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Class:AST 192 - STARS, GALAXIES AND THE UNIVERSE
Subject:Astronomy
University:University of Kentucky
Term:Spring 2010
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where in a red giant star is nuclear energy released? in a thin shell around the core
if the sun loses some of its mass as a red giant the orbits of the planets become... larger
for approximately how long will the sun be a main sequence star? 11 billion years
in 1.1 billion years, what will happen to the sun? the suns luminosity rises 10% and all life on Earth is destroyed
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in 6.5 billion years, what will happen to the sun? it's main sequence phase will end
in 7.8 billion years, what will happen to the sun? it will become a red giant and lose 25% of its mass
in 7.9 billion years, what will happen to the sun? the onset of He --> C fusion in the core and the red giant phase ends, and the sun becomes an He fusing star
in 8 billion years, what will happen to the sun all He in the core is exhausted and the sun develops into a red supergiant and loses another 25% of its mass
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the first phase of the star is ____. protostar
during the phase in which the sun is a protostar, does gravitational contraction occur? yes
what ends the protostar phase? the onset of H-->He in core
what is the second phase in the suns lifetime? main sequence
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is there gravitational contraction during the main sequence phase no
what ends the main sequence phase? exhaustion of H in core
what is the third phase in the sun's lifetime? red giant
what is the principal fusion in the red giant phase? H --> He in the shell
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is there gravitational contraction in the red giant phase? yes
what ends the red giant phase? onset of He --> C in the core
what is the fourth stage in the suns lifetime? He fusing star
is there gravitational contraction while the sun is a He fusing star? no
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what ends the He fusing star phase? exhaustion of He in core
What is the fifth phase in the sun's lifetime? red supergiant
what is the fusion reaction in the red supergiant phase? He --> C in shell
is there gravitational contraction in the red supergiant phase? yes
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what temperature is required for the sun to become a He fusing star? 100 million K
Do diameter and luminosity decline when the sun becomes a He fusing star? Yes
what event will end the Sun's red giant phase? onset of fusion reactions in the core
gravitational contraction _____ occur in the core of an He fusing star because____ does not, fusion occurs in the core
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what phase in the lifetime of a star is most similar to the main sequence phase? He fusing?
after the red giant phase, the sun goes through a .... planetary nebula phase
is there a principal reaction or gravitational contraction in the planetary nebula phase? no and no
what event ends the planetary nebula phase? ejection of star's envelope
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what phase comes after the planetary nebula phase? the white dwarf phase
does a white dwarf have any source of nuclear energy? no
through which phases is the sun's lifetime similar with that of more massive main sequence stars? from protostar to red supergiant
what is the greatest possible mass of a white dwarf, in terms of the sun's current mass? 1.4
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as time progresses, the temperature of a white dwarf ___ and the diameter ____ decreases, remains the same
the life time of a star depends on what two factors? amount of fuel and fuel consumption rate
what property of a star is related to the amount of fuel it has available? mass
what property of a star is related to its fuel consumption rate? luminosity
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why do more massive stars have shorter lifetimes? because the are more luminous, therefore they use more of the fuel faster
in a more massive star, do core contractions stop in red supergiant phase? no
what is special about iron as far as nuclear fusion is concerned? it generates no energy in fusion
after the red supergiant phase of a massive star, what phase does it enter? a heavy element fusing phase
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which elements does a heavy element fusion star fuse? C, Ne, O, Si in the core
is there gravitational contraction in the heavy element fusion phase? at times
what ends the heavy element fusion phase? accumulation of Fe in core
what is the last phase of a massive star? supernova
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what occurs in this phase? catastrophic collapse and brief fusion reactions
what ends the supernova phase? destruction of the star
what happens the the temperature in a type two supernova? it increases in the core
what happens to protons and electrons in a type two supernova? they combine to form neutrinos
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what eventually halts the core collapse in a type two supernova? neurons
does the core become dense and incompressible in a type two supernova? yes
what is the star considered after a type two supernova? a neutron star
