astronomy - chapter 14 test

8/10/2019 Astronomy - Chapter 14 Test

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CHAPTER 14: Black Holes: Matters of Gravity

1.Each one of these is a consequence of the postulates of special relativity except one.

Which is the exception?

A) The mass of an object moving ith respect to an observer is larger than the massmeasure! by a !ifferent observer ho is at rest ith respect to the object.

") A cloc# moving ith respect to an observer tic#s more sloly than hen measure!

by an observer ho is moving along ith the cloc#.$) The length of an object moving ith respect to an observer is shorter than it is

hen measure! by a !ifferent observer moving along ith the object.

%) The avelength emitte! from a source moving ith respect to an observer ill be!ifferent from the avelength measure! by an observer ho is moving along ith

the source.

Ans& %

'ection& 1(1

*.A cloc# is moving across your line of sight ith its face turne! toar! you. Each of the

folloing statements about this cloc#+ as seen by you+ is true except one. Which

statement is incorrect?A) The cloc# ill run slo compare! to a cloc# in your han!.

") The cloc# ill appear shorter than it oul! if it ere at rest.$) The cloc# ill appear thinner+ front to bac#+ than it oul! if it ere at rest.

%) The cloc# ill appear more !ense than it oul! if it ere at rest.

Ans& $'ection& 1(1

,.Why !oes Einstein-s theory of special relativity carry the name special/?

A) 0t !eals only ith motion at spee!s significantly less than the spee! of light.") 0t !eals only ith objects that are at rest relative to each other.

$) 0t !eals only ith gravity an! not ith other #in!s of forces.%) 0t !eals only ith objects moving in a straight line at a constant spee!.Ans& %

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(.o must an object be moving for us to be able to use the theory of special relativity to

!escribe the object?

A) 0t must be moving close to the spee! of light2 if this is true+ then ho spee! an!

!irection change is not important.") 0t must be moving at a constant spee! in a straight line2 ho fast it is moving is not

important.

$) 0t must be moving in a constant !irection2 ho spee! changes is unimportant.%) 0t must be moving at a constant spee!2 hether the !irection of motion changes is

unimportant.

Ans& "'ection& 1(1

3.0n hich of the folloing frames of reference/ oul! matter behave exactly as it oul!

in a stationary frame of reference?A) Accelerating !onar! in an elevator hose cable has bro#en

") 4oving upar! against gravity in an elevator as it accelerates from rest

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$) 4oving at a constant velocity

%) 4oving at a constant spee! in a circular path+ such as in an orbit

Ans& $'ection& 1(1

5.Which of the folloing is a correct an! complete statement of Einstein-s first postulate ofspecial relativity?

A) 6our !escription of physical reality is the same regar!less of the constant velocity

at hich you move.") 6our !escription of physical reality is the same regar!less of the !irection in hich

you move+ even if the spee! changes.

$) 6our !escription of physical reality is the same regar!less of ho you move.

%) 6our !escription of physical reality is the same regar!less of the constant spee! athich you move+ even if !irection changes.

Ans& A

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7.'uppose you are in a jet airliner traveling at a constant spee! of (88 #m9h in a constant

!irection. All in!os are bloc#e! so you cannot see outsi!e+ an! there are no vibrationsfrom the engines. What experiment can you !o to !etermine that you are in fact moving?

A) 'uspen! a ball by a threa! from the ceiling an! measure the angle the threa! ma#es

ith the vertical.") :one;all experiments ill give the same results that you oul! get hen at rest

on the groun!.

$) 4easure the spee! of a soun! ave traveling up the aisle


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!irections 8 m. At the same time+ Foanne 8 m because of the motion of the spaceship.

") 188 m because she is at rest/ on the spaceship.$) We cannot tell from the information given.

%) about 118 m because both she an! the spaceship are moving.

Ans& "'ection& 1(1

1,.'uppose you see a spaceship ith a cloc# on it hurtling past you at =8 of the spee! oflight. As it goes by+ the secon! han! on the ship-s cloc# tic#s off five secon!s. o much

time elapse! on your cloc# hile this as happening?

A) 4ore than five secon!s if the spaceship is approaching you an! less than five

secon!s if it is moving aay from you

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") Dess than five secon!s

$) 4ore than five secon!s

%) ive secon!s;the same as on the ship-s cloc# Ans& $

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1(.'uppose you are aboar! a spaceship that is passing the Earth at =8 of the spee! of light.

6ou see a cloc# on the Earth tic# off five secon!s. o much time elapses on your on

cloc# hile this is happening?A) ive secon!s;the same as on the ship-s cloc#

") 4ore than five secon!s

$) 4ore than five secon!s if you are approaching the Earth less than five secon!s if

you are moving aay from the Earth%) Dess than five secon!s

Ans& "

'ection& 1(1

13.A chil! on a playgroun! sing is singing bac# an! forth


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move more sloly than on your ship.

