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Exam3_f16_review_solutions - Fall 2016 Astronomy 1 Review...

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Fall 2016Astronomy 1 – Review Topics for Exam 3Sun- What is nuclear fusion? Why do the nuclear fusion reactions in the Sun produce energy?- Write out the nuclear fusion reaction occurring in the core of the Sun right now.- What are the different layers within the Sun?- What part of the Sun do we see?- What is the surface temperature of the Sun?- What are sunspots and why do they appear? How long is the cycle of sunspots?Properties of Stars- What is a brown dwarf? - What prevents a brown dwarf from undergoing nuclear fusion?
- What are the minimum and maximum masses of stars?Explain why there is a minimum and a
- Why are binary stars useful?For finding masses of stars – can use Newton’s version of Kepler’s law.
- What is a typical composition of stars?74% H, 25% He, and about 1% metals.
- What prevents a brown dwarf from undergoing nuclear fusion?Electron degeneracy pressure; browndwarfs are not massive enough to over come the degeneracy.
- What is the determinant stellar property in Spectral classification: OBAFGKM?Temperature- Why do O stars have weak Hydrogen absorption lines?Most H is ionized since these stars are really hot
- Why do M stars have so many absorption lines?They are cool enough for molecular bonds to be intact
so molecules produce a lot of absorption lines in these stars.- Which type of stars are most common? Least common?Most common – low mass stars, least common– high mass stars.
- H-R diagram: know how to draw it; be able to draw the different groups of stars on it (Main Sequence,Red Giants, Supergiants, White dwarfs); what type of star is the Sun, where is it on the diagram…- Where are the more massive stars on the Main sequence?- Where are larger stars? Hotter? More luminous?- Explain each stage of evolution of the Sun from now until it becomes a white dwarf.Be able to drawan
H-R diagram for the evolution of 1 Msun star. Label each evolutionary phase and state (or sketch) whichfusion reactions occur in the core and in the shell around the core. Explain what happens at each stage(e.g. the core shrinks, which increases its temperature, which...).Which stage last longest?
Fall 20167 – 8 = subgiant* no fusion in core, H -> He in the shell which causes the outer layers of star to expand8 – 9 = red giant* no fusion in core, H -> He in the shell, He builds up (mass of He increases) and gravityincreases, shrinking the core further and heating it up.Thermal pressure in the core is too small to

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Term
Spring
Professor
MILLER,DAVIDEMAN
Tags
Astronomy, Astronomical, Black Holes, Black hole, White dwarf, degeneracy pressure

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