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133 Cards in this Set

  • Front
  • Back
How are stars born?
in clouds of interstellar gas
Why do stars shine?
with energy produced by nuclear fusion in their cores
How do stars die?
when they finally exhaust all sources of fuel for fusion
How is a star born?
When gravity causes a cloud of interstellar gas to contract to the point at which the central object becomes hot enough to sustain nuclear fusion in its core.
What might cause gravity not to succeed in making an interstellar cloud contract?
The cloud's internal gas pressure can resist gravity
What is the term for the balance of the inward pull of gravity by the outward push of gas pressure?
Gravitational equilibrium
T or F
In most places with our galaxy gravity is not strong enough to overcome the internal pressure of interstellar gas.
True
List the 2 things that help gravity win out over pressure to start the collapse of a cloud of gas:
1. higher density in the gas cloud helps because packing the gas particles closer together makes the gravitational forces between them stronger;
2. lower temperature in the gas cloud helps gravity because lowering a cloud's temperature reduces the gas pressure.
T or F
Star-forming clouds are warmer and less dense than most other interstellar gas.
False,
Star-forming clouds are colder and denser than most other interstellar gas.
What is the name for the clouds of interstellar gas that form stars?
Molecular clouds
Why are star forming interstellar clouds of gas called molecular clouds?
their low temperatures allow hydrogen atoms to pair up to form hydrogen molecules
What does 0 K =
absolute zero
What are the average temperatures around Earth?
300 K
What is the avg temperature of the star-forming clouds of interstellar gas?
10-30 K
T or F
Molecular clouds that give birth to stars tend to be small.
False,
Molecular clouds that give birth to stars tend to be large
T or F
Molecular clouds can give birth to many stars at the same time.
True
T or F
Stars are generally born in clusters.
True
What is the term for the dense center of a collapsing molecular cloud fragment, or
What is the term for the clump of gas that will become a new star?
Protostar
How do protostars rotate when they form?
Rapidly
AS the cloud contracts, how does the it rotate?
Faster
T or F
Protostars are not yet true stars.
True
What is shape formed by the shrinking molecular cloud fragment?
A spinning disk
Why does a shrinking molecular cloud fragment form a disk?
As the protostar rotates faster , collisions between gas particles tend to flatten the gas
What is the term for the violent, high speed streams of gas that is released during the last stages of a star's formation?
Jets
How many jets and in what direction are they firing are usually seen during the last stages of a star's formation?
2 jets are usually seen, shooting in opposite directions along the protostar's rotation axis
What helps the protostar generate a strong protostellar wind?
The protostar's strong magnetic field
What is the term for the outward flow from the protostar of particles similar to the solar wind, but is much stronger?
Protostar wind
What is the term used when 2 stars end up quite close to each other and start rotating each other?
Close Binary system
When does a protostar become a true star?
When its core temperature reaches 10,000,000 K.
What halts the protostar's gravitational contraction?
Ignition of fusion
What influences the length of time from the formation of a protostar to the birth of a main-sequence star?
The star's mass
What size stars act with quicker speed, large or small
Large
T or F
The most massive stars in a young star cluster may live and die before the smallest stars even begin to fuse hydrogen in their centers.
True
T or F
Stars with low masses greatly outnumber stars with high masses.
True
What is the observed maximum mass of a star?
150M
Sun
What is the minimum mass a protostar needs to become a star?
0.08M
Sun
What is the term for a "failed star", a star whose mass is insufficient to sustain steady fusion?
Brown dwarf
What interstellar objects occupy a fuzzy gap between what we call stars and planets?
Brown dwarf
What is the term for ordinary gas pressure?
Thermal pressure
T or F
Raising the temperature raises the particle speeds and thereby raises the thermal pressure.
True
T or F
Thermal pressure is insufficient to fend off gravity in a brown dwarf.
True
What cause the crush of gravity in a brown dwarf?
Degeneracy pressure
What is the term for a type of pressure that does not depend on temperature but on the laws of quantum mechanics?
Degeneracy pressure
How do quantum mechanics effect a brown dwarf?
The electrons become packed closely enough, but because their cores are so small, not all of the electrons can squeeze in and therefore gravity never can continue to cause the brown dwarf to contract.
What is a star's most important property?
Its mass
In relation to our Sun, how big are low mass stars?
less than 2X as big
How long has our Sun been shining as a main-sequence star?
5 billion years
How does our Sun fuse hydrogen?
Proton-proton chain
Why does the Sun shine steadily?
The self regulating process, solar thermostat, which is the gravitational equilibrium and the balance between the core energy production rate and the rate which energy escapes into space.
