Download Test 3, February 7, 2007 - Brock physics

Brock University
Number of pages: 8
Number of Students: 500
Number of hours: 50 min
Instructor: B.Mitrović
Test 3, February 2007
Course: ASTR 1F00
Date of Examination: February 7, 2007
Time of Examination: 8:00–8:50
1. The blue colour of a nebula arises because
(a) hot hydrogen in the nebula emits blue light.
(b) the red light is scattered away out of its path by gas and dust in the nebula.
(c) the blue light is absorbed by the gas and dust in the nebula.
(d) the blue light is scattered most efficiently by gas and dust in the nebula.
2. A reddish nebula is called
nebula.
(a) reflection
(b) planetary
(c) emission
(d) [None of the above.]
3. The density of a typical interstellar cloud is
the density of air at sea level.
(a) much smaller than
(b) much larger than
(c) about the same as
4. A bluish nebula is called
nebula.
(a) reflection
(b) planetary
(c) emission
(d) [None of the above.]
5. The red colour of a nebula arises because
(a) hot hydrogen in the nebular emits red light.
(b) the nebula surrounds a cool M-class star.
(c) the red light is scattered more than the blue light by gas and dust.
(d) [None of the above.]
6. In a spiral galaxy the interstellar material is least dense in the spiral arms of the galaxy.
(a) True.
(b) False.
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Course: ASTR1F00
Date: February 7, 2007
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7. A dark nebula appears dark because in reality it is empty space.
(a) True.
(b) False.
8. The more massive the star, the more time it spends in protostar stage.
(a) True.
(b) False.
9. The new stars are formed in the giant molecular clouds.
(a) True.
(b) False.
10. During the protostar stage, a star derives its energy from
(a) fusion of silicon into iron.
(b) gravitational contraction.
(c) fusion of hydrogen into helium via proton-proton chain.
(d) fusion of hydrogen into helium via CNO cycle.
11. The giant molecular clouds contain mostly
(a) ethyl alcohol.
(b) molecular hydrogen.
(c) ammonia.
(d) carbon monoxide.
12. Stars like the Sun do not form iron cores during their evolution because
(a) their cores are too hot to form heavy iron by nucleosynthesis.
(b) their cores never get hot enough for them to make iron by nucleosynthesis.
(c) their strong magnetic fields keep their iron in their atmospheres.
(d) all the iron is ejected when they become planetary nebulae.
13. Which of the following sequences describes the evolution of the Sun from young to old?
(a) Protostar, main-sequence, yellow giant, red giant, black hole.
(b) Protostar, main-sequence, yellow giant, red giant, neutron star.
(c) Protostar, main-sequence, red giant, yellow giant, red giant, white dwarf.
(d) [None of the above.]
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Course: ASTR1F00
Date: February 7, 2007
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14. The nonfusing dead core of a star is supported against its collapse by
(a) radiation pressure.
(b) degenerate electrons.
(c) its magnetic field.
(d) its own gravity.
15. The main-sequence stage of the Sun is estimated to be
long.
(a) 10 million years
(b) 10 billion years
(c) 1 billion years
(d) 100 million years
16. Once the hydrogen in the Sun’s core is fused into helium, further fusion of hydrogen into
helium will go on in
(a) its atmosphere.
(b) photosphere.
(c) a shell surrounding the helium core.
17. When a low-mass main-sequence star exhausts its core hydrogen fuel supply:
(a) the entire star shrinks in size.
(b) the core shrinks while the rest of the star expands.
(c) the core immediately begins to fuse its helium into carbon.
(d) the star becomes a neutron star.
18. The beginning of helium burning into carbon in the Sun’s core is called
(a) bipolar flow.
(b) helium pump.
(c) helium flare.
(d) helium flash.
19. Planetary nebula is
(a) a supernova remnant.
(b) a nebula in which planets form around a star.
(c) a glowing shell of material ejected by a dying low mass star.
(d) [None of the above.]
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20. If the mass of an object composed of degenerate material increases, its radius decreases.
(a) True.
(b) False.
21. White dwarfs with masses in excess of two solar masses have been observed.
(a) True.
(b) False.
22. The size of a typical white dwarf is estimated to be about equal to the size of
(a) a small town.
(b) the Moon.
(c) the Earth.
(d) Jupiter.
23. A white dwarf is composed of
(a) helium.
(b) iron.
(c) carbon nuclei and degenerate electrons.
(d) [None of the above.]
24. The gravitational collapse of a high-density white dwarf is prevented by
(a)
(b)
(c)
(d)
a rapid spin of a white dwarf.
Hebrig-Haro objects.
helium flash.
the pressure created by degenerate electrons.
25. The density of a white dwarf is about
(a) 1011 kilograms per centimeters cubed (i.e., equal to the typical density of an atomic
nucleus.
(b) 1000 kilograms per centimeter cubed.
(c) 10 grams per centimeter cubed (i.e., equal to typical metallic density).
(d) 1 gram per centimeter cubed (i.e., equal to the density of water).
26. There are no hydrogen spectral lines in the spectrum of Type I supernova.
(a) True.
(b) False.
