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Ay123 Lecture I:Learning Outcomes
● Overview of how to measure the fundamental properties of stars● Mass● Radius● Temperature● Composition
● Stellar classification schemes● 5-minute overview of stellar evolution
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Parallax
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Spectroscopic binaries
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Eclipsing binary
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Spectral energy distributions of bright stars can be used to derive effective temperatures
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Ay123 Activity 1:Pick the larger star
BlustarusArcturus
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Ay123 Activity 1:Pick the larger star
Let’s pretend Michelson & Pease resolved both stars at ΔΘ = 0.04”.
BlustarusArcturus
0.04” 0.04”
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Ay123 Activity 1:Pick the larger star
Which star has the larger radius?a) Arcturusb) Blustarusc) They’re the same.d) not enough information
BlustarusArcturus
0.04” 0.04”
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Ay123 Activity 1:Pick the larger star
Which star is farther?a) Arcturusb) Blustarusc) They’re the same.d) not enough information
BlustarusArcturus
0.04” 0.04”
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Ay123 Activity 1:Pick the larger star
Which star is intrinsically more luminous?a) Arcturusb) Blustarusc) They’re the same.d) not enough information
BlustarusArcturus
0.04” 0.04”
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Ay123 Activity 1:Pick the larger star
Which star has a higher temperature?a) Arcturusb) Blustarusc) They’re the same.d) not enough information
BlustarusArcturus
0.04” 0.04”
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Ay123 Activity 1:Pick the larger star
Now pretend that the parallaxes are known.
BlustarusArcturus
0.04” 0.04”
π = 9 mas π = 6”
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Ay123 Activity 1:Pick the larger star
BlustarusArcturus
0.04” 0.04”
π = 9 mas π = 6”
Which star is farther?a) Arcturusb) Blustarusc) They’re the same.d) not enough information
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Ay123 Activity 1:Pick the larger star
BlustarusArcturus
0.04” 0.04”
π = 9 mas π = 6”
Which star has the larger radius?a) Arcturusb) Blustarusc) They’re the same.d) not enough information
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Ay123 Activity 1:Pick the larger star
BlustarusArcturus
0.04” 0.04”
π = 9 mas π = 6”
If both stars have the same apparent brightness, which star is intrinsically more luminous?a) Arcturusb) Blustarusc) They’re the same.d) not enough information
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Stellar Spectral Energy Distributions
Wavelength(Å)
flux
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Spectral Classification
Diagnostic spectral lines act as independent measures of temperature in stellar atmosphere provided surface gravity is known
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Stellar Spectra: Giants vs Dwarfs
G
K
Stars are a 2-D sequence!
Giants are slightly cooler than dwarfs of a similar spectral class with redder continua. This is because line strengths depend on Teff and g
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Luminosity Classes
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The evolution of a single star
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The evolution of a population of stars
Zero Age MS
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Ay123 Activity 1:Pick the larger star
BlustarusArcturus
0.04” 0.04”
π = 9 mas π = 6”
Which star is on the main sequence?a) Arcturusb) Blustarusc) Both
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Ay123 Lecture I:Learning Outcomes
● Overview of how to measure the fundamental properties of stars● Mass● Radius● Temperature● Composition
● Stellar classification schemes● 5-minute overview of stellar evolution
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GRATUITOUS PUPPY PHOTO