What percent of a star's lifetime is spent nuclear burning?
90%
What supplies the thermal energy that maintains the Sun's internal pressure and holds gravity at bay?
Hydrogen fusion
How much longer will it take for our Sun to reach another stage?
5 billion more years
After burning for 10,000,000,000 years,10 billion years, what stage will our Sun become?
Red Giant
How long will it take for the Sun to grow in size and luminosity to become a red giant?
1 billion years
At the peak of its red giant stage, how big will our Sun be?
100X larger in radius and
1000X brighter in luminosity
What will cause our Sun to grow in size into its red giant stage?
The Sun's outer layers will expand outward when the nuclear fusion ceases and gravitational pull.
And the core will not longer be able to resist the inward pull of gravity.
What is the term for the action of the hydrogen fusion in a shell around the core
Hydrogen shell burning
T or F
Winds from red giants show that they carry away much more matter than the solar wind carries away from the Sun today.
True
What will happen when there is a rise in the fusion rate of the Sun?
It cause the core to inflate and cool until the fusion rate drops back down.
What is the term for a type of degenerating star whose low-mass causes it's inert helium core never to become hot enough to fuse helium and the core collapse is halted by degeneracy pressure?
Helium white dwarf
T or F
The helium nuclei has a greater charge than a hydrogen nucleus.
True
T or F
Helium fusion requires much high temperatures than those needed for hydrogen fusion.
True
What is another term for helium fusion?
Triple-alpha reaction
What is another term for helium nuclei?
alpha particles
What happens in helium fusion?
3 helium nuclei are converted into 1 carbon nucleus
What is a byproduct of triple alpha reaction?
Energy because the mass of the carbon nucleus is slightly less than that of the 3 helium nuclei.
T or F
Degeneracy pressure does not increase with temperature.
True
How fast does the core heat up by helium fusion?
Rapidly
What is the term for the rapid increase in helium fusion rate caused by rising temperature rates?
Helium flash
The longer a star undergoes hydrogen shell burning, the ________ and _________ luminous it becomes.
The longer a star undergoes hydrogen shell burning , the larger and more luminous it becomes.
What is the term for stars that have just begun their expansion into red giants as their cores have shut down and hydrogen shell burning has begun?
Subgiants
Where on the H-R diagram are the helium-burning stars that already undergone the helium flash and become helium-burning stars?
They trace out a horizontal line known as the horizontal branch
When will the Sun's helium-burning shell run out?
After it has burned 100 million years
AFter the helium-burning shell has ceased burning, what happens to the core?
The carbon "ash" from helium fusion, will begin to shrink once again under the crush of gravity.
What will happen to the size of the Sun after the core helium is exhausted?
The Sun will expand once, again.
What will be the trigger for the Sun's expansion after the core's helium-burning has exhausted?
Helium fusion in a shell around the inert carbon core.
What is the term given to the stage of a red giant when the shell around the inert carbon has helium fusion occurring along with the hydrogen shell is still burning atop the heliumlayer?
Double-shell burning star
What happens to the temperature and size of the Sun when, as a red giant, it s a double shell burning star?
The temperature rises causing the Sun to expand and increases the luminosity to more than it was in the first red giant stage.
Why do temperature, size and amount of luminosity increase when the Sun is a double shell burning star?
Both shells will contact along with the inert core
How long does the Sun last as a double shell burning star?
A few million years at most.
When is carbon fusion possible?
At temperatures above
600 million K.
What prevents the Sun's temperature from reaching 600 million K at this stage?
Degeneracy pressure.
As the Sun's radius and luminosity rise, what happens to its stellar winds?
The stellar winds grow stronger
What do the stellar winds provide as a product of the dying star?
Interstellar dust grains
How do interstellar dust grains form?
Because the wind cools as it flow away from the star.
What causes the dying star's to glow brightly?
The radiation emitted from the exposed core will ionize the gas in the expanding shell.
What is the term for the brightly glowing core that has been exposed as the dying star has ejected its outer layers into space?
Planetary nebula
T or F
Planetary nebula are related to planets.
FALSE!!!
Planetary nebula have NOTHING to do with planets.
What is the appearance of planetary nebulae?
They look much like planets through small telescopes, appearing as simple disks.
What is the term for the leftover carbon core of a dying star?
White dwarf
White dwarfs are ________ in radius but _______ in mass.
White dwarfs are small in radius but high in mass.
What will be the effect on Earth when the Sun begins to increase its luminosity as it enters the red giant stage?
It will cause a runaway greenhouse effect.