") The moving spaceship appears to be shorter than yours+ an! time on it appears to

move more quic#ly than on your ship.$) The moving spaceship appears to be longer than yours+ an! time on it appears to

move more quic#ly than on your ship.

%) The moving spaceship appears to be longer than yours+ an! time on it appears tomove more sloly than on your ship.

Ans& A

'ection& 1(1

1=.0n a TG tube+ the picture is create! by a beam of electrons that travel !on the tube at a

very high spee!. What is the mass of one of these electrons+ compare! to an electron at

rest?A) The mass of an electron is measure! to be the same regar!less of ho fast it is

moving.

") The moving electron appears to have a smaller mass.

$) The electron appears to have a greater mass if you are in front of the tube


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A) 0t inclu!es gravitation an! accelerate! motion.

") 0t inclu!es the change in the rate of passage of time hen objects are in motion.

$) 0t inclu!es motion at an! above the spee! of light.%) 0t inclu!es only constant+ unaccelerate! motion.

Ans& A

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**.'uppose a satellite ere place! in orbit aroun!


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%) tic# faster the closer it comes to the source of gravity.

Ans& $

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*7.Accor!ing to Einstein-s theory of general relativity+ if you atch a cloc# from a !istant

location as it is move! closer to a source of gravity+ you ill see the cloc#A) maintain the same rate since time is unaffecte! by gravity.

") only change its rate if it is moving rapi!ly but maintain its stan!ar! rate if

stationary in a gravity fiel!.$) slo !on.

%) run faster.

Ans& $

'ection& 1(*

*=.0n an observation of a group of stars a!jacent to the limb of the 'un !uring a total solar

eclipse+ hich ay ill the nearest star to the solar limb appear to move because of the

curvature of space near the 'un?A) Toar! the solar limb

") Aay from the solar limb an! toar! the center of the 'un$) 0n a !irection parallel to the limb of the 'un

%) Dight is unaffecte! by the curvature of space+ an! so the star-s position ithin the

group ill remain unchange!.Ans& "

'ection& 1(,

*>.'uppose you ere far from a planet that ha! a very strong gravitational fiel!+ an! a lightave reaches you from a source of hy!rogen


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A) The 'un exerts a gravitational force on the Earth across empty space.

") The Earth an! the 'un are continually exchanging photons of light in a ay that

hol!s the Earth in orbit.$) 4atter contains quar#s+ an! the Earth an! the 'un attract each other ith the color

force/ beteen their quar#s.

%) 'pace aroun! the 'un is curve!.Ans& A

'ection& 1(,

,*.Accor!ing to general relativity+ hy !oes the Earth orbit the 'un?

A) 4atter contains quar#s+ an! the Earth an! the 'un attract each other ith the color

force/ beteen their quar#s.

") 'pace aroun! the 'un is curve!+ an! the Earth follos a geo!esic in this curve!space.

$) The 'un exerts a gravitational force on the Earth across empty space.

%) The Earth an! the 'un are continually exchanging photons of light in a ay that

hol!s the Earth in orbit.Ans& "

'ection& 1(,

,,.Which of the folloing is not a test of general relativity+ but rather a test of special

relativity?A) The length of a moving object !ecreases hen observe! by a stationary observer.

") The avelength of light increases as it leaves a region of gravitational fiel!.

$) Dight travels in a curve! path in a gravitational fiel!.

%) The perihelion position of 4ercury-s orbit precesses more quic#ly than is pre!icte!by :etonian theory.

Ans& A

'ection& 1(,

,(.'uppose it ere possible to loer a yello so!ium lamp !on toar! the event horiJon

of a blac# hole. What oul! you see hile atching from a safe !istance?A) The brightness or color oul! each remain unchange!.

") The light from the lamp oul! change to orange an! then re!.

$) The light oul! remain yello+ but there oul! be feer an! feer photons being

emitte! from it.%) The light from the lamp oul! change to green an! then blue.

Ans& "

'ection& 1(,

,3.Each of the folloing is an observation confirming the pre!ictions of general relativity+

except one. Which one is the exception?A) Dight is !eflecte! in the curve! space near the 'un.

") The perihelion of the orbit of 4ercury shifts more than the amount pre!icte! by

:etonian physics.

$) Krimor!ial blac# holes have been !etecte!.

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%) The spectra of stars exhibit the gravitational re!shift.

