrogen to be seen in the 7@

spectrum of a star #see ec. 2) of (omins and Kaufmann, Discovering the Universe, 9th;d.$, the temperature of its surface must be high enough to excite electrons by collision to

the

&$ n energy leel. ($ ioni6ation leel.'$ n 2 energy leel. *$ n 3 energy leel.

&ns *

ection 2) and 11)/

103.4he spectrum of an ordinary main)se"uence star is a

&$ continuum of colors, crossed by brighter lines caused by emission from the hot

atoms and molecules on the star>s surface.'$ smooth continuum of color, peaking at a specific waelength whose position is

dependent upon the star>s surface temperature.

($ series of emission lines, mostly from hydrogen, the ma5or constituent of stellarsurfaces, that occasionally oerlap to produce sections of continous color.

*$ continuum of colors crossed by dark absorption lines caused by absorption by

cooler atoms and molecules at the star>s surface.

&ns *

Page 19




ection 11)/

102.4he chemical makeup of the un>s surface can be determined&$ by taking a sample of the star>s surface with a space probe.

'$ by examining the chemicals present in a meteorite because it is part of the solar

system.($ by measuring the components of the solar wind with ;arth)orbiting spacecraft.

*$ by solar spectroscopy.

&ns *ection 11)/

10/.4he reason why a doubly ioni6ed helium gas, !e 777, will not produce absorption lines in

a stellar spectrum is&$ that a doubly ioni6ed helium atom is simply a helium nucleus stripped of all its

electrons, so it cannot absorb isible photons.

'$ that the gas temperature on any star is always so high that electrons are excited

beyond energy leels in these atoms from which isible photons can be absorbed.($ that doubly ioni6ed helium is meaningless because neutral helium only contains

one electron.*$ that the gas temperature on star surfaces can neer be hot enough to excite

electrons in this atom to leels from which they will absorb isible photons.

&ns &ection 11)/

10.pectral classification of stars into the lettered categories, +, ', &, B, G, K, and M is

carried out by&$ finding the waelength of peak emission in the continuum spectrum of the star.

'$ determining the relatie masses of the stars by the study of binary star motions, in

order to place them into their proper mass classification.($ determining the total energy emitted at all waelengths by stars, taking account of

the full spread of waelengths and their distances, in order to place the star into its

luminosity class.*$ examining the relatie depths of absorption lines from arious neutral and ioni6ed

atoms in a stellar spectrum.

&ns *

ection 11)

109.4he surface temperature of a nearby star can be determined most precisely by measuring

what parameters%&$ 4he star>s position on the !@ diagram

'$ 4he *oppler shift of the star>s spectral lines

($ 4he relatie strengths of emission lines from different atoms and ions in the star>sspectrum

*$ 4he relatie strengths of absorption lines from different atoms #e.g., !, (a$ and

molecules #e.g., 4i+$ in the star>s spectrum

&ns *

Page 20




ection 11)

108.pectral types of stars #e.g., +, ', &, B, G, K, and M$ define uni"uely their &$ si6es or radii. ($ luminosities.

'$ absolute magnitudes. *$ surface temperatures.

&ns *ection 11)

10<.4he surface temperature of a nearby star can best be determined from spectralclassification by examining

&$ the pattern of spectral absorption lines from arious atoms.

'$ the relatie intensities of light measured through different photometric filters.

($ the peak waelength of the star>s continuum blackbody spectrum.*$ the pattern of emission lines that are on the star>s spectrum.

&ns &

ection 11)

110.Which of the following se"uences of stellar spectral classifications is in correct order of

increasing temperature%&$ K, M, G, B, &, ', + ($ M, K, G, B, &, ', +

'$ &, ', B, G, K, M, + *$ +, ', &, B, G, K, M

&ns (ection 11)

111.4he se"uence of letters that is used to classify star surface temperatures, as determined by

relatie spectral absorption line strengths, in order of decreasing temperature, is&$ &, ', B, G, K, M, +. ($ +, B, M, G, &, ', K.

'$ M, +, B, K, G, &, '. *$ +, ', &, B, G, K, M.

&ns *ection 11)

11.4he un>s classification in terms of its surface temperature, as determined fromabsorption lines in its spectrum, is

&$ M<. '$ G. ($ +1. *$ '.

&ns '

ection 11)

113.Which of the following letters representing spectral classification signifies the hottest

stellar surface temperature%&$ G '$ & ($ K *$ '

&ns *

ection 11)

112.Which of the following four spectral classifications represents the coolest stellar surface

temperature%

&$ ' '$ K ($ G *$ &

Page 21




&ns '

ection 11)

11/.4he spectral class of the star ;nif is K, while that of the un is G. Which of the

following conclusions can be drawn about ;nif from this information%

&$ 7t is intrinsically fainter than the un. ($ 7t is cooler than the un.'$ 7t is intrinsically brighter than the un.*$ 7t is hotter than the un.

