Download Chapter 15 (Star Lives)

Chapter 15
Star Lives
1. A Hertzsprung-Russell diagram reveals the lives of stars because it shows stars that:
A. all have the same age.
B. all have the same mass.
C. all have the same chemical composition.
D. are at different stages of their lives.
2. In making a model of a star, an astronomer does NOT have to know or assume:
A. that the energy given off is produced in the interior.
B. the mass of the star.
C. the chemical composition of the star.
D. the distance to that star.
3. For a star like our sun, once fusion reactions in the main sequence phase stop, the star will next
become a:
A. white dwarf.
B. black dwarf.
C. red giant.
D. blue supergiant.
4. What observation leads us to the inference that stars evolve?
A. They have different spectral classes.
B. They have different luminosity classes.
C. They have different masses.
D. We can directly see them evolve.
5. Which of these is NOT a major difference between the evolution of a one and a five solar mass
star?
A. The more massive star has a shorter lifetime.
B. The more massive star fuses hydrogen by the CNO cycle on the main sequence.
C. The less massive star produces helium by fusing four hydrogens atoms in its core.
D. The more massive star may end its life in a supernova explosion.
6. In an evolving cluster, which stars become red giants first?
A. Stars with masses like the sun's.
B. Stars with sizes smaller than the sun's.
C. The most massive stars (upper main sequence).
D. The stars with the most heavy elements.
7. During the main-sequence phase of its life, a star fuses:
A. hydrogen to helium in its core.
B. hydrogen to helium in a shell.
C. helium to carbon in its core.
D. helium to carbon in a shell.
8. After a star's core runs out of fuel, how does the core get to a high enough temperature to ignite
the next stage of fusion reactions?
A. By chemical reactions.
B. By other fusion reactions.
C. By gravitational contraction.
D. None of these; the fusion reactions stop.
9. What is the heaviest element that the most massive stars can fuse in their cores during their
normal lives?
A. Helium.
B. Oxygen.
C. Iron.
D. Uranium.
10. What is the most important difference between the stars found in globular clusters and those in
open clusters?
A. Globular cluster stars have a greater mass.
B. Globular cluster stars have a younger age.
C. Globular cluster stars have a lower percentage of metals.
D. Globular cluster stars are bluer in color and so hotter.
11. Which of these is the MOST IMPORTANT indicator of how a star will evolve?
A. Radius (size).
B. Chemical composition.
C. Mass.
D. Surface temperature.
12. Red giant stars manufacture heavy elements not only in their cores but also in _______ shells.
These elements get into the interstellar medium by _______ .
A. helium-burning, strong stellar winds.
B. hydrogen-burning, strong stellar winds.
C. photospheric, strong stellar winds.
D. helium-burning, internal pulsations.
13. If a collapsing region of gas and dust does not produce enough energy in the core to ignite
nuclear fusion, it will become a:
A. WIMP (weakly interacting magnetic protostar).
B. proton star.
C. white dwarf.
D. brown dwarf.
14. Our Sun is now in an evolutionary stage that lies on the _______ of the H-R diagram.
A. Pre-main sequence.
B. main sequence
C. type I sequence
D. post-main sequence
15. The balance between _________ forces and __________ forces determines the size of a star.
A. radiation/gravitation
B. gravitation/magnetic
C. gravitation/electromagnetic
D. gravitation/convective
16. Significant amounts of energy are transported from the interiors of stars through the process of
___________. This concept is supported by observations of the _____________ appearance of our
Sun.
A. convection/smooth
B. conduction/granular
C. radiation/smooth
D. convection/granular
17. The main cause of the increased size (radius) of Stars as they evolve off of the main sequence is
due to:
A. decreased radiation pressure.
B. increased gravitational forces.
C. helium burning in the outer shell of the star.
D. core collapse.
18. If you observe higher proportions of heavier elements in the star:
A. it's a relatively old star.
B. it's a relatively new star.
C. it's a population II star.
D. it is about to go supernova.
19. The luminosities of stars are determined from:
A. the measured radiation flux and the distance to the star.
B. only their temperatures.
C. heliocentric parallax and density.
D. measuring the sizes of eclipsing binary systems.
20. Once you know about the H-R diagram, you can determine a star's luminosity if you:
A. know its “type” and measure its temperature.
B. know its distance and mass.
C. know its size and distance
D. know its size and that it has a binary companion.
21. What causes the temperature of a star to rise if the fusion reactions have stopped?
A. Gravitational contraction.
B. Laser irradiation.
C. Helium burning.
D. Hydroelectric power.
22. The simplest explanation of the Pauli Exclusion Principle states:
A. no two energy states can be in the same electron.
B. no two masses can be in the same state.
C. no two different elements can have the same number of protons.
D. no two electrons can be in the same energy state.
23. The helium flash occurs when the core collapses, the overall temperature rises, and:
A. helium begins to burn through the triple alpha process.
B. helium begins to burn through the double alpha process.
C. hydrogen begins to burn through the triple alpha process.
D. hydrogen burns to helium.
24. The Pleiades is a good example of:
A. an elliptical galaxy.
B. an older globular cluster.
C. a RR Lyrae star.
D. a young open star cluster.
25. In color, globular clusters are:
A. blue from hot, young stars.
B. yellow from aging, giant stars.
C. red from emission of hydrogen around them.
D. white from main sequence stars.
26.- 31. Match these elements with their role in stellar evolution:
A. Helium
B. Carbon
C. Iron
D. Gold
26. Formed in triple alpha process in red giant stars.
27. Chief product of main sequence stars, second most common element.
28. Three of these fuse together in the triple alpha process.
29. Last common heavy element, has most stably bound nucleus.
30. Formed only during seconds of supernova core collapse.
31. Formed by main sequence stars by fusing four protons together.
32. Acts as a catalyst in hydrogen fusion in cores of hotter stars.
ESSAYS
1. Explain in terms of its role in stellar evolution why iron is much more common than any other
heavy element.
2. With one exception, which are more common on the periodic table, odd or even numbered
elements? Relate this to the red giant stage of stellar evolution.
3. If practically every star must eventually swell into a red giant, why are there only a handful of
them visible to the naked eye, compared to thousands of main sequence stars?
4. The Ring Nebula in Lyra is quite symmetrical, and the Crab Nebula of Taurus appears very
chaotic. Relate both to the end stages of red giants of differing masses.
S. We are all the children of stars that died so we could live. In what sense is this statement true, in
terms of stellar evolution?