ASTR 105 Lecture Notes - Lecture 10: Red-Giant Branch, Asymptotic Giant Branch, Density Wave Theory
Lab AST 105 Lecture Notes 10:
• How are stars created
• Clouds of dust/gas collapse creating a dense, hot core which begins gathering dust and
gas.
• Which five type of events can trigger the formation of stars and their planets
• A spiral density wave, Collisions, Tidal Influences, Ionization patterns, & a heavy short-
lives star dies
• What is the first stage of star formation after the initial trigger
• The cloud of gas/dust fragments as it collapses until pieces collapse to become individual
stars
• What happens when a cloud fragment contracts
• its internal motions are enhanced
• What are the three types of internal motions
• Faster turbulence in the cloud/ Faster-moving atoms in cloud/ Faster rotation of the
cloud, and faster notation of the fragments
• While collapsing happens the outer looser portions flatten to become a
• Disk
• What is a Protostar
• the center portion of the collapsing gases that are becoming a star system
• When does Nuclear Fusion happen in protostar's
• When the pressure of the collapsing dust is too much that it causes the core to become
hot enough for nuclear fusion
• When do Protostars stop collapsing
• When Nuclear Fusion occurs
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• Once the a star is created where does it fall on the H-R Diagram
• The Main Sequence
• What are Brown Dwarfs
• Failed stars, because they are too light weight and nuclear fusion doesn't occur
• What are the competing forces that are equal when the star maintains a constant size
• Pressure and the outflow of energy produced by the star competing against the inward
force of gravity
• Why are outer portions of most stars never burnt
• Because gas there never seeps deeply enough to get to the super-hot core
• When does a star leave the Main-Sequence
• When a star runs out of hydrogen to burn
• When does a star become a Red Giant
• when the star expands and it's surface cools and/or reddens
• What happens to a star when it runs out of helium to burn
• The star core energy flow decreases, outward please decreases, weight of star crushes
inward, inner core & outer core shrink, this causes the star to panic and the core
increases and the star expands burning fuel faster than before
• Is the surface temperature of a regular star hotter than a Red Giant
• Yes
• What are the stages that come later in a star's life
• Subgiant( Star expands and turns orange), red giant branch( Star continues to expand
turns red), horizontal branch(stage after helium flash and burns helium), and asymptotic
giant branch(Expand and surface temperature cools)
• When something contracts it heats up and spins....
• Faster
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• When something expands and cools it spins...
• Slower
• What are the only two ways dust can be made
• Through supernova death of stars & red giant stars
• What is a helium flash
• Event that occurs when temperature hits 100 million K, hot enough to begin helium
fusion
• What event is the end mark of the red giant phase
• Helium Flash
• After helium flash, stars mainly burn helium to make what kind of atoms
• Carbon and some Oxygen
• What happens to Sun sized stars when they die
• They pulsate multiple times until it loses its outer layers and becomes a planetary
nebula, the core becomes a white dwarf
• What is the average size of a White dwarf
• Around the size of planet Earth
• What is the cause of a "nova"
• Explosion of a star
• How often can a "nova" occur
• Multiple times for the same white dwarf
• How often can a "supernova" occur
• Only once, object is completely destroyed
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