Ans& $

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,5.Dight leaving the surface of a neutron star is strongly re!shifte!. What name is given to

this effect?A) $osmological re!shift $) Leeman effect

") Iravitational re!shift %) %oppler shift

Ans& "'ection& 1(,

,7.Which of the folloing is the loer limit for a mainsequence star that ill eventually

form a blac# hole?A) 38 solar masses $) , solar masses

") *3 solar masses %) 1.( solar masses

Ans& "

'ection& 1((

,=.A blac# hole can be thought of asA) a star ith a temperature of 8 H+ emitting no light.

") the point at the center of every star+ provi!ing the star-s energy by gravitational

collapse.$) !ensely pac#e! matter insi!e a small but finite volume.

%) a region ith such a large mass !ensity that even electromagnetic ra!iation cannot

escape.

Ans& %'ection& 1((

,>.'uppose that a neutron star of *.= solar masses is part of a binary star system in hich theother star is a normal giant star. What oul! happen if half a solar mass of material ere

transferre! onto the neutron star from its companion?

A) The neutron star oul! explo!e as a supernova.") The neutron !egeneracy pressure insi!e the neutron star oul! increase to balance

the increase! gravitational force ithin the neutron star.

$) The increase! gravitational force oul! transform the neutrons into quar#s+ an! the

neutron star oul! reestablish equilibrium as a quar# star of smaller !iameter.%) The neutron star oul! collapse an! become a blac# hole.

Ans& %

'ection& 1((

(8.What is the li#ely final fate of a star hose mass is 13 solar masses hen it is on the main

sequence?A) 0t ill collapse an! become a blac# hole.

") 0t ill con!ense to the point here it is compose! completely of neutrons+ the

!egeneracy of hich ill prevent further shrin#age.

$) The !egeneracy of the electrons ithin the star ill prevent collapse belo the

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!iameter of a hite !arf.

%) 0t ill imme!iately split into to an! become a binary star system.

Ans& "'ection& 1((

(1.What is the li#ely final fate of a star hose mass is ,8 solar masses hen it is on the mainsequence?

A) 0t ill collapse an! become a blac# hole.

") 0t ill con!ense to the point here it is compose! completely of neutrons+ the!egeneracy of hich ill prevent further shrin#age.

$) The !egeneracy of the electrons ithin the star ill prevent collapse belo the

!iameter of a hite !arf.

%) 0t ill imme!iately split into to an! become a binary star system.Ans& A

'ection& 1((

(*.0n a binary star system+ an unseen component is foun! to have a mass of about = solarmasses. 0t oul! be visible if this ere a normal star+ so it must be a collapse! object.

Theoretical consi!erations tell us that it must beA) a blac# hole. ") a neutron star. $) a hite !arf. %) a bron !arf.

Ans& A

'ection& 1((

(,.0n a binary star system+ one component is foun! to have a mass of about , solar masses+

an! the other a mass of about 7 solar masses. The ,solarmass star is visible from the

Earth+ but the 7solarmass star is not. Theoretical consi!erations tell us that the 7solarmass star must be

A) a neutron star. $) a hite !arf.

") a cool planetary object. %) a blac# hole.Ans& %

'ection& 1((

((.0n reference to blac# holes+ a singularity is

A) a place just outsi!e the event horiJon of a rotating blac# hole here it is impossible

to remain at rest.

") an entry point in the event horiJon of a blac# hole through hich material isalloe! to pass unhin!ere!.

$) a place here a nonJero mass occupies Jero volume.

%) a place here the escape velocity exactly equals the spee! of light.Ans& $

'ection& 1((

(3.What is a singularity?

A) A particleantiparticle pair

") A tunnel into another universe

$) Any point at the 'charJschil! ra!ius of a blac# hole

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%) A point of infinite !ensity

Ans& %

'ection& 1((

(5.What is a superstring?

A) A ne #in! of force postulate! to #eep a companion binary star from falling into ablac# hole

") The line of material along hich the jets shoot out from neutron stars an! blac#

holes$) A ne theory of physics that is inten!e! to !escribe hat happens insi!e the event

horiJon of a blac# hole

%) The force that hol!s quar#s together in a quar# star

Ans& $'ection& 1((

(7.What separates a blac# hole from the rest of the universe?

A) 0ts crystalline crust $) 0ts singularity") The surface of the ergoregion %) 0ts event horiJon

Ans& %'ection& 1(3

(=.What is the event horiJon of a blac# hole?A) The surface/ at hich any object passing through it ill leave ith greater energy

than it entere!

") The surface/ at hich all events happen

$) The infinitesimally small volume at the center of the blac# hole that contains all ofthe blac# hole-s mass

%) The surface/ from insi!e of hich nothing can escape

Ans& %'ection& 1(3

(>.At hat location in the space aroun! a blac# hole !oes the escape velocity become equalto the spee! of light?

