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Universities » University of Kentucky (UK) » AST - Astronomy » 192 - STARS, GALAXIES AND THE UN.. » Flash Cards

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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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the sun was previously what kind of star? protostar (undergoing gravatational contraction?
the sun is currently a main sequence star generating.... energy via. fusion H --> He in its core
age of sun and entire solar system... 4.5 billion years (estimate made from ages of meteorites)
Proto star no principle fusion gravitational contraction throughout onset of H --> He in core
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Main sequence H --> He in core no gravatational contraction exhaustion of H in core leads to end of phase
Red giant h --> he in shell gravatational contraction in core onset of He --> C in core
He-fusing star He --> C in core no gravatational contraction exhausting of He in core
red super giant He --> in C in shell gravitational contraction in core end of core contraction
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planetary nebula no gravatational contraction ejection of stars envelope
white dwarf no fusion reaction no gravitational contraction no event ending phase
what must eventually happen in the core of the sun? H fusion in core ceases once H is exhausted suns mainsequence lifetime ends
why does He --> C not immediately begin in core? Core temp. not high enough
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what process must begin in core of sun? (at end of main sequence phase) core begins gravatational contraction and core temp slowly rises
what element is not must abundant in sun's core? (at end of main sequence phase) He - H is now exhausted in core by fusion
transforming to red giant... shell- becomes hotter via contact with core luminosity of star rises rising luminosity pushes envelope outward
where in a red giant star is nuclear energy released? the think shell about the core
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if the sun loses some of its mass as a red giant, the orbit of the planets will... become larger
for approimately how long will the sun be a main sequence star (i.e. start to finish of this phase?) 11 billion yrs
life cycle of sun 0.0 present
life cycle of sun 6.5 billion yrs sun will not be a main sequence star anymroe
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what happens next in the contracting He core (once it hits 100 million k?) He --> C fusion begins -stars structure profoundly changes diameter -luminosity greatly declines -sun becomes a He fusing star
why should He fusing phase be much shorter than main sequence phase? He --> C generates much less energy that H --?he so He-->C sustains star for much shorter time
He fusing star last... 0.1 billion yrs
what must happen in C core (once He exhausted?) gravatational contraction begins again in core -star becomes a red giant again
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suns life cycle 7.8 billion yrs sun a fully developed red giant loses 25% of its mass
life cycle of sun 7.9 billion yrs onset of He -->C in core ends red girant phase sun becomes a He --> fusing star
life cycle of sun 8 billion yrs He in core exhausted sun developes into red supergiant loses another 25% of its mass
what event should end red super giant phase of suns lifetime? growing contraction
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by the time the sun becomes a red super giant its core will be so dense it can contract no more why? electron in core strongly resist further compression
what event will end the suns red giant phase onset of fusion reactions in the core
gracatatonal contraction _______ occur in the core of a 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
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life cycle of sun 8.02 suns outer layer form planetary nebula core becomes white dwarf
suns main sequence lifetime last.... 90% of total lifetime
white dwarf very small -no source of nuclear energy -gradually cools off
all stars go through same sequence of phases from protostar to red supergiant
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main sequence star has 5 times the suns mass &100 time the suns luminosity estimated main sequence lifetime for such a star is __ times the sums main sequence lifetimesequence 1/20th
consider stars visible today with 25 times the mass of the sun
low mass stars- .5 solar masses
high mass stars 25 solar masses
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fate of massive star -core contraction does not stop in red supergiant -core contraction continues until next fusion reaction begins
life of massive star h -->he core temp 40 million core density 4 duration 7 million yrs
life of a massive star he -- CO core temp 200 million core density 600 duration 700,00 yrs
life of a massive star C --> Ne, Mg core temp 700 million core density 600,000 duration 200 yrs
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life of a massive star Ne --> O, Mg core temp 1 billion core density 4 million duration 6 months
life of a massive star O --> Si, S core temp 2 billion core density 10 million duration 6 months
life of a massive star Si --> Fe core temp 3 billion stars core density 100 million duration 1 day
what is special about iron (Fe) as far as nuclear fusion is concerned? Fe fusion generates no energy
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death of a massive star core collapses catastrophically triggering a supernova explosion that destroys the star.