&ns (

ection 11)

11.&bsorption line strengths are used in the spectral classification of stars and the

determination of surface temperatures. Which of the following atomic or molecular

constituents will exhibit strong absorption lines in spectra from stars with ery highsurface temperature%

&$ ! '$ (a 77 ($ !e 77 *$ 4i+

&ns (

ection 11) and 4able 11)1

119.7f the surface temperature of a star is ery low, which of the following atomic ormolecular constituents will produce the most prominent absorption lines in its spectrum%

&$ Be 77 '$ 4i+ ($ Mg 77 *$ !e 77

&ns 'ection 11) and 4able 11)1

118.Which of the following molecules produces the strong absorption bands in the spectrum

of a cool M)type star, as can be seen in Big. 11)/ of (omins and Kaufmann, Discoveringthe Universe, 9th ;d.%

&$ !(l, hydrogen chloride ($ !+, water apor

'$ (a7, calcium iodide *$ 4i+, titanium oxide&ns *


11<.4he symbol !e 77 refers to a

&$ helium atom that has lost two electrons.

'$ neutral helium atom #atomic number $ that has lost no electrons.

($ helium molecule that contains two helium atoms.*$ helium atom that has lost one electron.

&ns *

ection 2)/ and 11)

10.Be Q77 is an ioni6ed iron atom with

&$ 13 electrons remoed. ($ 11 electrons remoed.'$ 1 electron remoed. *$ 1 electrons remoed.

&ns (

ection 2)/ and 11)

Page 22




11.!ow many electrons are missing from the ioni6ed silicon atom i 7C%

&$ 4hree '$ +ne ($ Bour *$ Bie

&ns &ection 2)/ and 11)

1.Which of the following atoms or ions will produce the strongest absorption lines in thespectra of stars with the highest surface temperatures%

&$ !e 77, ioni6ed helium ($ (a 77, singly ioni6ed calcium

'$ Be 7, neutral iron *$ ! 7, neutral hydrogen&ns &


13.Which of the following atoms or ions will produce strong absorption lines in the spectraof stars with the reatiely cool surface temperatures%

&$ 4i+, molecules of titanium oxide ($ (a 77, ioni6ed calcium

'$ Mg 77, ioni6ed magnesium *$ !e 7, neutral helium

&ns &ection 11) and 4able 11)1

12.4he spectrum of a star shows the following absorption line characteristics Cery strong

!, weaker Mg 77 and i 77, and no !e 7 or (a 77 lines.H (lassify the spectrum of this star,

using the absorption line strengths in the spectra of stars as shown in Big. 11)/ and 4able11)1 of (omins and Kaufmann, Discovering the Universe, 9th ;d.

&$ ' '$ G ($ K *$ &

&ns *


1/.Ase the absorption line strengths shown in Big. 11)/ and 4able 11)1 of (omins and

Kaufmann, Discovering the Universe, 9th ;d., to determine the spectral class of a starwith the following absorption lines in its spectrum ! lines moderately strongL !e 7 lines

presentL no (a 77, Be 77, or !e 77 lines.H

&$ M '$ ' ($ B *$ &&ns '


1.What will be the spectral class of a star whose spectrum shows the following absorptionlines Cery strong (a 77 linesL weak Be 7 and (a 7 linesL no !e 7, !e 77, or 4i+ linesH%

# Hint: Ase the absorption line strengths shown in Big. 11)/ and 4able 11)1 of (omins and

Kaufmann, Discovering the Universe, 9th ;d.$&$ B '$ + ($ & *$ K

&ns *


19.4he spectrum of a ery distant star shows spectral absorption lines of ioni6ed helium, !e

77, &=* molecular absorption bands from titanium oxide, 4i+. What would be your

conclusion about this star%

Page 23




&$ 7t is probably the spectrum of a binary system, two stars close together, a hot star

and a cooler companion, unresoled as separate stars from our distance, but

contributing separate spectra.'$ 4here must be a ery hot atmosphere containing helium gas oerlaying a much

cooler stellar surface.

($ 4he star must hae a thick, cool atmosphere oerlaying a hot stellar atmosphere.*$ 4here must be cool, interstellar gas containing 4i+ between the star and the ;arth.

&ns &

ection 11)

18.Brom its position in the !ert6sprung)@ussell diagram in Big. 11)9 of (omins and

Kaufmann, Discovering the Universe, 9th ;d., what can you conclude about the star Mira

compared to the un%&$ Mira is cooler and redder but intrinsically brighter than the un.

'$ Mira is cooler, redder, and intrinsically fainter than the un.

($ Mira is hotter than the un and intrinsically brighter.

*$ Mira is hotter and bluer but intrinsically fainter than the un.&ns &

ection 11)9

1<.4he !ert6sprung)@ussell diagram is a plot of

&$ apparent brightness against intrinsic brightness of a group of stars.'$ apparent brightness against distance for stars near the un.

($ luminosity against mass of a group of stars.

*$ absolute magnitude #or intrinsic brightness$ against temperature of a group of stars.

&ns *ection 11)9

130.7f you compare two stars,&$ the one with the larger radius must hae the greater luminosity.

'$ the one with the higher surface temperature must hae the greater luminosity.

($ the one with the smaller absolute magnitude must hae the greater luminosity.*$ the one with the larger surface area has the greater energy flux from its surface.

