Download Astronomy Learning Objectives and Study Questions for Chapter 12

Astronomy
Learning Objectives and Study Questions for Chapter 12
1. Briefly describe the "milestones" that separate protostars from pre-main-sequence
stars, and pre-main-sequence stars from main-sequence stars.
2. Briefly describe how a reflection nebula differs from an emission nebula in origin
and appearance.
3. Estimate the main-sequence lifetime of a star with a known luminosity relative to
the Sun.
4. Briefly describe how the behavior of degenerate He differs from "normal" He when it
is heated, and what role this difference plays in leading to the sudden onset of Hefusion ("helium flash") in the core of a fairly low-mass star.
5. Estimate the relative ages of two star clusters by comparing the main-sequence
turnoffs of the fields they define on an H-R diagram.
6. Determine the absolute magnitude of a Type I or II Cepheid from its pulsation period
(given an appropriate graph) and combine this with its apparent magnitude and the
distance-magnitude equation to determine how far it is from Earth.
7. Briefly describe the conditions necessary for mass transfer to occur in a binary star
system.
1. Prototstars become pre-main-sequence stars when they _____.
A. begin to heat up
B. stop accreting gas
C. begin fusion in their cores
D. reach the main sequence
E. exhaust H in their cores
2. When the core of a pre-main-sequence star becomes hot and dense enough for
fusion to begin, the star is termed a _____.
A. Bok globule
B. brown dwarf
C. main-sequence star
D. OB association
E. emission nebula
3. Paradoxically, stars with the highest initial masses are the _____.
A. farthest away
B. nearest
C. dimmest
D. coolest
E. first to move off the main sequence
4. Small stars with masses of 0.08-0.4 M that convect internally and convert all their H
to He over hundreds of billions of years are _____.
A. protostars
B. brown dwarfs
C. red dwarfs
D. T-Tauri stars
E. white dwarfs
5. At the end of its main-sequence life, H-fusion in a medium mass star like Sol will shift
to a shell outside the core and the star will become a _____.
A. red dwarf
B. red giant
C. white dwarf
D. blue-white supergiant
E. supernova
6. The period during which an RR Lyrae or Cepheid variable star brightens and dims is
directly related to its _____.
A. distance
B. temperature
C. composition
D. apparent magnitude
E. absolute magnitude
7. Star clusters are important for understanding stellar evolution because the stars in
them are similar in most respects, except _____.
A. ages
B. distances from Earth
C. masses
D. initial compositions
E. they are similar in all these respects
8. Which of the star clusters plotted on the accompanying
H-R diagram, α or β, is older?
A. α
B. β
C. both are the same age
D. depends on observer’s location
E. indeterminate, cannot tell from the data given
9. In a binary star system, mass can flow from one
companion to the other if either _____.
A. is a giant
B. becomes a supernova
C. fills its Roche lobe
D. has a H-rich atmosphere
E. is detached
10. Unlike normal He, the “degenerate” He in Sol’s core at the end of its main-sequence
life will not _____.
A. cool by expansion
B. heat up
C. fuse into heavier elements
D. occupy any space
E. exert a gravitational pull
11. In giants with masses greater than 2 M, no He flash occurs, and He fusion proceeds
smoothly to produce _____.
A. silicon and oxygen
B. silicon and iron
C. oxygen and iron
D. carbon and oxygen
E. carbon and silicon
12. Young population I stars, like Sol, are rich in _____ compared to older population II
stars.
A. H
B. He
C. “metals”
D. numbers of planets
E. attitude