what event in the life cycle of a massive star does not occur in the lifecycle of a low mass star life the sun? fusion of C to heavier elements in the core
what is the las phase in a stars lifetime that is common to all stars (high mass & low mass?) red supergiant
what particles are thought to make up the core of a massive star immediately prior to a supernova? iron nuclei and electrons
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what happens to envelpe after core collapse? envelope falls in the core -rebounds off core sends shockwave outward -once shockwave reaches surface star material blasts out into space -witness a supernova
core collapse- Fe core collapse, creates neutron star (20 mi diameter)
infall of envelope - envelope above neutron star falls onto neutron star
rebound of envelope- envelope rebounds off neutron star creates outward moving shock wave
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stellar explosion shock wave sweeps up envelope material ejects it violently into space neutron star becomes visible
what particles produced during a supernova escape rapidly from the star? neutrions
what particls are thought to make up the core of a massive star after the core collapses in a supernova event? neutrons
approximately how long after the core collapses in a supernova eent would an external observer see the star explode? a few hours to a day
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last supernova seen in our galaxy.... 1604
what have we not seen more supernovas? -most occur in disk of our gallaxy -most are hidden by interstellar dust
why do we see on earth only small fractions of the supernocva that occurs in our galaxy? ofter obscured by dust in interstellar space
the supernova observed in 1987 was visible to the naked eye...this was unusual because neutrons were observed through the supernova
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the supernova that created the crab nebula was observed in ad1054 about 6500 yrs ago therefore the explosion actually occured... 5500 BC
aftermaths of supernovas emit light radio waves -gas expands outward into interstellar space it mixes with the existing interstellar space it mixes with
what object lies near the center of the crab nebula? a neutron star
the object near the center of the crab nebula is unusal in that if? emits flashes of light regulary
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which chemical element is rarest in the universe at large? lead
where are heavier elements such as silicon, oxygen and iron produced in the universe? in massive stars
how did these elements become part of the sun and planets? supernova released these elements into the interstellar medium
lightest elements (h,he) have existed since when... first few minutes after origin of universe
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heavier elements (up to Fe) produced where? in massive stars prior to supernova
heaviest elements (up to Ur) produced where? briefly during supernova
cosmetology branch of astronomy concerned with the origin and evolution of universe as a whole
isotropic same (on average) in all directions
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in the argument known as olbers paradox a conclusion is drawn that is contrary to the truth what is the false conclusion? distance stars and galaxies are hidden by cosmic chest and the sky is bright everywhere.
what is an assumption about the universe that is part of olbers paradox? the universe is infinite
suppose that matter in the universe only exist out to a certain distance by beyond which there is a void in such case the universe cannot be? homogenous
olbers paradox review if the universe only extends out so far then it connot also be homogenous
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if the galaxy is now 100 million yrs away receding at 200 km/s how long did it take to get so far away? 15 billion yrs
The Sun contains all but about _____ of the total mass of the Solar System. 1/500th
The universe, according to the best available scientific evidence, is approximately _____ years old. 14 billion
The age of the Solar System, according to the best available scientific evidence, is approximately _____ the age of the universe 1/3rd
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The number of stars in the Solar System is 1
Homogenous same (on average)on all locations
If we assume that the universe is homogenous, then we imply that the universe_ Looks the same any from any location
Why is it that the sky is dark between the star? You should be able to see a star in every direction. More distant stars fill the sapces of the earer ones. Should be birght in every direction w/ no dark spots.
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Hubble Law - Recession Velocities (v) of distant galaxies are proportional to their distances (d). This is the Hubble Law: v=Hod; Constant= Ho- called the Hubble constant= 20km/s for each million LY of distant
If your roommate calls you and says she is near columbus OH, Which is 180 miles away, and she is traveling at 60 mph, how long ago did she leave lex? Time=distance/rate--> 180/60 = 3 hours ago
Suppose we had chosen a galaxy twice as far away, would the time estimate be the same? yes, since the Hubble law predicts twice the recession velocity. So the ration of distance/rate = the same
The Hubble law describes what property of the universe? Velocity; V=HoD
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The hubble constant is about 20 km/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 LYs? 200 km/s
what info can astronomers infer about the universe from the Hubble Law? The age of the universe
Big Bang Model -universe began at a fixed moment in time (time zero)-Matter, Space & time came into exsitence at time zero -universe initally very hot and dense with time it expanded and cooled-Big bang model describes how conditions changes in universe, beginning very shortly after time zero. -model makes predictions about nature of universe today.