&ns (

ection 11)9

131.What are the two physical parameters of stars that are plotted in the !ert6sprung)@ussell

diagram%

&$ Mass and surface temperature ($ @adius and mass'$ Duminosity and mass *$ Duminosity and surface temperature

&ns *

ection 11)9

13.Which two physical parameters of stars are plotted on the !ert6sprung)@ussell diagram

to show the systematics of a group of stars #e.g., a cluster$%

&$ Mass and apparent magnitude ($ Duminosity and surface temperature

Page 24




'$ Duminosity and radius *$ urface temperature and mass

&ns (

ection 11)9

133.7n the !ert6sprung)@ussell diagram in Big. 11)9 of (omins and Kaufmann, Discovering

the Universe, 9th ;d., which of the following is the correct se"uence of stars in order ofincreasing intrinsic brightness%

&$ *eneb, the un, irius ', :rocyon ' ($ 4he un, :rocyon ', *eneb, irius '

'$ irius ', *eneb, :rocyon ', the un *$ :rocyon ', irius ', the un, *eneb&ns *

ection 11)9

132.7n the !ert6sprung)@ussell diagram in Big. 11)9 of (omins and Kaufmann, Discoveringthe Universe, 9th ;d., which of the following is the correct se"uence of stars in order of

increasing temperature%

&$ irius ', *eneb, :rocyon ', the un ($ 4he un, :rocyon ', *eneb, irius '

'$ *eneb, the un, irius ', :rocyon ' *$ :rocyon ', irius ', the un, *eneb&ns (

ection 11)9

13/.Asing Bigs. 11)9 and 11)8, determine which of the following is the correct se"uence of

stars in order of increasing si6e or stellar radius%&$ irius ', the un, 'etelgeuse, Mira ($ 'etelgeuse, Mira, the un, irius '

'$ Mira, 'etelguese, the un, irius ' *$ irius ', the un, Mira, 'etelgeuse

&ns *

ection 11)9

13.& star in the lower left part of the !ert6sprung)@ussell diagram, compared to a star in the

middle of the diagram, is&$ larger. '$ cooler. ($ smaller. *$ brighter.

&ns (

ection 11)9

139.(ompared to a star in the middle of the !ert6sprung)@ussell diagram, a star in the upper

right part of the diagram is

&$ fainter.'$ hotter.

($ larger.

*$ nonexistent because there are no stars that appear in the upper right part of thediagram.

&ns (

ection 11)9

138.Where on the !ert6sprung)@ussell diagram do most local stars in our unierse

congregate%

&$ 7n the white dwarf area, the graeyardH of stars

Page 25




'$ 7n the supergiant area, where the most massie stars spend a significant time

($ 7n the giants area, where most stars spend the longest time of their lies

*$ +n the main se"uence, where stars are generating energy by fusion reactions&ns *

ection 11)9

13<.What fraction of the stars surrounding the un are main)se"uence stars%

&$ &lmost all of them, about <0R

'$ 4here are no main)se"uence stars close to the un($ @oughly half of them, about //R

*$ Cery few of them, about 0R

&ns &

ection 11)9

120.What is a dwarf star%

&$ & main)se"uence star

'$ & large, planetary ob5ect, such as Oupiter ($ & star of about the same si6e #diameter$ as the ;arth

*$ &ny star that is significantly smaller than a giant or supergiant star &ns &

ection 11)9

121.What is a white dwarf star%

&$ & large, planetary ob5ect, such as Oupiter

'$ & star of about the same si6e #diameter$ as the ;arth

($ &ny star that is significantly smaller than a giant or supergiant star *$ & main)se"uence star with a surface temperature near 1,000 K

&ns '

ection 11)9

12.7f the surface temperatures of white dwarf stars are 2 times that of the un, and energy

output per unit area of a star depends on the 2th power of the temperature by the tefan)'olt6mann relation, why then are white dwarfs intrinsically so faint%

&$ 'ecause they are ery small

'$ 'ecause they hae ery thin atmospheres that do not emit continuum radiation but

only line emissions, like a low)density gas($ 'ecause they are shrouded in ery thick atmospheres

*$ 'ecause they are moing rapidly away from the un and their spectra are

extremely redshifted, hence they appear faint at isible waelengths&ns &

ection 11)9

123.Measurements indicate that a certain star has a ery high intrinsic brightness #100,000

times as bright as our un$ and yet is relatiely cool #3/00 K$. !ow can this be%

&$ 4he star must be "uite small.

'$ 4he star must be ery large.

Page 26




($ 4here must be an error in obseration because no star can hae these properties.

*$ 4he star must be in the upper part of the main se"uence.

&ns 'ection 11)9

122.4he following are parameters of stars that astronomers obtained from theirmeasurements. Which of these conclusions is obiously erroneous, based on the positions

of these alleged stars on the !ert6sprung)@ussell diagram in Big. 11)8 of (omins and

Kaufmann, Discovering the Universe, 9th ;d.% #Ds and @ s are the luminosity and radius of the un, respectiely.$

&$ Duminosity Ds, @adius @ s, 4emperature 000 KL conclusion main)se"uence

star

'$ Duminosity 102 Ds, @adius 100 @ s, 4emperature /000 KL conclusion a redgiant star

($ Duminosity Ds, @adius 1-10 @ s, 4emperature 0,000 KL conclusion a white

dwarf star

*$ Duminosity 1-100 Ds, @adius 1-100 @ s, 4emperature 0,000 KL conclusion awhite dwarf star

