Questions and Answers
Which list of spectral types is in order of decreasing strength of their hydrogen lines?
What is the order of spectral types starting from the strongest property?
C, B, D, E, F, G, A
Redder main-sequence stars are fainter on average than bluer main-sequence stars.
True
What property of a star determines its color?
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What properties would increase if the mass of a main-sequence star is increased?
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What property can we use to further classify stars aside from temperature?
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Rank the luminosity classes in order of increasing size.
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What is the complete classification of the Sun?
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Where might a K5 I star and a K5 V star be located on the H-R diagram?
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A K5 I star has a larger radius than a K5 V star.
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Study Notes
Spectral Types and Absorption Lines
- Stars are grouped into spectral types to understand their differences.
- Spectral classification is based on the strength of hydrogen absorption lines.
- In order of decreasing strength: A0, B0, F0, G0, K0.
Physical Properties of Stars
- The classification of stars has evolved to consider physical properties beyond hydrogen absorption.
- A more meaningful order of stars based on specific properties can be established from data.
Hertzsprung-Russell Diagram
- Hertzsprung and Russell plotted stellar luminosities against spectral types.
- H-R diagram shows a pattern with spectral types OBAFGKM.
- Main-sequence stars exhibit the trend that redder stars are generally fainter than bluer ones.
- Spectral type dictates the star's color.
Star Temperature and Color
- The temperature of a star is the fundamental property that determines its color and spectral type.
- Stars emit light akin to blackbodies, leading to specific spectral characteristics.
Main-Sequence Stars
- The Sun and most stars lie along the main sequence of the H-R diagram.
- Increasing a main-sequence star's mass results in higher temperature, luminosity, and radius.
Classification and Luminosity
- Spectral type correlates with temperature; luminosity also depends on size.
- Stars can be further classified with their radius to help refine their position on the H-R diagram.
Luminosity Classes
- A star's classification requires its spectral type and luminosity class.
- Luminosity classes are designated by Roman numerals I (largest) to V (smallest), plus white dwarfs (WD).
Sun's Classification
- The Sun is classified as G2 V, indicating its spectral type and luminosity class.
Positioning on the H-R Diagram
- K5 I stars are located higher on the H-R diagram compared to K5 V stars due to their larger radius.
Stellar Properties
- A K5 I star has a larger radius than a K5 V star, emphasizing the distinction in luminosity classes.
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Description
Test your knowledge on spectral types and their significance in classifying stars. This set of flashcards covers essential concepts related to main-sequence stars and their hydrogen absorption lines. Perfect for reviewing before your final exam in Astronomy 1010.