What will happen to the Earth when it experiences the runaway greenhouse effect?
Make the Earth's oceans boil
How long will it take for the Earth to start experiencing the runaway greenhouse effect as the Sun ?
In about 1-4 billion years from now
Just before the Sun experiences its helium flash, how luminous will the Sun be?
1,000 X more than it is now.
What location in our solar system will have their surface temperatures rise to abaout the present temperature of Earth?
Saturn's moon Titan
What is the term for the plotting of a star's stages of life on an H-R diagram?
Life track or Evolutionary track
Which type of stars, low or high mass, produce the full array of elements on which life depends?
High mass stars
From what type of star, low-mass or high-mass, do supernova result?
High-mass stars
What is the term for the titanic implosion of a high-mass star when it finally exhausts all increasing heavy fusions?
Supernova
What is the term for the chain reaction that occurs in the hydrogen fusion high-mass stars?
CNO cycle or

Carbon, Nitrogen, Oxygen cycle
How many steps are there in the CNO cycle?
6
What is the result of the 6 steps of the CNO cycle of a high-mass star:
4 Hydrogen nuclei fuse to form 1 helium nuclei
T or F
Carbon, nitrogen, and oxygen nuclei help the CNO cycle to proceed, but these nuclei are neither consumed nor created in the overall cycle.
True
What is the name of the closest red supergiant stars to the Earth?
Betelgeuse (pronounced beetlejuice)
How large is Betelgeuse (pronounced beetlejuice)
500 solar radii, or more than 2X the distance between the Sun and Earth
T or F
We do not know what stage nuclear burning Betelguese is at.
True
Why can't low-mass star make elements heavier than carbon?
Degeneracy pressure halts the contraction of its inert carbon core before it can get hot enough for fusion.
What causes a high-mass star to keep its carbon core so hot that degeneracy pressure never prevents it from reaching high temperatures?
The crush of gravity in the high-mass star
T or F
The nuclear reactions in a high-mass star's final stages of life are complex and many different reaction may take place simultaneously.
True
What is the term given to the simplest sequence of fusion stages that occurs during the final stages of a high-mass star's life?
Helium-capture reactions
What happens during helium-recapture reactions that occur during the final stages of a high-mass star?
A helium nucleus fuses into some other nucleus.
Name some elements that can be formed by helium recapture reactions?
Carbon can fuse together to form oxygen.
Oxygen can fuse together to form neon
Neon can fuse together to form magnesium
Etc., etc.
Why is iron unique as an element?
Iron is the one element that is impossible to generate any kind of nuclear energy
What are the 2 basic processes that can release nuclear energy
1. fusion
2. fission
Why does fusing hydrogen into helium generate energy?
Because helium has a lower mass per nuclear particle than the hydrogen nuclei.
The fusion of ______ nuclei into ________ nuclei generates energy until the trend reaches iron.
The fusion of light nuclei into heavier nuclei generates energy until the trend reaches iron.
At what point does the trend of the fusion of light nuclei into heavier nuclei reverse in nuclear fusion?
Beyond iron
How is it possible for elements heavier than iron to generate nuclear energy?
Fission of lighter elements
Why can't iron release energy by either fusion or fission?
Because iron has the lowest mass per nuclear particle of all nuclei.
What happens when the matter in a stellar core turns to iron?
It cannot generate any further energy.
T or F
Older stars contain smaller amounts of heavy elements than younger stars.
True
T or F
Elements with even numbered protons in their nuclei outnumber those with odd numbers of protons
True
T or F
Elements heavier than iron are in abundance.
False,
Elements heavier than iron are extremely rare.
What is the term for the ball of neutrons that is left behind when a supernova occurs?
A neutron star
What happens when the remaining mass of a neutron star is so large that gravity also overcomes neutron degeneracy pressure?
The core continues to collapse until it becomes a black hole
What is the term for the expanding cloud of debris from a supernova explosion?
Supernova remnant
When was the last supernova seen in the Milky Way?
1604.
What is the Algol paradox?
The Algol binary system is tidally locked so that they alway show the same face to each other.
What is the term for the process of the gas exchange that can happen when gas from outer layers can spill over onto a companion star in a binary system?
Mass exchange
What is the Algol paradox?
Why is one of the stars larger than the other?
Describe the solution of the Algol paradox
The smaller, the subgiant was actually more massive, but as the more massive star, it was the first to begin expanding into a red giant.
As it expanded, so muc of its matter spilled over onto its companion that it is now the less massive star
T or F
Larger mass stars evolve more quickly than lessor mass stars.
True