&ns (ection 11)9

12/.Asing the !ert6sprung)@ussell diagram #Big. 11)9 of (omins and Kaufmann,

Discovering the Universe, 9th ;d.$, determine which type of star has the following

characteristics urface temperature of 20,000 K and luminosity 100,000 times that of

the un.H

&$ (ool, red, main)se"uence star ($ White dwarf '$ !ot, blue, main)se"uence star *$ @ed giant

&ns '

ection 11)9

12.Asing the !ert6sprung)@ussell diagram #Big. 11)9 of (omins and Kaufmann,

Discovering the Universe, 9th ;d.$, determine which type of star has the followingcharacteristics & star with surface temperature 10,000 K and luminosity 1-100 times

that of the un.H

&$ @ed supergiant '$ Main se"uence ($ White dwarf *$ @ed giant

&ns (ection 11)9

129.& red supergiant star is found to hae a surface temperature of /00 K and a luminosity100,000 times that of the un. Ase the !ert6sprung)@ussell diagram in Big. 11)8 of

(omins and Kaufmann, Discovering the Universe, 9th ;d., to determine its approximate

radius, compared to that of the un.&$ &bout 10 times larger ($ &bout 1000 times larger

'$ &bout 100 times larger *$ &lmost the same

&ns (

ection 11)9

Page 27




128.What will be the intrinsic brightness or luminosity of a white dwarf star with the same

temperature as the un% #ee Big. 11)9, (omins and Kaufmann, Discovering theUniverse, 9th ;d.$

&$ 2 time the un>s luminosity

'$ 'ecause it has the same surface temperature, it will hae the same brightness($ 10 J of the un>s luminosity

*$ 10 J2 of the un>s luminosity

&ns *ection 11)9

12<.& white dwarf star whose temperature is the same as that of the un will hae a radius

that is #see Big. 11)8, (omins and Kaufmann, Discovering the Universe, 9th ;d.$&$ 10 times smaller than that of the un.

'$ the same si6e as the un because the white dwarf has the same temperature.

($ times smaller than that of the un.

*$ 100 times smaller than that of the un.&ns *

ection 11)9

1/0.'y what standard techni"ue do astronomers find the luminosity class #7, 77, 777, 7C, or C$

of a star%&$ 'y combining the apparent magnitude with the measured distance to the star

'$ 'y obsering the diameter of the star on a photographic plate or ((* image

($ 'y timing how long it takes for the star to be eclipsed by a companion in an

eclipsing binary star system*$ 'y studying the absorption lines in the star>s spectrum

&ns *

ection 11)8

1/1.What is the physical reason why astronomers can find the luminosity class #7, 77, 777, 7C,

or C$ of a star using the star>s spectrum%&$ 4he waelength of maximum emission #gien by Wien>s law$ is affected by the si6e

of the star.

'$ 4he relatie amounts of hydrogen, helium, and other elements are different for stars

of different luminosity classes.($ 4he absorption lines in the spectrum are affected by the density and pressure of the

star>s atmosphere.

*$ 4he absorption lines in the spectrum are affected by the star>s surface temperature.&ns (

ection 11)8

1/.4he luminosity class of a star #7, 77, 777, 7C, or C$ is most closely related to which physical

characteristic of the star%

&$ urface temperature

'$ @adius

Page 28




($ @adial elocity

*$ (hemical composition #amount of hydrogen, helium, etc.$

&ns 'ection 11)8

1/3.& star with a surface temperature of /000 K and a luminosity of greater than 102

timesthat of the un is a member of which luminosity class% #ee Big. 11)<, (omins and

Kaufmann, Discovering the Universe, 9th ;d.$

&$ 77, bright giant '$ C, main se"uence ($ 777, giant *$ 7, supergiant&ns *

ection 11)8 and Bigure 11)<

1/2.&ll of the following statements comparing the un to the giant stars are true except one.Which one is not true% #@efer to Bigure 11)<, (omins and Kaufmann, Discovering the

Universe, 9th ;dition.$

&$ 4he giant stars are more luminous than the un.

'$ 4he giant stars are larger than the un.($ 4he giant stars are hotter than the un.

*$ 4he giant stars hae smaller absolute magnitudes than the un.&ns &

ection 11)8

1//.White dwarfs are not included in the luminosity classification because

&$ they hae not yet begun nuclear reactions and are not yet actie stars.

'$ they are no longer producing energy by nuclear reactions.

($ they are no longer radiating energy away.*$ they are too small.

&ns '

ection 11)8

1/.& star with a surface temperature of 2000 K and a luminosity of about 10 J times that of

the un is a member of which luminosity class% #ee Big. 11)<, (omins and Kaufmann, Discovering the Universe, 9th ;d.$

&$ 777, giant '$ 7, supergiant ($ 77, bright giant *$ C, main)se"uence

&ns *

ection 11)8

1/9.4he star !adar is classified as '1 77, which means that it is

&$ a cool supergiant. ($ a cool giant.'$ a hot, bright giant. *$ a hot supergiant.

&ns '

ection 11)9 and 11)8

1/8.4he star &rcturus is classified as K 777, which means that it is

&$ a hot giant. ($ a cool giant.

'$ a cool supergiant. *$ a cool main)se"uence star.

Page 29




&ns (


1/<.4he star pica is classified as '1 C, which means that it is

&$ a hot main)se"uence star. ($ a hot supergiant.