-4.5 Billion Years Sun becomes main sequence star, planets newly formed
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At the end of the main sequence phase of the sun's lifetime, the core will be mostly composed of__ and the envelope will be composed of__ Helium, Hydrogen
What nuclear reaction will occur in the core of the sun immediately after its main sequence lifetime is over? None
Gravitational contraction always: 1. results in higher tempreature 2. continues until an internal energy source is available: .a Therefore: in the core of a star there is either 1. gravitational contraction or energy release via fusion reactions
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 the sun was previously what kind of star?protostar (undergoing gravatational contraction?
 the sun is currently a main sequence star generating....energy via. fusion
H --> He in its core
 age of sun and entire solar system...4.5 billion years
(estimate made from ages of meteorites)
 Proto starno principle fusion
gravitational contraction throughout
onset of H --> He in core
 Main sequence H --> He in core
no gravatational contraction
exhaustion of H in core leads to end of phase
 Red gianth --> he in shell
gravatational contraction in core
onset of He --> C in core
 He-fusing starHe --> C in core
no gravatational contraction
exhausting of He in core
 red super giantHe --> in C in shell
gravitational contraction in core
end of core contraction
 planetary nebulano gravatational contraction
ejection of stars envelope
 white dwarfno fusion reaction
no gravitational contraction
no event ending phase
 what must eventually happen in the core of the sun?H fusion in core ceases once H is exhausted
suns mainsequence lifetime ends
 why does He --> C not immediately begin in core?Core temp. not high enough
 what process must begin in core of sun? (at end of main sequence phase)core begins gravatational contraction
and core temp slowly rises
 what element is not must abundant in sun's core? (at end of main sequence phase)He - H is now exhausted in core by fusion
 transforming to red giant...shell- becomes hotter via contact with core
luminosity of star rises
rising luminosity pushes envelope outward
 where in a red giant star is nuclear energy released?the think shell about the core
 if the sun loses some of its mass as a red giant, the orbit of the planets will...become larger
 for approimately how long will the sun be a main sequence star (i.e. start to finish of this phase?)11 billion yrs
 life cycle of sun 0.0 present
 life cycle of sun 6.5 billion yrssun will not be a main sequence star anymroe
 what happens next in the contracting He core (once it hits 100 million k?)He --> C fusion begins
-stars structure profoundly changes diameter
-luminosity greatly declines
-sun becomes a He fusing star
 why should He fusing phase be much shorter than main sequence phase?He --> C generates much less energy that H --?he so He-->C sustains star for much shorter time
 He fusing star last...0.1 billion yrs
 what must happen in C core (once He exhausted?)gravatational contraction begins again in core
-star becomes a red giant again
 suns life cycle 7.8 billion yrssun a fully developed red giant loses 25% of its mass
 life cycle of sun 7.9 billion yrsonset of He -->C in core ends red girant phase sun becomes a He --> fusing star
 life cycle of sun 8 billion yrsHe in core exhausted sun developes into red supergiant loses another 25% of its mass
 what event should end red super giant phase of suns lifetime?growing contraction
 by the time the sun becomes a red super giant its core will be so dense it can contract no more why?electron in core strongly resist further compression
 what event will end the suns red giant phaseonset of fusion reactions in the core
 gracatatonal contraction _______ occur in the core of a 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
 life cycle of sun 8.02suns outer layer form planetary nebula core becomes white dwarf
 suns main sequence lifetime last....90% of total lifetime
 white dwarfvery small
-no source of nuclear energy
-gradually cools off
 all stars go through same sequence of phases from protostar to red supergiant 
 main sequence star has 5 times the suns mass &100 time the suns luminosity estimated main sequence lifetime for such a star is __ times the sums main sequence lifetimesequence 1/20th
 consider stars visible today with 25 times the mass of the sun 
 low mass stars-.5 solar masses
 high mass stars 25 solar masses
 fate of massive star-core contraction does not stop in red supergiant
-core contraction continues until next fusion reaction begins
 life of massive star h -->hecore temp 40 million
core density 4
duration 7 million yrs
 life of a massive star he -- COcore temp 200 million
core density 600
duration 700,00 yrs
 life of a massive star C --> Ne, Mgcore temp 700 million
core density 600,000
duration 200 yrs
 life of a massive star Ne --> O, Mgcore temp 1 billion
core density 4 million
duration 6 months
 life of a massive star O --> Si, Score temp 2 billion
core density 10 million
duration 6 months
 life of a massive star Si --> Fecore temp 3 billion stars
core density 100 million
duration 1 day
 what is special about iron (Fe) as far as nuclear fusion is concerned?Fe fusion generates no energy
 death of a massive starcore collapses catastrophically triggering a supernova explosion that destroys the star.