A) At the point here cloc#s are observe! to slo !on by a factor of *

") @nly at the central singularity

$) At the event horiJon%) At the point here escaping M rays are pro!uce!

Ans& $

'ection& 1(3

38.The escape velocity at the event horiJon aroun! a blac# hole is

A) infinite. $) much less than the spee! of light.") equal to the spee! of light. %) just un!er the spee! of light.

Ans& "

'ection& 1(3

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31.0f you ere to pass inar! through the event horiJon of a blac# hole+

A) there oul! be nothing you coul! !o to prevent yourself from falling !irectly into

the singularity at the center.") you coul! escape again provi!e! that the blac# hole is spinning.

$) you coul!+ ith a poerful roc#et+ move outar! ithin the blac# hole+ thereby

avoi!ing the singularity until your fuel ran out+ but you coul! never escape bac#out through the event horiJon.

%) you coul! avoi! the singularity by going into orbit aroun! it+ but you coul! never

move outar! again from any particular orbit.Ans& A

'ection& 1(3

3*.Where oul! you loo# for an event horiJon?A) 0n the photosphere of a star


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35.The 'charJschil! ra!ius refers to

A) half the !iameter of the singularity in a blac# hole.

") the !istance to hich gas is ejecte! in a planetary nebula.$) half the !iameter of a neutron star.

%) the !istance from the center of a blac# hole to the point at hich the escape

velocity becomes equal to the spee! of light.Ans& %

'ection& 1(3

37.Accor!ing to the equation in Toolbox 1(1 in $omins an! Haufmann+Discovering the

Universe, 7th E!.+ hat is the 'charJschil! ra!ius of a *solarmass blac# hole?

A) 58 #m ") 5888 #m $) 5 m %) 5 #m

Ans& %'ection& 1(3 an! Toolbox 1(1

3=.Accor!ing to the equation in Toolbox 1(1 in $omins an! Haufmann+Discovering the

Universe, 7th E!.+ hat happens to the 'charJschil! ra!ius of a blac# hole if you !oublethe amount of mass in the blac# hole?

A) The 'charJschil! ra!ius is !ouble!.") The 'charJschil! ra!ius is halve!.

$) The 'charJschil! ra!ius !ecreases by a factor of (.

%) The 'charJschil! ra!ius is qua!ruple!


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eight

%) The mass+ the angular momentum+ an! the electric charge

Ans& %'ection& 1(3

5*.The only physical properties that are necessary to !escribe a blac# hole an! its interactionith the rest of the universe completely are

A) its total mass+ the total angular momentum or spin+ an! its temperature.

") its total mass+ the chemical or atomic structure of the matter ithin it+ an! itsoverall siJe.

$) the siJe of the event horiJon+ the strength of its magnetic fiel!+ an! the siJe of its

soli! core.

%) its total mass+ total electric charge+ an! total angular momentum or spin.Ans& %

'ection& 1(3

5,.Which of the folloing can you never #no about a blac# hole?A) The type of material insi!e it

") 0ts angular momentum


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%) The lefthan! one ill be electrically neutral an! the righthan! one ill have an

enormous electric charge.

Ans& %'ection& 1(3

55.'uppose that a large piece


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$) A blac# hole that fills its 'charJschil! ra!ius ith matter

%) Any nonrotating blac# hole

Ans& %'ection& 1(3

71.What name is given to a nonrotating blac# hole?A) A ormhole $) A 'charJschil! blac# hole

") A a#ing singularity %) A Herr blac# hole

Ans& $'ection& 1(3

7*.What name is given to a rotating blac# hole?

A) A 'charJschil! blac# hole $) A ormhole") A a#ing singularity %) A Herr blac# hole

Ans& %

'ection& 1(3

7,.What is a Herr blac# hole?

A) Any nonrotating blac# hole $) Any uncharge! blac# hole") Any rotating blac# hole %) A hypothetical Jeromass blac# hole

Ans& "

'ection& 1(3

7(.o !oes a Herr blac# hole !iffer from a 'charJschil! blac# hole?

A) Herr blac# holes have infinite mass2 'charJschil! blac# holes !o not.

") Herr blac# holes have net electric charge2 'charJschil! blac# holes !o not.$) Herr blac# holes have accretion !is#s2 'charJschil! blac# holes !o not.

%) Herr blac# holes rotate2 'charJschil! blac# holes !o not.

Ans& %'ection& 1(3

73.The !ifference beteen a 'charJschil! blac# hole


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$) The inner part of the accretion !is# here M rays are generate!

%) The region beteen the event horiJon an! the singularity from hich nothing can

escapeAns& A

'ection& 1(3

77.0n reference to blac# holes+ the or! ergosphere/ refers to

A) the entire region insi!e the event horiJon.