'$ a cool giant. *$ a cool main)se"uence star.&ns &


10.'arnard>s star, one of our near neighbors, is classified as M/ C. 4his means that it is

&$ a cool main)se"uence star, a red dwarf.

'$ a hot main)se"uence star.

($ a cool giant.*$ a cool supergiant, a huge star.

&ns &


11.Which of the following spectral)luminosity classes corresponds to a red supergiant%

&$ M 7 '$ '9 7 ($ M3 C *$ G 777&ns &


1.4wo stars hae the same luminosity #or absolute magnitude$. +ne star is spectral class B

and the other is spectral class K. Brom this information, we know that

&$ the K)type star is larger than the ')type star.

'$ the ')type star is larger than the K)type star.($ the ')type star is hotter but can be larger, smaller, or the same si6e as the K)type

star.

*$ the K)type star is hotter but can be larger, smaller, or the same si6e as the ')typestar.

&ns &


13.4he star ;lnath is classified as '9 777 while the star &l =a>ir is classified as '9 7C.

(ompared to &l =a>ir, ;lnath has

&$ about the same surface temperature but is intrinsically much fainter.'$ about the same intrinsic brightness but is considerably cooler.

($ about the same surface temperature but is intrinsically much brighter.

*$ about the same intrinsic brightness but is considerably hotter.&ns (


12.4he spectral)luminosity class of the star &rae is ' C, and that of π !erculi is K3 77.

Asing +=DP this information, and without referring to tables or diagrams, we can tell

&$ that α &rae is hotter but intrinsically fainter than π !erculi.

'$ only that α &rae is hotter than π !erculi.

Page 30




($ that α &rae is cooler and intrinsically fainter than π !erculi.

*$ only that α &rae is cooler than π !erculi.

&ns '


1/.4he spectral)luminosity class of the star pica is '1 C, and that of the star τ (eti is G8 C.Brom this, we know that

&$ (eti is cooler but has the same luminosity as pica.

'$ (eti is cooler and has a lower luminosity than pica.

($ (eti is hotter but has the same luminosity as pica.*$ (eti is hotter and has a lower luminosity than pica.

&ns '


1.4he star ζ (anis Ma5oris has an absolute magnitude of J.2 and a spectral class of '.

Asing Bigures 11)9 and 11)8 of (omins and Kaufmann, Discovering the Universe, 9th

;d., how would (anis Ma5oris be classified%&$ ')type white dwarf '$ ' 777 ($ ' C *$ ' 7&ns (


19.& particular star has an absolute magnitude of 0 and a spectral class similar to that of the

un. Asing Bigure 11)< of (omins and Kaufmann, Discovering the Universe, 9th ;d.,

how would this star be classified%&$ G C '$ G)type white dwarf ($ G 7 *$ G 777

&ns *


18.& particular star has an absolute magnitude of I1 and a spectral class of &/. Asing

Bigures 11)9 and 11)< of (omins and Kaufmann, Discovering the Universe, 9th ;d., how

would this star be classified%&$ &/ 7 '$ &)type white dwarf ($ &/ C *$ &/ 777

&ns '


1<.4he star ζ (anis Ma5oris has an absolute magnitude of J.2 and a spectral)luminosity

class of ' C. 4he star γ (rucis has a spectral class of M2 and the same absolute

magnitude as (anis Ma5oris. Asing Bigure 11)< of (omins and Kaufmann, Discovering

the Universe, 9th ;d., the spectral)luminosity class of (rucis is probably&$ M)type white dwarf. '$ M2 77. ($ M2 7a. *$ M2 C.

&ns '


190.What is spectroscopic parallax%

&$ 4he apparent change in position of the absorption lines in a star>s spectrum due tothe *oppler shift caused by the ;arth>s motion around the un

Page 31




'$ 4he apparent change in position of a nearby star compared to distant background

stars due to the motion of the ;arth around the un

($ 4he change in position of the absorption lines in a star>s spectrum due to the*oppler shift caused by the star>s motion around the center of mass in a binary star

system

*$ 4he distance to a star measured using the spectral)luminosity class of the star andthe inerse s"uare law

&ns *

ection 11)<

191.Which of the following possible factors most seriously limits the accuracy of

spectroscopic parallax%

&$ tars of the same spectral)luminosity class can hae a range of temperatures.'$ 7t is difficult to measure angular displacement accurately for distant stars.

($ tars of the same spectral)luminosity class can hae a range of absolute

magnitudes.

*$ 7t is not possible to classify the spectral)luminosity class of een a nearby staraccurately.

&ns (ection 11)<

19.4wo stars, one classified &2 C and the other &2 777, hae the same apparent magnitude.4here is no significant amount of absorption of starlight by interstellar material. Brom

this information we know that

&$ the &2 C star is cooler than the &2 777 star.

'$ the &2 C star is closer to the un than the &2 777 star.($ the &2 C star is farther from the un than the &2 777 star.

*$ the &2 C star is hotter than the &2 777 star.

&ns 'ection 11)<

193.4wo stars, one classified &2 C and the other B8 C, hae the same apparent magnitude.4here is no significant amount of absorption of starlight by interstellar material. Brom

this information we know that

&$ the &2 C star is farther from the un than the B8 C star.