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27. Chandrasekhar’s limit is
(a) the minimum lifetime of a main-sequence star.
(b) the maximum radius of a red giant.
(c) the radius within which an object must shrink to become a black hole.
(d) the maximum mass of a white dwarf.
28. Type I supernova occurs
(a) when a Hebrig-Haro object explodes.
(b) when helium starts fusing into carbon in a star’s core.
(c) when a large mass star explodes.
(d) in a white dwarf-star binary system when the mass transfer pushes the mass of the
white dwarf above the maximum value it can have.
29. The maximum mass that a white dwarf can have is
(a) 0.14 solar masses.
(b) 1.4 solar masses.
(c) 14 solar masses.
(d) [The statement is wrong. A white dwarf can have any mass.]
30. Which of the following sequences describes the evolution of a high mass star
(a) Protostar, main-sequence, yellow giant, red giant, neutron star or a black hole.
(b) Protostar, main-sequence, red giant, yellow giant, red giant, white dwarf.
31. Which is the heaviest element that can be obtained through nuclear fusion of the lighter
ones with a release of energy?
(a) Gold.
(b) Iron.
(c) Silicon.
(d) Carbon.
32. There are no hydrogen spectral lines in the spectrum of Type II supernova.
(a) True.
(b) False.
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33. The structure of a red giant resulting from a high mass star as one goes from its core to
the surface is
(a) uranium, gold, iron, silicon, carbon, helium, hydrogen.
(b) gold, iron, silicon, carbon, helium, hydrogen.
(c) carbon, hydrogen, helium, iron.
(d) iron, silicon, oxygen, carbon, helium, hydrogen.
34. Why does the core of a high mass star collapse?
(a) The iron core’s mass is too small to support the rest of the star.
(b) Because the iron core transforms from solid to liquid.
(c) Because the iron core’s mass becomes so big that degenerate electrons cannot sustain the pressure and combine with protons in the nuclei to produce neutrons and
neutrinos.
(d) [The statement is wrong. The core of a high mass star does not collapse.]
35. Type II supernova occurs
(a) in a white dwarf-star binary system when the mass transfer pushes the mass of the
white dwarf above the maximum value it can have.
(b) when helium starts fusing into carbon in a star’s core.
(c) when a regular star is swallowed by a black hole.
(d) when a large mass stars explodes.
36. Type II supernovae are important because
(a) all of a star’s hydrogen is returned to the interstellar medium.
(b) the elements heavier than iron are synthesized.
(c) the resulting burst of neutrinos keeps the galaxy from collapsing.
(d) they produce helium from hydrogen.
37. Most of supernova 1987A energy output (luminosity) was in the form of visible light.
(a) True.
(b) False.
38. Crab nebula is a supernova remnant.
(a) True.
(b) False.
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39. A pulsar is
(a)
(b)
(c)
(d)
a
a
a
a
protostar just before it becomes a main-sequence star.
fast spinning neutron star.
pulsating yellow giant star.
pulsating iron core of a giant star.
40. What causes the radio pulses of a pulsar?
(a) The star’s orbiting companion periodically eclipses the radio waves emitted by the
main star.
(b) As the star spins, beams of radiation from it sweep through space. If one of these
beams points towards the Earth, we observe a pulse.
(c) The star vibrates.
(d) The star undergoes nuclear explosions that generate radio emissions.
41. According to the General Theory of Relativity, mass/energy curves spacetime.
(a) True.
(b) False.
42. In order to detect a black hole one looks for
(a) a spot into which stars and their planets fall.
(b) a binary system where a companion star is not visible but has a mass greater than
3 solar masses and is an intense X-ray source.
(c) intense source of visible light.
(d) the accompanying white hole.
43. One way astronomers deduce that the Milky Way has a disk is that they
(a)
(b)
(c)
(d)
they can see the centre of our galaxy by naked eye.
see the same number of stars in all directions in the sky.
see far more stars along the band of the milky Way than in other directions.
see stars arranged in a circular region around the north celestial pole.
44. Population II stars are
(a)
(b)
(c)
(d)
bright and hot.
less than 100 million years old.
metal poor.
metal rich.
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45. Harlow Shapley concluded that the Sun was not in the centre of the Milky Way Gal axy
by
(a) looking at the shape of the “milky band” across the sky.
(b) mapping the distribution of stars in the galaxy.
(c) mapping the distribution of gas clouds in the spiral arms.
(d) mapping the distribution of globular clusters in the galaxy.
46. Disk stars are mostly
(a) Population I stars.
(b) Population II stars.
47. Globular clusters are located primarily in the disk of the Milky Way.
(a) True.
(b) False.
48. Open clusters and associations are located primarily in the disk of the Milky Way.
(a) True.
(b) False.
49. Approximately how long does it take the Sun to orbit the Milky Way galaxy?
(a) 23,000 years.
(b) 230,000 years.
(c) 2.3 million year.
(d) 230 million years.
50. Compared with stars in the disk of the Milky Way, orbits of stars in the halo
(a) are elliptical, with random orientation.
(b) are elliptical, but orbiting in the same direction.
(c) do not have to be around galactic centre.
(d) do not have to pass through the plane of the galaxy.
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