") a region just outsi!e the event horiJon of a rotating blac# hole here it isimpossible for anything to remain at rest.

$) the entire universe outsi!e the blac# hole.

%) the region occupie! by the accretion !is# here matter from a companion star

collects aroun! a blac# hole.Ans& "

'ection& 1(3

7=.@ne !ay+ hile straying !angerously close to a blac# hole+ you notice that you must #eepyour spaceship moving. :o matter ho har! you try to remain at rest+ you are inevitably

!ran into the blac# hole unless you #eep moving. What !oes this tell you about theblac# hole meters+ a little larger than the 'un

") *( AP+ a little larger than Fupiter-s orbit

$) 8.>3 pc+ more than half the !istance to the nearest star %) 1588 pc+ about onetenth of the ay across our Ialaxy

Ans& "

'ection& Toolbox 1(1

=1.A space freighter acci!entally !rops a steel beam hile passing a blac# hole+ an! the

beam starts falling toar! the blac# hole ith the long !irection of the beam pointing

toar! the blac# hole. What happens to the beam as it approaches the event horiJon?A) 0t expan!s in all !imensions to the siJe of the blac# hole event horiJon hen it

reaches this !istance from the singularity.

") 0t is stretche! in length an! compresse! in i!th.

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$) 0t is compresse! in both length an! i!th.

%) 0t is compresse! in length an! stretche! in i!th.

Ans& "'ection& 1(5

=*.What oul! happen to the gravitational force on the Earth if the 'un ere to be replace!by a 1solarmass blac# hole?

A) 0t oul! become extremely high+ sufficient to pull the Earth into it.

") 0t oul! !ouble in strength.$) 0t oul! remain as it is no.

%) 0t oul! be much less because the gravitational fiel! of a blac# hole only exists

very close to it.

Ans& $'ection& 1(5

=,.0f the 'un ere replace! by a 1solarmass blac# hole+ then the Earth oul!

A) enter an elliptical orbit passing close to the blac# hole+ ith its farthest !istancefrom the blac# hole equal to 1 AP.

") spiral quic#ly into the blac# hole.$) hea! off into interstellar space along a straightline tangent to its original orbit

aroun! the 'un.

%) continue to orbit the blac# hole in precisely its present orbit.Ans& %

'ection& 1(5

=(.As you are investigating a blac# hole from a safe !istance+ a rivet pops out of the tailfinon your spaceship an! falls toar! the blac# hole. Will you ever see the rivet enter the

event horiJon?

A) 6es+ but it ill be so blueshifte! that you oul! nee! Mray eyes to see it.") :o+ it ill be compresse! to Jero siJe an! !isappear from sight before it reaches the

event horiJon.

$) 6es+ you ill see it fall faster an! faster until it !isappears as it falls through theevent horiJon.

%) :o+ it ill appear to stop an! hover forever before entering the event horiJon.

Ans& %

'ection& 1(5

=3.A laborer repairing the cloc#toer on a space station orbiting a blac# hole acci!entally

!rops the cloc# in such a ay that it accelerates toar! the blac# hole. What !oes thisperson see hile atching the cloc#?

A) The han!s of the cloc# #eep normal time since time is absolute an! the same

everyhere.") The han!s of the cloc# move sloer an! sloer until they an! the cloc# itself stop

at the event horiJon.

$) As the cloc# nears the event horiJon+ the han!s begin to move ran!omly as time

becomes jumble! near the blac# hole.

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%) The han!s of the cloc# move faster an! faster until the cloc# plunges through the

event horiJon.

Ans& "'ection& 1(5

=5.What appears to happen to a cloc# as it approaches an! reaches the event horiJon aroun!a blac# hole hen viee! by a remote observer?

A) Time appears to pass at a much faster rate+ this rate becoming infinitely fast at the

event horiJon.") 0t appears to slo !on an! stop.

$) 0t spee!s up because of the intensifie! gravitational fiel!.

%) 0t tic#s uniformly since nothing changes the progress of time.

Ans& "'ection& 1(5

=7.0f you ere atching a frien! .Which of the folloing statements correctly !escribes cosmic censorship/?

A) "lac# holes cannot have magnetic fiel!s.

") All properties of the matter insi!e a blac# hole are hi!!en by the event horiJon+except for the total mass of the matter.

$) The amount of mass in a blac# hole can never be measure!.

%) :othing can leave a local region of space that contains a singularity.Ans& %

'ection& 1(5

>8.6ou gui!e your spacecraft into an orbit a fe AP from a blac# hole. 6ou #no its mass

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is ( or 3 solar masses+ but you ant to measure it more precisely. o oul! you !o

this?