'$ both stars are at the same distance from the un.($ the &2 C star is smaller than the B8 C star.

*$ the &2 C star is closer to the un than the B8 C star.

&ns &ection 11)<

192.When two stars of une"ual mass orbit each other under their mutual graitationalattraction, where is the center of mass of the system located%

&$ &t a point halfway between the centers of the stars

'$ &t a point between the stars, closer to the less massie star

($ &t the center of the more massie star

Page 32




*$ &t a point between the two stars, closer to the more massie star

&ns *

ection 11)< and Bigure 11)11

19/.What proportion of isible stars in our nighttime sky are members of multiple)star

systems, such as binary stars%&$ Dess than 1R ($ +nly about S, or /R

'$ -3, or almost 90R *$ (lose to 100R

&ns 'ection 11)10

19.Which one of the following statements is correct for an isolated star #i.e., a star that is not

in a binary star system$%&$ 4here are seeral ways to measure its mass accurately.

'$ 7ts mass can be measured accurately only if its luminosity and temperature can be

measured.

($ 7ts mass can be measured accurately only if its distance can be found.*$ 7t is not possible to measure the star>s mass accurately.

&ns *ection 11)10

199.What is the only way to measure the mass of a star accurately%&$ Measure its distance using trigonometric parallax and its brightness using

photometry

'$ 7t is not possible to measure the mass of a star.

($ Measure its spectral type and luminosity class, then use the !)@ diagram*$ Measure its graitational effect on another ob5ect

&ns *

ection 11)10

198.!ow do astronomers measure the masses of stars%

&$ 'y obsering the star>s brightness at different waelengths #colors$'$ 'y obsering the motion of two stars in a binary star system

($ 'y measuring the star>s brightness, temperature, and distance

*$ 'y measuring the star>s brightness, and obtaining its radius using the !)@ diagram

&ns 'ection 11)10

19<.Which important stellar parameter can be deried from the study of binary stars mutually bound to each other by graitational forces%

&$ tellar masses

'$ 4he distance of the stars from the ;arth($ 4he age of the stars

*$ urface temperatures of the stars

&ns &

ection 11)10

Page 33




180.Which important property of stars can be best determined by obserations of binary stars

systems%&$ tellar mass ($ *istance from the ;arth

'$ urface temperature *$ :ulsation period

&ns &ection 11)10

181.+ne important aspect of the study of binary star systems, as distinct from single stars, isthat it proides

&$ a measurement of the masses of stars.

'$ a measurement of the surface temperatures of stars.

($ a erification of the *oppler e"uation for waelength shift of light from moingob5ects.

*$ a measurement of the composition #abundances of elements$ inside stars.

&ns &

ection 11)10

18.!ow do two une"ual)mass stars moe around each other, in general, in a binary starsystem%

&$ 7n a single circular orbit around the same center, and always on opposite sides from

each other '$ 7n straight lines, back and forth past each other

($ 4he low)mass star moes in a circular orbit around the high)mass star, which

remains stationary

*$ 7n elliptical orbits, about a common center of massH&ns *

ection 11)10

183.4o determine the sum of the masses of a isual binary star system, we need to measure

&$ the temperatures and periods of the stars.

'$ the distance from us and the semima5or axis of the orbit of one star relatie to theother.

($ the period and the semi)ma5or axis.

*$ the temperatures and the distance from us.

&ns (ection 11)10

182.What is the difference between an optical double star and a isual binary star%&$ &n optical double is an illusionTthe stars are at ast distances from each other and

are not actually orbiting each otherTwhereas in a isual binary, the stars are

actually orbiting each other.'$ 4here is no differenceTthey are two names for the same thing.

($ 4he stars in an optical double star are actually orbiting each other, whereas a isual

binary is an illusionTthe stars are at ast distances from each other and are not

actually orbiting each other.

Page 34




*$ +ptical double stars can be seen as separate stars only through a telescope, whereas

isual binaries can be seen with the unaided eye #e.g., the star Mi6ar in the 'ig

*ipper>s handle$.&ns &

ection 11)10

18/.7n order for a pair of stars to be classified as an optical double, which one of the

following conditions must be true%

&$ 4he stars must lie in almost the same direction from the ;arth but must not beorbiting around each other.

'$ 4he stars must be orbiting around each other, and one must periodically cross in

front of the other #i.e., it must eclipse the other$ as seen from the ;arth.

($ 4he stars must be orbiting around each other, and absorption or emission lines from both stars must be isible in the spectrum.

*$ 4he stars must be orbiting around each other, and both stars must be isible through

telescopes from the ;arth.

&ns &ection 11)10

18.7n order for a pair of stars to be classified as a isual binary, which one of the following

conditions must be true%

&$ 4he stars must be orbiting around each other, and both stars must be isible throughtelescopes from the ;arth.

'$ 4he stars must be orbiting around each other, and absorption or emission lines from

both stars must be isible in the spectrum.

($ 4he stars must be orbiting around each other, and one must periodically cross infront of the other #i.e., it must eclipse the other$ as seen from the ;arth.

*$ 4he stars must lie in almost the same direction from the ;arth but must not be

orbiting around each other.&ns &

ection 11)10

189.7n a particular binary star system, only one star is isible because the other star is too

faint to see at that distance. &n astronomer measures the si6e #semima5or axis$ and period

of the orbit of the isible star. Brom this information, the astronomer

&$ cannot calculate anything about the massTboth stars hae to be isible to do so.'$ can calculate the mass of each star.