what event in the lifecycle of a massive star does not occur in the lifecycle of a lower mass star like the sun fusion of C to heavier elements in the core
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what is the last phase in a stars life time common to all stars? red supergiant
what particles are thought to make up the core of a star immediately prior to a supernova? iron nuclei and electrons
during the core collapse what occurs? Fe core collapses, creates neutron star
what happens after the core collapse? infall of the envelope
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what occurs after the infall of the envelope envelope rebounds off neutron star, creating outward moving shock
what occurs after the rebound of envelope stellar explosion: shock wave sweeps up envelope material, ejects it violently into space and the neutron star is visible
how can a supernova first be detected? neutrinos can be detected
what particles, produced during a supernova, escape rapidly from the star? neutrinos
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what particles are thought to make up the core of a massive star after the core collapse? neutrons
approximately how long after the core collapse in a supernova event would an external observer see the star explode? a few hours to a day
how often are supernovae estimated to occur in our galaxy? once or twice per century
why have we not seen more supernovae? most SN are in the disk of our galaxy and hidden by interstellar dust
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when was the last SN in our galaxy observed? 1604
are many other supernovae observed in other galaxies each year? yes
the first supernova seen with the naked eye since 1604 was in 1987. it was not in our galaxy. what was special about this event? first supernova for which we have info about the pre-supernova star and first supernova for which we detected neutrinos.
what star is predicted to be the next supernova star in our galaxy? Betelgeuse
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what are SN remnants? an expanding nebula of gas that was once inside a star
1. Why do we see on Earth only a small fraction of the supernovae that occur in our Galaxy? Supernovae are often obscured by dust in interstellar space.
2. The supernova observed in 1987 was visible to the naked eye. The supernova was unusual because… Neutrinos were observed from the supernova.
3. The supernova that created the Crab Nebula was observed in AD 1054. The supernova occurred about 6500 years ago. Therefore, the explosion actually occurred… 5500 BC
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do SN remnants emit light waves? yes
as gas of SNR expands outward into interstellar space, what does it mix with? interstellar material
what is the object called that is at the center of the crab Nebula? a pulsar
what does a pulsar do? emits very regular pulses of light and other radiation. in the crab nebula, this occurs about 30 times per second
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what is a pulsar thought to be? a rotating neutron star
which elements are less abundant in the universe? ones with higher atomic numbers
true/false: heavier elements are much rarer than lighter elements true
what three categories do elements fall in to? light, heavier, heaviest
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what object lies near the center of the Crab nebula? a neutron star
the object near the center of the crab nebula is unusual in that is... emits flashes of light regularly
where are heavier elements produced in the universe? in massive stars, near the end of their lifetimes
how do these elements become apart of the sun and planets supernovae released them into the interstellar medium and the sun and planets are formed partly from the recycled material
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why are elements heavier than iron so rare? they cannot be produced in stars during their ordinary lifetimes, only during supernovae when conditions are just right, which is only a brief period of time. therefore these elements are produced in small quantities
what are the lightest elements and how were they formed? H and He, and they have existed since the first few minutes after origin of universe
what are the heavier elements and how were they formed up to Fe and mostly produced in massive stars prior to supernovae.
what are the heaviest elements and how ere they formed up to Ur and they are produced briefly during supernovae
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what is cosmology? branch of astronomy concerned with the origin and evolution of the universe as a whole
what are the assumptions of cosmology? that our region of the universe is typical and that the universe is isotropic and homogenous
what does isotropic mean? same, on average, in all directions
what does homogenous mean? same, on average, in all location
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1. In the argument known as Olbers Paradox, a conclusion is drawn that is contrary to the truth. What is this false conclusion? the sky is bright everywhere
what is an assumption about the universe that is part of Olbers Paradox? the universe is infinite
Supposed that matter in the universe only exists out to a certain distance, beyond which there is a void. therefore the universe cannot be… homogenous
what is olbers paradox? • If the universe is… ○ Infinite ○ Populated throughout by shining stars and galaxies • Then there should be a star in every direction, the sky should be as bright as the Sun everywhere.
