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- Q1 At what wavelength does the spectrum of a 10000 K type A star
peak?
Use Wien’s Law: λ = 3000000 nm/T, so 300 nm.
- Q2 Fusion of very light elements to make heavier ones releases energy,
as does fission of very heavy elements to make lighter ones. The most
"energetically favorable" and stable element from which
neither fission nor fusion can release energy is IRON
- Q3 Sunspot brightness, use E = σT4
- (T1/T2)4 = (5800/4200)4 = 3.6 times brighter
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2
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- Q4. d =145 pc, M = -5.2, use m – M = -5 + 5log(d/1pc), so m = 0.6 (other
answers bad)
- Q5. Sirius: m=-1.5, M=1.4.
Recall 10 pc is about 30 lt. yrs, and M = m at 10 pc. m < M, so Sirius must be
closer than 10 pc!
- Hard method: m – M = -5 + 5log(d/1pc), so less than 30 years
- Q6: Binary system SS Cygni: use
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3
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- Q9. 6. Same M, one star is type G, one is type B. G is bigger
- Q10. Star cools by factor of
2, expands by factor of 10, what is its new luminosity compared to
old? L goes as R2T4
so the temperature change reduces L by 16 times, and the expansion
increases it by 100 times, and 100/16 = 6.25.
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Notes