($ can calculate the sum of the masses of the two stars but not the mass of each star

separately.*$ can calculate the mass of the isible star but not that of the unseen star.

&ns (

ection 11)10

188.& particular star in a binary star system orbits the other in an elliptical orbit with a

semima5or axis of 3 &A and a period of / years. What is the sum of the masses of the two

stars in the system%

Page 35




&$ 0.< M.

'$ 1.1 M.

($ 13.< M.

*$ 0.09 M.

&ns '


18<.7f instead of being orbited by Oupiter, the un were orbited by a star of 1.8 solar masses at

Oupiter>s distance of /. &A #or, more precisely, the un and the other star were orbitingeach other /. &A apart$, what would be the orbital period of the system% #Pou mightwant to compare your answer to the actual orbital period of Oupiter, 11.< years.$

&$ 9.1 years '$ <.2 years ($ /0. years *$ 11.3 years

&ns &ection 11)10 and 4oolbox 11)2

1<0.4wo stars in a binary system orbit around a common point that is&$ always exactly midway between the two stars.

'$ closer to the less massie star.

($ closer to the more massie star.

*$ always inside one of the stars.&ns (

ection 11)10 and Bigure 11)11

1<1.4he relationship between mass and luminosity of stars on the main se"uence is that

&$ the luminosity of stars increases with mass up to a peak around one solar mass,

then decreases as the mass continues to increase.'$ luminosity is independent of the stellar mass.

($ the larger the stellar mass, the larger the luminosity.

*$ the greater the stellar mass, the less the luminosity.&ns (

ection 11)11

1<.Where are the most massie stars to be found in the main se"uence of a !ert6sprung)@ussell diagram%

&$ 4he upper left end

'$ Main)se"uence stars all hae approximately the same mass, by definition.($ 7n the center

*$ 4he lower right end

&ns &ection 11)11

1<3.What will be the mass of a main)se"uence star that has a luminosity 1000 times greater

than that of the un% #ee Big. 11)1, (omins and Kaufmann, Discovering the Universe,9th ;d.$

&$ 10/ solar masses ($ 0.1 solar mass

'$ / solar masses *$ 1000 solar masses&ns '

ection 11)11

Page 36




1<2.&ccording to the mass)luminosity relation shown in Big. 11)1 of (omins and

Kaufmann, Discovering the Universe, 9th ;d., what is the mass of the star @egulus #α

Deonis, the brightest star in the constellation Deo$% ee also the !ert6sprung)@usselldiagram Bigure 11)9.

&$ 'etween ./ and / solar masses ($ 'etween 10 and 1/ solar masses

'$ 'etween 1./ and solar masses *$ 'etween 8 and 10 solar masses&ns &

ection 11)11

1</.Asing the !ert6sprung)@ussell diagram and the mass)luminosity relationship for main)

se"uence stars #Big. 11)1 of (omins and Kaufmann, Discovering the Universe, 9th ;d.$,

determine which of the following type of main)se"uence stars will hae the highest

mass%&$ M '$ & ($ + *$ G

&ns (

ection 11)11

1<.Asing the !ert6sprung)@ussell diagram in Big. 11)9 of (omins and Kaufmann,

Discovering the Universe, 9th ;d., and the mass)luminosity relationship for main)se"uence stars shown in Big. 11)1, which of the following is the correct se"uence of

stars in increasing order of mass%

&$ @egulus, 'arnard>s tar, the un, &ltair '$ 'arnard>s tar, &ltair, the un, @egulus

($ 'arnard>s tar, the un, &ltair, @egulus

*$ @egulus, &ltair, the un, 'arnard>s tar

&ns (ection 11)11

1<9.Ase the !ert6sprung)@ussell diagram #Big. 11)9$ and the mass)luminosity relation #Big.11)1$ in (omins and Kaufmann, Discovering the Universe, 9th ;d., to estimate the mass

of Cega, which is an &+ C main)se"uence star with a surface temperature of about

10,000 K.&$ 'etween 1./ and /.0 solar masses ($ less than 1.0 solar masse

'$ &bout 10 solar masses *$ 'etween /.0 and 10.0 solar masses

&ns &

ection 11)11

1<8.4he radial)elocity cure of a star in a binary star system is a plot against time of

&$ the speed of the star in a direction perpendicular to the line of sight to the star.'$ the position of the star in celestial coordinates.

($ the ariation of *oppler shift of its spectral lines and hence of its speed toward or

away from us.*$ the temperature of the star as determined from the moement of the peak

waelength of its spectrum.

&ns (

ection 11)1

Page 37




1<<.&bsorption lines in the spectra of some binary stars are seen to change periodically from

single to double lines and back again. Why is this%&$ 4he effect of the graitational field of one star on the atoms of the second star

produces spectral line shifts periodically.

'$ 4he magnetic field of one star produces ?eeman periodic splitting of spectral linesin atoms of the second star.

($ +scillations on the surfaces of the stars leads to *oppler)shifted lines.

*$ Motion toward and away from the ;arth during their orbital motion results in*oppler shift of light from these stars at times and no shift when the stars are

moing perpendicular to the line of sight.