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if the universe only extends out so far, then it cannot also be... homogenous
if the universe was born at a specific time in the past, has light from extremely distant stars and galaxies had time to reach us? not yet
is the presently observable universe finite, even if the universe is infinite? yes
what is the modern resolution to olbers paradox? that the universe formed at some specific time in the past
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how have astronomers measured the motions of galaxies? via Doppler Effect
what has the Doppler Effect shown? that all galaxies, except for a few nearby ones, are moving away from us
are more distant galaxies moving faster? yes
are recession velocities proportional to their distances? yes
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what is Hubble Law? v = H0d V= velocity H0 = Hubble constant (approx. 20 km/s) d = distance
• If a galaxy is now 100 million ly away, how fast is it receding from us? 2000 km/s
are stars, galaxies or clusters of galaxies expanding? no, only the distances between them
are we the center of expansion not necessarily
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where were distant galaxies when the universe was born? close together
what is the current estimated age of the universe? about 14 billion years
the Hubble Law describes what property of the universe? expansion
Hubble constant is about 20km/s per million ly of distance. in this case, how fast should a galaxy be moving relative to us if its distance is 10 million ly? 200 km/s
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what info can astronomers infer about the universe from the Hubble Law? the age of the universe
what were the conditions of the universe when first born? very hot and dense. cooled down with time
what occurred a fraction of a second after time 0? the universe was a nearly uniform soup of particles and radiation. there was very little structure
what occurred a few minutes after time 0 rapid expansion caused temperature and density to drop drastically and nuclear fusion creates some helium
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what occurred much later after time 0? galaxies and stars began to form in the still expanding universe
is the universe still expanding today? yes
is the universe filled with radiation that existed shorter after time 0 yes, cosmic background radiation was discovered in 1965
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 where in a red giant star is nuclear energy released?in a thin shell around the core
 if the sun loses some of its mass as a red giant the orbits of the planets become...larger
 for approximately how long will the sun be a main sequence star?11 billion years
 in 1.1 billion years, what will happen to the sun?the suns luminosity rises 10% and all life on Earth is destroyed
 in 6.5 billion years, what will happen to the sun?it's main sequence phase will end
 in 7.8 billion years, what will happen to the sun?it will become a red giant and lose 25% of its mass
 in 7.9 billion years, what will happen to the sun?the onset of He --> C fusion in the core and the red giant phase ends, and the sun becomes an He fusing star
 in 8 billion years, what will happen to the sunall He in the core is exhausted and the sun develops into a red supergiant and loses another 25% of its mass
 the first phase of the star is ____.protostar
 during the phase in which the sun is a protostar, does gravitational contraction occur?yes
 what ends the protostar phase?the onset of H-->He in core
 what is the second phase in the suns lifetime?main sequence
 is there gravitational contraction during the main sequence phaseno
 what ends the main sequence phase?exhaustion of H in core
 what is the third phase in the sun's lifetime?red giant
 what is the principal fusion in the red giant phase?H --> He in the shell
 is there gravitational contraction in the red giant phase?yes
 what ends the red giant phase?onset of He --> C in the core
 what is the fourth stage in the suns lifetime?He fusing star
 is there gravitational contraction while the sun is a He fusing star?no
 what ends the He fusing star phase?exhaustion of He in core
 What is the fifth phase in the sun's lifetime?red supergiant
 what is the fusion reaction in the red supergiant phase?He --> C in shell
 is there gravitational contraction in the red supergiant phase?yes
 what temperature is required for the sun to become a He fusing star?100 million K
 Do diameter and luminosity decline when the sun becomes a He fusing star?Yes
 what event will end the Sun's red giant phase?onset of fusion reactions in the core
 gravitational contraction _____ occur in the core of an He fusing star because____does not, fusion occurs in the core
 what phase in the lifetime of a star is most similar to the main sequence phase?He fusing?