A) Actually+ the mass of a blac# hole cannot be !etermine! precisely because it isimpossible to see beyon! the event horiJon. 'o your estimate of ( or 3 solar

masses is as goo! a value as you can hope for.

") 6ou can measure the perio! an! the semimajor axis of your orbit an! then use:eton-s form of Hepler-s thir! la.

$) 6ou cannot use :eton-s form of the thir! la. "ecause of general relativity+ you

must use a relativistic form of Hepler-s thir! la.%) 6ou must move in toar! the blac# hole an! mar# the !istance as you cross the

event horiJon. rom this !istance+ the mass can be calculate!.

Ans& "

'ection& 1(5

>1.A light ave is emitte! from the accretion !is# surroun!ing a blac# hole an! moves

toar! the hole an! aay from an observer. This observer ill see

A) the beam of light moving faster than cas it accelerates toar! the hole.") the beam of light slo !on an! stop as it reaches the event horiJon.

$) that the avelength of the light is gravitationally blueshifte! an! %opplerre!shifte!+ an! the to effects just cancel as the light reaches the event horiJon.

%) that the avelength of the light is gravitationally blueshifte! as it falls toar! the

event horiJon.Ans& %

'ection& 1(5

>*.Which effects have been useful


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Ans& %

'ection& 1(7

>(.Which of the folloing techniques has been successful in i!entifying goo! can!i!ates for

a blac# hole in our Ialaxy?

A) The !etection of extremely re!shifte! starlight from a region in the nearby spiralarm of the Ialaxy

") The !etection of M rays from a binary star un!ergoing mass exchange+ here

masses of component stars can be !etermine!$) The !etection of an extremely !ar# point in the s#y from hich no light at all is

seen

%) The gravitational lensing of light from a !istant object by the blac# hole to pro!uce

to i!entical imagesAns& "

'ection& 1(7

>3.What metho! is use! by astronomers to infer the existence in space of a !ar# object itha mass of about 3 solar masses+ such as a blac# hole?

A) The infrare! imaging of a region hose effective temperature is loer than thecosmic microave bac#groun!+ ren!ering it !ar#

") The measurement of the gravitational re!shift of spectral lines in the spectrum of

the object$) The measurement of the effect of its gravitational force on a companion object in a

binary system

%) The estimation of the luminosity of the object an! the application of the mass

luminosity relationshipAns& $

'ection& 1(7

>5.0 alays thought nothing coul! escape from a blac# hole+ yet astronomers are locating

blac# hole can!i!ates by the M rays they emit. o can M rays be coming from a blac#

hole?A) The M rays come from a highly compresse! region in an accretion !is# outsi!e the

event horiJon of the blac# hole.

") M rays are not light or matter an! can therefore escape from insi!e the blac# hole.

$) 0f the blac# hole is rotating+ it mo!ifies spacetime aroun! it so much that particlesan! M rays are create! in the vacuum just outsi!e the event horiJon.

%) The M rays are pro!uce! by vibrations of the blac# hole itself an! therefore !o not

come from insi!e the blac# hole.Ans& A

'ection& 1(7

>7.M rays that come from the vicinity of a blac# hole actually originate

A) from just outsi!e the event horiJon+ on the accretion !is#.

") from its exact center+ or singularity.

$) from relatively far aay from the blac# hole+ here matter is quite cool.

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%) from ell insi!e the event horiJon.

Ans& A

'ection& 1(7

>=.0f a blac# hole is truly blac# an! the escape velocity associate! ith this blac# hole is

greater than the spee! of light such that no light can escape it+ here !o the M rays fromthe blac# hole can!i!ates so far i!entifie! originate?

A) The blac# hole is only blac# to visible ra!iation+ but M rays travel faster than the

spee! of light an! so can escape.") They originate from the normal star accompanying the blac# hole+ its or!inary light

being blueshifte! into the Mray spectral region by the intense gravity of the blac#

hole.

$) They originate from stars behin! the blac# hole+ the light from hich is focuse!an! concentrate! such that it becomes Mray ra!iation by gravitational focusing.

%) They originate from the matter surroun!ing the blac# hole that is highly con!ense!

an! hence very hot because of the intense gravitational fiel!.

Ans& %'ection& 1(7

>>.The intense M rays emitte! by a suspecte! blac# hole are generate! by hat physical

mechanism?

