Chapter 13: Stellar Evolution<BLURT>

Chapter 13: Stellar Evolution

1. Which of the following sequences correctly describes the evolution of the Sun from young to old? A. white dwarf, red giant, main-sequence, protostar
B. red giant, main-sequence, white dwarf, protostar
C. protostar, red giant, main-sequence, white dwarf
D. protostar, main-sequence, red giant, white dwarf

2. What heats a protostar? A. The light from nearby stars.
B. Gravitational energy from infalling material.
C. Fusion of hydrogen into helium.
D. Energy from their magnetic fields.

3. Because protostars are surrounded by dust and gas, astronomers must observe them with A. radar.
B. ultraviolet telescopes.
C. infrared and radio telescopes.
D. gamma ray telescopes.

4. What is a T Tauri star? A. Any variable star.
B. A red giant with a peculiar spectrum.
C. Any star found in the constellation of Taurus.
D. A young star that exhibits variable light and outflowing gas.

5. A star becomes a main-sequence object when A. nuclear fuel in its core can supply enough energy to stop its collapse.
B. it collapses, and its envelope becomes degenerate.
C. it stops fusing nuclear fuel in its core and starts to expand.
D. it forms planets.

6. What determines how long a star stays on the main sequence? A. Its temperature and mass.
B. Its luminosity and radius.
C. Its mass and luminosity.
D. Its radius and mass.

7. A star moves off the main sequence when A. nuclear fuel in its core can supply enough energy to stop its collapse.
B. it collapses, and its envelope becomes degenerate.
C. it stops fusing nuclear fuel in its core and starts to expand.
D. it forms planets.

8. As a star like the sun evolves into a red giant, its core A. expands and cools.
B. contracts and heats.
C. expands and heats.
D. contracts and cools.

9. Why is it easier for a high-mass star than for a low-mass star to burn helium? A. A high-mass star's core is already very hot, so it only needs to compress its core a little to burn helium.
B. High-mass stars are already burning helium on the main sequence.
C. Low-mass stars have proportionately less helium than high-mass stars.
D. This statement is false. It is much harder for high-mass stars to burn helium.

10. What is meant by a pulsating star? A. A rotating neutron star that emits radio waves in a narrow beam.
B. A star whose luminosity changes as it swells and shrinks rhythmically.
C. A planetary nebula.
D. A star whose mass changes as it comes into contact with another star.

11. A planetary nebula is A. another term for the disk of gas around a young star.
B. the cloud from which protostars form.
C. a shell of gas ejected from a star late in its life.
D. what is left when a white dwarf star explodes as a supernova.

12. What is left when a planetary nebula dissipates? A. A red giant.
B. A black hole.
C. A white dwarf.
D. A neutron star.

13. Stars like the Sun probably do not form iron cores during their evolution because A. all the iron is ejected when they become planetary nebulas.
B. their cores never get hot enough for them to make iron by nucleosynthesis.
C. the iron they make by nucleosynthesis is all fused into uranium.
D. their strong magnetic fields keep their iron in their atmospheres.

14. What makes a high-mass star's core collapse? A. Energy from its outer layers compresses its core.
B. The only thing that can make a star's core collapse is a collision with another star.
C. Massive stars have iron cores. Iron cannot burn and release energy, so nuclear fusion stops and the core collapses.
D. Massive stars' cores don't collapse. They expand and become planetary nebulas.

15. What kind of subatomic particles have been observed when a supernova explodes? A. Neutrinos.
B. Electrons.
C. Protons.
D. Positrons.

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