Questions and Answers
What details might we observe on the surface of a G-type star?
Sun spots
Compare an O-type main sequence star with a K-type main sequence star.
O-type: Blue color, 25,000K temp; K-type: Orange to Red color, 3,500-5,000K temp.
What is the Mass-Luminosity relationship for main sequence stars?
The greater the mass of a main sequence star, the brighter it is.
Which main sequence stars are the bluest? The reddest?
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What is the approximate surface temperature of a G0 type star?
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What are the elements and stages of pre-main-sequence stellar evolution?
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How are Type I Supernovae produced? Type II?
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Where were the Carbon, Nitrogen, and Oxygen atoms in your body created?
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What are the stages of evolution of very massive stars?
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What are the end-states of low-mass star evolution? Of high-mass star evolution?
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What causes the luminosity of a star?
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What is hydrostatic equilibrium?
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Which stars evolve the most rapidly?
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What condition keeps a white dwarf from collapsing further?
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What defines a star on the main sequence?
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Where are elements heavier than Iron created?
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What is a pulsar?
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What is a planetary nebula?
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What stellar property determines the final stages of a star's life?
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What is a white dwarf?
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How can we measure a star's surface temperature?
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Study Notes
G-Type Stars
- Surface features include sunspots, which are cooler and darker areas caused by magnetic activity.
Comparison of Main Sequence Stars
- O-type stars: Blue, temperature around 25,000K, characterized by singly ionized helium lines and strong ultraviolet emissions.
- K-type stars: Orange to red, with temperatures between 3,500-5,000K, dominated by metallic lines and weak blue continuum.
Mass-Luminosity Relationship
- Higher mass in main sequence stars correlates with increased brightness.
Color of Main Sequence Stars
- Bluest stars: O, B, and A types.
- Reddest stars: K and M types.
G0 Type Stars
- Approximate surface temperature ranges from 5,000 to 6,000K.
Pre-Main-Sequence Stellar Evolution
- Stages include protostar, main-sequence star, planetary nebula, and white dwarf.
Supernova Types
- Type I: Occurs when a star accrues matter from a companion, leading to a runaway nuclear reaction.
- Type II: Results from a star exhausting its nuclear fuel and collapsing under gravity.
Element Formation
- Carbon, nitrogen, oxygen, and calcium atoms are formed through nuclear fusion in stars, later dispersed by supernovae.
Evolution of Very Massive Stars
- Progression: Protostar → Main Sequence → Subgiant → Red Giant → Asymptotic Giant Branch (AGB) → Supernova → Black Hole or Neutron Star.
End-States of Star Evolution
- Low-mass stars evolve to a horizontal branch with a helium burning core, progressing through a red giant phase and ending as a white dwarf.
- High-mass stars undergo similar stages but with additional nucleosynthesis creating heavier elements before collapsing.
Luminosity Source
- Stars gain luminosity primarily through nuclear fusion processes.
Hydrostatic Equilibrium
- A balance between gravitational force and internal gas pressure maintains stability within a star.
Stellar Evolution Rate
- The most massive stars evolve at the fastest rates.
White Dwarf Stability
- Degeneracy pressure prevents further collapse of a white dwarf.
Main Sequence Definition
- Main sequence stars actively fuse hydrogen into helium in their cores.
Formation of Heavier Elements
- Elements heavier than iron are primarily produced during supernova events.
Pulsars
- Pulsars are rapidly spinning neutron stars, emitting low-frequency radio waves after a supernova explosion.
Planetary Nebula
- A planetary nebula consists of gas expelled from a low-mass star nearing the end of its life, often showing a bipolar shape.
Final Stages Determined by Mass
- The mass of the star is a critical factor in determining its final evolutionary stages.
White Dwarf Characteristics
- A white dwarf is a dense remnant of a low-mass star, roughly planetary sized, that results from the loss of outer layers after nuclear fuel depletion.
Measuring Surface Temperature
- Surface temperature can be gauged by analyzing a star's color using filters at different wavelengths to compare light intensity.
Star Formation
- Stars originate from dense regions within molecular clouds in space.
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Description
Prepare for your ASTR Exam 2 with these flashcards covering key concepts such as G-type and O-type stars. Each card presents essential details to help you understand stellar characteristics and comparisons. Test your knowledge on the different types of main sequence stars and other important astronomical phenomena.