 after the red giant phase, the sun goes through a ....planetary nebula phase
 is there a principal reaction or gravitational contraction in the planetary nebula phase?no and no
 what event ends the planetary nebula phase?ejection of star's envelope
 what phase comes after the planetary nebula phase?the white dwarf phase
 does a white dwarf have any source of nuclear energy?no
 through which phases is the sun's lifetime similar with that of more massive main sequence stars?from protostar to red supergiant
 what is the greatest possible mass of a white dwarf, in terms of the sun's current mass?1.4
 as time progresses, the temperature of a white dwarf ___ and the diameter ____decreases, remains the same
 the life time of a star depends on what two factors?amount of fuel and fuel consumption rate
 what property of a star is related to the amount of fuel it has available?mass
 what property of a star is related to its fuel consumption rate?luminosity
 why do more massive stars have shorter lifetimes?because the are more luminous, therefore they use more of the fuel faster
 in a more massive star, do core contractions stop in red supergiant phase?no
 what is special about iron as far as nuclear fusion is concerned?it generates no energy in fusion
 after the red supergiant phase of a massive star, what phase does it enter?a heavy element fusing phase
 which elements does a heavy element fusion star fuse?C, Ne, O, Si in the core
 is there gravitational contraction in the heavy element fusion phase?at times
 what ends the heavy element fusion phase?accumulation of Fe in core
 what is the last phase of a massive star?supernova
 what occurs in this phase?catastrophic collapse and brief fusion reactions
 what ends the supernova phase?destruction of the star
 what happens the the temperature in a type two supernova?it increases in the core
 what happens to protons and electrons in a type two supernova?they combine to form neutrinos
 what eventually halts the core collapse in a type two supernova?neurons
 does the core become dense and incompressible in a type two supernova?yes
 what is the star considered after a type two supernova?a neutron star
 what event in the lifecycle of a massive star does not occur in the lifecycle of a lower mass star like the sunfusion of C to heavier elements in the core
 what is the last phase in a stars life time common to all stars?red supergiant
 what particles are thought to make up the core of a star immediately prior to a supernova?iron nuclei and electrons
 during the core collapse what occurs?Fe core collapses, creates neutron star
 what happens after the core collapse?infall of the envelope
 what occurs after the infall of the envelopeenvelope rebounds off neutron star, creating outward moving shock
 what occurs after the rebound of envelopestellar explosion: shock wave sweeps up envelope material, ejects it violently into space and the neutron star is visible
 how can a supernova first be detected?neutrinos can be detected
 what particles, produced during a supernova, escape rapidly from the star?neutrinos
 what particles are thought to make up the core of a massive star after the core collapse?neutrons
 approximately how long after the core collapse in a supernova event would an external observer see the star explode? a few hours to a day
 how often are supernovae estimated to occur in our galaxy?once or twice per century
 why have we not seen more supernovae?most SN are in the disk of our galaxy and hidden by interstellar dust
 when was the last SN in our galaxy observed?1604
 are many other supernovae observed in other galaxies each year?yes
 the first supernova seen with the naked eye since 1604 was in 1987. it was not in our galaxy. what was special about this event?first supernova for which we have info about the pre-supernova star and first supernova for which we detected neutrinos.
 what star is predicted to be the next supernova star in our galaxy?Betelgeuse
 what are SN remnants?an expanding nebula of gas that was once inside a star
 1. Why do we see on Earth only a small fraction of the supernovae that occur in our Galaxy? Supernovae are often obscured by dust in interstellar space.
 2. The supernova observed in 1987 was visible to the naked eye. The supernova was unusual because… Neutrinos were observed from the supernova.
