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PHYS 190 Study Guide - Final Guide: Solar Mass, Oneword, PhotonExam

Course Code
PHYS 190
Howard Trottier
Study Guide

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MC for Final:
1. The Hubble Space Telescope obtains higher-resolution images than most major ground-based
telescopes because
- It is above Earth’s atmosphere
2. Consider the blue-white star Vega. Assuming that it is a main sequence star, what could we infer
about it from its colour?
- (It is much more massive than the Sun, It is much more luminous than the Sun, Its surface is hotter than
our Sun, All of the listed answers are correct)
3. What do we mean when we say that the Sun is in gravitational equilibrium?
- There is a balance within the Sun between the outward push of gas pressure, and the inwards
compression due its own gravity.
4. In the diagram, in which case will the observer see a continuous spectrum? (22,23,24
- (1)
5. In the diagram, in which case will the observer see a spectrum that is almost entirely black, except
for a few bright emission lines?
- (3)
6. In the diagram, in which case will the observer see a continuous spectrum interrupted by a few dark
absorption lines?
- (2)
7. In the diagram, which star emits more red light?
- (A)
8. In the diagram, which star looks redder?
- (B)

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9. Which of these is emitted when an electron falls from a higher atomic orbital to a lower one?
- a photon
10. Since the Sun radiates most strongly at a wavelength of about 500 nm, a star with twice the surface
temperature would radiate most strongly at about
- 250nm
11. What happens when the solar nebula contracts?
- It heats up, It flattens out, It spins faster; all of the above
12. What natural barrier must two protons overcome in order to collide and fuse?
- electromagnetic repulsion, also known as the Coulomb barrier
13. In the proton-proton cycle, the produced particles, including the helium nucleus, have less total mass
than the total mass of the hydrogen nuclei consumed in the reaction. What happens to the "lost"
- It is converted to energy.
14. If the centre of the Sun could be heated slightly, the rate of nuclear reactions would increase, and
the core would
- expand and cool until it returned to equilibrium
15. A star with a parallax of 0.01 arcseconds is at a distance of
- 100 parsecs. There is an inverse relation between star's parallax and its distance. A star which has a
parallax 1 arcseconds is at a distance of 1 parsec, which is equal to 3.26 light years. Hence a star which
has a parallax of 0.01 arcseconds, will be at a distance of 10.01 or 100 parsecs or 326 light years.
16. The critical temperature to initiate the proton-proton cycle in the cores of stars is (choose the closest
- 10 million K
17. Since all stars begin their lives with the same basic composition, what characteristic most
determines how they will differ?
- mass they are formed with
18. In the HR diagram above, which group represents stars that are hot but dim?

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- (b)
19. In the HR diagram above, which group contains white dwarfs?
- (b)
20. In the HR diagram above, which group has stars that are burning only hydrogen in their cores?
21. In the HR diagram above, which group has the most massive stable stars?
22. Distance determinations using spectroscopic parallax assume that
- the star is on the main sequence
23. A star is on the horizontal branch of the H-R diagram. Which statement is true?
- It is stably burning both hydrogen and helium
24. Carbon fusion does not occur in the lowest-mass stars because ...
- the cores of low-mass stars never get hot enough
25. What is a planetary nebula?
- Gas ejected from a low-mass star in the final stage of its life.
26. What forces a star like our Sun to evolve off the main sequence?
- It builds up a core of inert helium.
27. A star will spend most of its life:
- on the main sequence.
28. In a young star cluster, when the most massive stars are evolving into red giants, the least massive
stars are
- barely starting to fuse hydrogen
29. What can happen to the white dwarf in a close binary system when it accretes matter from the
companion giant star?
- It might blow off the material and brighten temporarily as a "nova", or, if enough material manages to
accrete, it can detonate as a type I supernova.
30. Which of these does not exist?
- a 1.5 solar mass white dwarf
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