A) "lueshifting of light emitte! by hot gas into the Mray region of theelectromagnetic spectrum by the extreme spee! of the gas moving into the blac#

hole

") 0n!uce! emission in atoms by the intense gravitational fiel! as material moves

toar! the blac# hole$) $ompressional heating as material moves into the hole

%) The !eceleration of matter as it abruptly stops at the event horiJon of the blac# hole

Ans& $'ection& 1(7

188.o has the !iameter of the blac# hole can!i!ate $ygnus M1 been estimate!?A) rom its angular siJe in the s#y an! its #non !istance

") rom the time scale of flic#ering of the M rays emitte! by it

$) rom its orbital perio! aroun! a companion star

%) rom the length of time it bloc#s off the light from its companion star hen itpasses in front of


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%) the shortness of its orbital perio!.

Ans& A

'ection& Iui!e! %iscovery& 0!entifying 'tellarQemnant "lac# oles+ $h.1(

18*.@ne object that is believe! to be a blac# hole in our Ialaxy is

A) the central star in the $rab :ebula.") the central star in the planetary nebula+ the Qing :ebula in Dyra.

$) the Gela pulsar.

%) $ygnus M1+ a poerful Mray source.Ans& %


18,.o as the blac# hole can!i!ate $ygnus M1 first !iscovere!?A) "y extremely high spatial resolution ra!io observations ith the GDA ra!io

interferometric array in :e 4exico

") "y highresolution visiblelight observations ith the ubble 'pace Telescope

$) "y Mray measurements ith the Phuru satellite%) "y infrare! observations ith the 0QA' infrare! satellite

Ans& $'ection& Iui!e! %iscovery& 0!entifying 'tellarQemnant "lac# oles+ $h.1(

18(.o has the mass of the blac# hole can!i!ate $ygnus M1 been estimate!?A) rom the perio!ic obble it pro!uces in the spectral lines of a normal companion

star aroun! hich it orbits

") rom the gravitational re!shift+ here the more massive the object+ the greater the

re!shift of its spectral lines$) rom the observe! siJe an! estimate! !ensity of the object

%) rom the perio!ic obble in its on characteristic blac#hole spectrum

Ans& A'ection& Iui!e! %iscovery& 0!entifying 'tellarQemnant "lac# oles+ $h.1(

183.Why is $ygnus M1 thought to be a blac# hole?A) 0t emits M rays that flic#er on time scales of onehun!re!th of a secon!+ a unique

characteristic of a blac# hole.

") :o light has ever been observe! to come from it.

$) 0t is smaller than the Earth+ but its mass is too large to be a neutron star or hite!arf.

%) 0t has pulle! matter from its companion star into an accretion !is# aroun! itself.

Ans& $'ection& Iui!e! %iscovery& 0!entifying 'tellarQemnant "lac# oles+ $h.1(

185.What is believe! to be the mass of the blac# hole can!i!ate $ygnus M1?A) 1*8 solar masses ") ,8 solar masses $) 7 solar masses %) 1 solar mass

Ans& $


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187.What is believe! to be the mass of the blac# hole can!i!ate at the center of the galaxy

4=7?

A) , million solar masses $) ,88+888 solar masses") , billion solar masses %) ,88 solar masses

Ans& "

'ection& 1(=

18=.o as the mass of the can!i!ate blac# hole at the center of the galaxy 4=7 estimate!?

A) rom the amount of mass that is !isappearing into it every year") rom the perio!ic shift in the avelengths of spectral lines from a companion

object aroun! hich the blac# hole is orbiting

$) rom observations of the very high orbital spee! of objects close to this center

%) rom the intensity of M rays from it an! the frequency of flic#ering of the Mrayintensity

Ans& $

'ection& 1(=

18>.Where oul! you loo# for a supermassive blac# hole?

A) 0n the center of a galaxy $) @rbiting a normal star in our Ialaxy") At the center of the universe %) At the center of a supernova remnant

Ans& A

'ection& 1(=

118.0n a ubble 'pace Telescope search for evi!ence of supermassive blac# holes in about ,8

nearby galaxies+ evi!ence as foun! that

A) only one galaxy+ our on 4il#y Way Ialaxy+ contains such a blac# hole.") no galaxies in our vicinity contain such a blac# hole at their centers.

$) almost all galaxies contain such blac# holes.

%) only spiral galaxies contain supermassive blac# holes.Ans& $

'ection& 1(=

111.What is a primor!ial blac# hole?

A) A blac# hole create! !uring the formation of the universe

") Any blac# hole not in orbit aroun! a normal star

$) A blac# hole create! !uring the formation of the solar system%) A blac# hole at the center of a galaxy

Ans& A

'ection& 1(=

11*.What name is given to any blac# hole that might have been create! in the "ig "ang at the

beginning of the universe?A) A supermassive blac# hole $) A Herr blac# hole

") A 'charJschil! blac# hole %) A primor!ial blac# hole

Ans& %

'ection& 1(=

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11,.Ias can be pulle! off a binary companion by a blac# hole. The blac# hole-s event

horiJon is too small to allo all of the gas to enter perpen!icularly+ so it orbits in a ringaroun! the blac# hole or a neutron star. What is this ring calle!?