 3. The supernova that created the Crab Nebula was observed in AD 1054. The supernova occurred about 6500 years ago. Therefore, the explosion actually occurred… 5500 BC
 do SN remnants emit light waves?yes
 as gas of SNR expands outward into interstellar space, what does it mix with?interstellar material
 what is the object called that is at the center of the crab Nebula?a pulsar
 what does a pulsar do?emits very regular pulses of light and other radiation. in the crab nebula, this occurs about 30 times per second
 what is a pulsar thought to be?a rotating neutron star
 which elements are less abundant in the universe?ones with higher atomic numbers
 true/false: heavier elements are much rarer than lighter elementstrue
 what three categories do elements fall in to?light, heavier, heaviest
 what object lies near the center of the Crab nebula?a neutron star
 the object near the center of the crab nebula is unusual in that is...emits flashes of light regularly
 where are heavier elements produced in the universe?in massive stars, near the end of their lifetimes
 how do these elements become apart of the sun and planetssupernovae released them into the interstellar medium and the sun and planets are formed partly from the recycled material
 why are elements heavier than iron so rare?they cannot be produced in stars during their ordinary lifetimes, only during supernovae when conditions are just right, which is only a brief period of time. therefore these elements are produced in small quantities
 what are the lightest elements and how were they formed?H and He, and they have existed since the first few minutes after origin of universe
 what are the heavier elements and how were they formedup to Fe and mostly produced in massive stars prior to supernovae.
 what are the heaviest elements and how ere they formedup to Ur and they are produced briefly during supernovae
 what is cosmology?branch of astronomy concerned with the origin and evolution of the universe as a whole
 what are the assumptions of cosmology?that our region of the universe is typical and that the universe is isotropic and homogenous
 what does isotropic mean?same, on average, in all directions
 what does homogenous mean?same, on average, in all location
 1. In the argument known as Olbers Paradox, a conclusion is drawn that is contrary to the truth. What is this false conclusion? the sky is bright everywhere
 what is an assumption about the universe that is part of Olbers Paradox?the universe is infinite
 Supposed that matter in the universe only exists out to a certain distance, beyond which there is a void. therefore the universe cannot be… homogenous
 what is olbers paradox?• If the universe is…
○ Infinite
○ Populated throughout by shining stars and galaxies
• Then there should be a star in every direction, the sky should be as bright as the Sun everywhere.
 if the universe only extends out so far, then it cannot also be...homogenous
 if the universe was born at a specific time in the past, has light from extremely distant stars and galaxies had time to reach us? not yet
 is the presently observable universe finite, even if the universe is infinite?yes
 what is the modern resolution to olbers paradox?that the universe formed at some specific time in the past
 how have astronomers measured the motions of galaxies?via Doppler Effect
 what has the Doppler Effect shown?that all galaxies, except for a few nearby ones, are moving away from us
 are more distant galaxies moving faster?yes
 are recession velocities proportional to their distances?yes
 what is Hubble Law?v = H0d

V= velocity
H0 = Hubble constant (approx. 20 km/s)
d = distance
 • If a galaxy is now 100 million ly away, how fast is it receding from us? 2000 km/s
 are stars, galaxies or clusters of galaxies expanding?no, only the distances between them
 are we the center of expansionnot necessarily
 where were distant galaxies when the universe was born?close together
 what is the current estimated age of the universe?about 14 billion years
 the Hubble Law describes what property of the universe?expansion
 Hubble constant is about 20km/s per million ly of distance. in this case, how fast should a galaxy be moving relative to us if its distance is 10 million ly?200 km/s
 what info can astronomers infer about the universe from the Hubble Law?the age of the universe
 what were the conditions of the universe when first born?very hot and dense. cooled down with time
 what occurred a fraction of a second after time 0?the universe was a nearly uniform soup of particles and radiation. there was very little structure
 what occurred a few minutes after time 0rapid expansion caused temperature and density to drop drastically and nuclear fusion creates some helium
 what occurred much later after time 0?galaxies and stars began to form in the still expanding universe
 is the universe still expanding today?yes
 is the universe filled with radiation that existed shorter after time 0yes, cosmic background radiation was discovered in 1965
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