 what event in the life cycle of a massive star does not occur in the lifecycle of a low mass star life the sun?fusion of C to heavier elements in the core
 what is the las phase in a stars lifetime that is common to all stars (high mass & low mass?)red supergiant
 what particles are thought to make up the core of a massive star immediately prior to a supernova?iron nuclei and electrons
 what happens to envelpe after core collapse?envelope falls in the core
-rebounds off core sends shockwave outward
-once shockwave reaches surface star material blasts out into space
-witness a supernova
 core collapse-Fe core collapse, creates neutron star (20 mi diameter)
 infall of envelope -envelope above neutron star falls onto neutron star
 rebound of envelope-envelope rebounds off neutron star creates outward moving shock wave
 stellar explosionshock wave sweeps up envelope material ejects it violently into space neutron star becomes visible
 what particles produced during a supernova escape rapidly from the star?neutrions
 what particls are thought to make up the core of a massive star after the core collapses in a supernova event?neutrons
 approximately how long after the core collapses in a supernova eent would an external observer see the star explode?a few hours to a day
 last supernova seen in our galaxy....1604
 what have we not seen more supernovas?-most occur in disk of our gallaxy
-most are hidden by interstellar dust
 why do we see on earth only small fractions of the supernocva that occurs in our galaxy?ofter obscured by dust in interstellar space
 the supernova observed in 1987 was visible to the naked eye...this was unusual becauseneutrons were observed through the supernova
 the supernova that created the crab nebula was observed in ad1054 about 6500 yrs ago therefore the explosion actually occured...5500 BC
 aftermaths of supernovasemit light radio waves
-gas expands outward into interstellar space it mixes with the existing interstellar space it mixes with
 what object lies near the center of the crab nebula?a neutron star
 the object near the center of the crab nebula is unusal in that if?emits flashes of light regulary
 which chemical element is rarest in the universe at large?lead
 where are heavier elements such as silicon, oxygen and iron produced in the universe?in massive stars
 how did these elements become part of the sun and planets?supernova released these elements into the interstellar medium
 lightest elements (h,he) have existed since when...first few minutes after origin of universe
 heavier elements (up to Fe) produced where?in massive stars prior to supernova
 heaviest elements (up to Ur) produced where?briefly during supernova
 cosmetologybranch of astronomy concerned with the origin and evolution of universe as a whole
 isotropicsame (on average) in all directions
 in the argument known as olbers paradox a conclusion is drawn that is contrary to the truth what is the false conclusion?distance stars and galaxies are hidden by cosmic chest and the sky is bright everywhere.
 what is an assumption about the universe that is part of olbers paradox?the universe is infinite
 suppose that matter in the universe only exist out to a certain distance by beyond which there is a void in such case the universe cannot be?homogenous
 olbers paradox reviewif the universe only extends out so far then it connot also be homogenous
 if the galaxy is now 100 million yrs away receding at 200 km/s how long did it take to get so far away?15 billion yrs
 The Sun contains all but about _____ of the total mass of the Solar System.1/500th
 The universe, according to the best available scientific evidence, is approximately _____ years old.14 billion
 The age of the Solar System, according to the best available scientific evidence, is approximately _____ the age of the universe1/3rd
 The number of stars in the Solar System is1
 Homogenoussame (on average)on all locations
 If we assume that the universe is homogenous, then we imply that the universe_Looks the same any from any location
 Why is it that the sky is dark between the star?You should be able to see a star in every direction. More distant stars fill the sapces of the earer ones. Should be birght in every direction w/ no dark spots.
 Hubble Law- Recession Velocities (v) of distant galaxies are proportional to their distances (d). This is the Hubble Law: v=Hod; Constant= Ho- called the Hubble constant= 20km/s for each million LY of distant
 If your roommate calls you and says she is near columbus OH, Which is 180 miles away, and she is traveling at 60 mph, how long ago did she leave lex?Time=distance/rate--> 180/60 = 3 hours ago
 Suppose we had chosen a galaxy twice as far away, would the time estimate be the same?yes, since the Hubble law predicts twice the recession velocity. So the ration of distance/rate = the same
 The Hubble law describes what property of the universe?Velocity; V=HoD
 The hubble constant is about 20 km/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 LYs?200 km/s
 what info can astronomers infer about the universe from the Hubble Law?The age of the universe
 Big Bang Model-universe began at a fixed moment in time (time zero)-Matter, Space & time came into exsitence at time zero -universe initally very hot and dense with time it expanded and cooled-Big bang model describes how conditions changes in universe, beginning very shortly after time zero. -model makes predictions about nature of universe today.
 -4.5 Billion YearsSun becomes main sequence star, planets newly formed
 At the end of the main sequence phase of the sun's lifetime, the core will be mostly composed of__ and the envelope will be composed of__Helium, Hydrogen
 What nuclear reaction will occur in the core of the sun immediately after its main sequence lifetime is over?None
 Gravitational contraction always:1. results in higher tempreature 2. continues until an internal energy source is available: .a Therefore: in the core of a star there is either 1. gravitational contraction or energy release via fusion reactions
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