A) A gas ring ") A Herr !is# $) An accretion !is# %) An ergoregion

Ans& $'ection& 1(>

11(.Ias jets have often forme! perpen!icular to the plane of the accretion !is# aroun! a blac#hole or a neutron star. What is it that propels the gas aay from the hole or star?

A) 4agnetic forces from the object-s strong magnetic fiel!

") $onservation of momentum since the outgoing particles are pair pro!uce! as

virtual particles near the object$) The enormous pressure of the compresse! infalling gas of the accretion !is#

%) The strong curvature of spacetime near the object

Ans& $

'ection& 1(>

113.What is the observe! !istribution of the longerliving gammaray bursters in the s#y?A) $oncentrate! primarily along the plane of the 4il#y Way+ in!icating an origin

ithin our Ialaxy

") Pniform over the entire s#y+ in!icating an origin at cosmological/ !istances$) $lumpy but not coinci!ing ith any #non galaxy clusters+ in!icating an origin in

a ne #in! of astronomical object

%) $lumpy+ approximately coinci!ing ith large clusters of galaxies such as the $oma

clusterAns& "

'ection& 1(18

115.What is the observe! !istribution of the shorterliving gammaray bursters in the s#y?

A) $oncentrate! primarily along the plane of the 4il#y Way+ in!icating an origin

ithin our Ialaxy") Pniform over the entire s#y+ in!icating an origin at cosmological/ !istances

$) $lumpy but not coinci!ing ith any #non galaxy clusters+ in!icating an origin in

a ne #in! of astronomical object

%) $lumpy+ approximately coinci!ing ith large clusters of galaxies such as the $omacluster

Ans& A

'ection& 1(18

117.@ur efforts to relate gammaray bursts ith specific sources has ha! hat results so far?

A) Iammaray bursters alays occur in the !epths of space+ far from any galactic orother obvious source.

") Iammaray bursters alays occur in the centers of galaxies+ inclu!ing those

observe! in the 4il#y Way Ialaxy.

$) Iammaray bursters appear to occur in galaxies+ but notat the centers of galaxies.

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%) Iammaray bursters occur in globular clusters+ ell aay from the main regions in

the host galaxy.

Ans& $'ection& 1(18

11=.What is the typical !uration of a gammaray burst?A) 'everal !ays+ in!icating a siJe much smaller than the !istance from the Earth to the

nearest star beyon! the 'un

") Dess than a couple of minutes+ in!icating a source smaller than 4ercury-s orbit$) Pp to about 1 hour+ in!icating a source less than half the siJe of our solar system

%) 'everal hours+ in!icating a source somehat larger than our solar system

Ans& "

'ection& 1(18

11>.What property of the longerliving gammaray bursters in!icates that they are locate! at

large


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1**.What is a virtual particle?

A) A particle hose existence is too short for us to #no it ever existe!

") A particle that never !oes anything rong$) A particle that+ if it comes in contact ith or!inary matter+ ill annihilate to form

pure energy

%) Any particle+ li#e a photon or a graviton+ that is ma!e up of avesAns& A

'ection& (5 an! 1(11

1*,.'ometimes particleantiparticle pairs are create! an! then annihilate so quic#ly that e

cannot #no that they ever existe!. What are these particles


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1*7.What oul! the mass of a primor!ial blac# hole nee! to have been in or!er for it to be

just !isappearing no+ !ue to the loss of a#ing ra!iation?A) 18 #g ") 18 million #g $) 18+888 #g %) 18 billion #g

Ans& %

'ection& 1(11

1*=.Which one of the folloing statements about the evaporation of blac# holes is correct?

A) The rate at hich a blac# hole evaporates is loer for a highermass blac# hole.") The rate at hich a blac# hole evaporates is higher for a highermass blac# hole.

$) "lac# holes !o not evaporate.

%) The rate at hich a blac# hole evaporates is in!epen!ent of the mass of the blac#

hole.Ans& A

'ection& 1(11

1*>.4atter in an accretion !is# is in orbit aroun! a blac# hole+ but friction ithin the !is#causes the matter to gra!ually spiral into the blac# hole. What ill change in terms of the

observable properties of the blac# hole as this process continues?A) @nly the mass ill increase.

") The mass+ the angular momentum+ an! the rate of evaporation of the blac# hole ill

increase.$) :othing ill change.

%) "oth the mass an! the angular momentum of the blac# hole ill increase.

Ans& %

'ection& 1(11

astronomy - chapter 14 test

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