&ns *

ection 11)1

00.&n eclipsing binary system consists of

&$ two stars orbiting each other in which periodic spectral line shifts due to *oppler

shift are measured.'$ two stars that are clearly resoled as separate but orbiting each other and obiously

graitationally bound to each other.($ a star that is periodically eclipsed by the Moon.

*$ two stars whose combined light output toward the ;arth aries regularly as one star

periodically moes in front of the other.&ns *

ection 11)13

01.&n eclipsing binary system consists of &$ a star that is periodically eclipsed by the Moon.

'$ two stars that periodically eclipse each other, as seen from the ;arth.

($ two stars in which spectral lines moe back and forth periodically due to *opplershift, indicating mutually orbiting stars.

*$ two mutually orbiting and graitationally bound stars that are close enough to be

resoled when iewed from the ;arth.&ns '

ection 11)13

0.4he light intensity from a particular star remains essentially constant except for short andregular decreases and increases by a fixed amount. What is the explanation for this

phenomenon%

&$ +ne star is regularly eclipsing its companion as they moe in mutual orbits whose plane is close to the line of sight.

'$ & ariable star is pulsating in si6e, temperature, and intensity.

($ & massie, dark planet is periodically passing in front of the star>s isible surface.*$ hells of absorbing gas and dust are being periodically e5ected from the star>s

surface and are subse"uently dispersing into space.

&ns &

ection 11)13

Page 38




03.Which of the following obserations would =+4 be an indication of a binary star

system%&$ 4he starH appears to moe in a straight line against a background field of stars.

'$ & starH appears to become periodically dimmer and then brighter for a few hours

at a time.($ & starH image periodically separates into two distinct images and then blends

again.

*$ 4he starH appears to wiggle in its path across our sky against the background stars.&ns &


02.What condition is necessary in order for us to see eclipses of stars in binary star systems%&$ 4he stars must hae ery similar surface temperatures, whateer the inclination of

their orbital plane to the line of sight, in order for us to see a significant eclipse.

'$ 4he line of sight from the ;arth to the star system must be ery close to the

perpendicular to the orbital plane of the stars.($ 4he line of sight from the ;arth to the star system must be in, or ery close to, the

orbital plane of the stars.*$ +ne of the stars must be much bigger than the other so that it can hide its smaller

companion when the orbital plane is at a large angle to the line of sight.

&ns ((lassification (

ection 11)13

0/.Which of the following ma5or perturbations can occur to a close binary system andradically alter the eolution and behaior of the two indiidual stars%

&$ 4he graitational disturbance of one star>s motion by its companion to force it to

moe in an orbit'$ 4he transfer of matter from one star to its companion

($ 4he heating of the locali6ed areas of the atmosphere of one star by its companion

*$ 4he eclipsing of the light from one star by the other when iewed from the ;arth&ns '

(lassification (

ection 11)13

0.What particular and ery important phenomenon fre"uently occurs in binary star systems

where the stars are ery close together%

&$ 4he less massie star, in its elliptical orbit, will repeatedly pass through the thin,extended atmosphere of the second star, producing periodic rises and falls in light

output from the star system.

'$ 4he radiation from the hotter star will slowly heat and eaporate away the coolerstar.

($ Mass lost from one star is deposited on its companion.

*$ 4he less massie star spirals slowly into its more massie companion because of

tidal interactions.

Page 39




&ns (

(lassification (

ection 11)13

09.uppose we obsere the light cure of a totally eclipsing binary like that in Big. 11)1/ in

(omins and Kaufmann, Discovering the Universe, 9th edition. 4he brightness fallsgradually from magnitude / to magnitude < and remains there for 1 hours before

increasing gradually to magnitude /. 4hen, after a while, it drops gradually to magnitude

, remains there for 8 hours, and returns to magnitude /. What conclusion can be drawnfrom this light cure%

&$ 4he star with the higher temperature is the smaller star.

'$ 4he star with the higher temperature is the larger star.

($ 4his system is experiencing tidal distortion.*$ 4he light cure is in error because we cannot hae two minima of different

durations.

&ns *

ection 11)13

08.7n the case where a large number of stars of different masses all form at the same time#e.g., in a cluster of stars$, what does the phrase initial mass functionH mean%

&$ 4he mass of the largest star in the cluster diided by the mass of the smallest star

'$ 4he mass of the original cloud of gas and dust that collapsed to form the cluster ($ & graph or e"uation relating the mass of each star to its luminosity

*$ 4he number of stars that form at each mass

&ns *

ection 11)12

0<.4he process of eolution of stars in our unierse has been interpreted by

&$ matching theoretical models to the properties of similar stars at different distancesfrom the ;arth since we are seeing more distant stars at an earlier time, when the

light left them.

'$ matching theoretical models to the collectie properties, such as luminosity,temperature, and si6e, of millions of stars as we see them.

($ designing theoretical models solely on the basis of the known properties of matter,

without reference to obserational data on real stars, since we do not hae a

sufficiently long time base for stellar obserations.*$ matching theoretical models to the detailed obseration of a few stars as we watch

them change in luminosity, temperature, and si6e during their eolution.

&ns 'ection (hapter 11

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Astronomy - Chapter 11 Test