Download PH109 Exploring the Universe, Test 3, Fall 2001 Please indicate the

PH109 Exploring the Universe, Test 3, Fall 2001
Please indicate the best answer to the following questions on the answer sheet provided.
1. Magnetic fields inside sunspots are __________ those in surrounding regions.
a) much stronger than, b) slightly stronger than, c) the same as, d) much weaker than
2. The temperature of the layer of gas that produces the visible light of
the Sun is about _______.
a) 15 million K, b) 300,000 K, c) 10 million K, d) 1 million K, e) 5800 K
3. What is the net result of the proton-proton chain?
a) 2 heliums are fused into 1 carbon, 1 neutrinos + energy
b) 4 hydrogens are fused into 1 helium, 2 neutrinos + energy
c) 2 hydrogens and 1 helium are fused into 1 carbon + energy
d) 2 protons and 2 neutrons are fused into 1 carbon + energy
4. Which of the following spectral types is the hottest?
a) G2., b) A5., c) K9., d) O2.
5. Which of the following is the most common type of star?
a) White dwarfs., b) Red giants., c) Main Sequence., d) Supergiants
6. What is the single most important characteristic in determining the course of a star's evolution?
a) Absolute brightness., b) Distance., c) Surface temperature., d) Mass.
7. Why are star clusters almost ideal "laboratories" for stellar studies?
a) The combined light of the stars makes them easier to see.
b) Like our Sun, stars in clusters are always located in the plane of the Milky Way Galaxy.
c) Stars in clusters have the same age, similar composition, and lie at approximately the same
distance away.
d) Stars in clusters are all relatively young and therefore shine brightly.
8. Which event marks the birth of a star?
a) Fusion of hydrogen atoms into helium atoms., b) Collapse of an interstellar cloud.
c) Formation of a photosphere., d) Instability in an interstellar cloud.
9. The final core element for a massive star is
a) carbon, b) oxygen, c) silicon, d) iron
10. What is a planetary nebula?
a) A planet surrounded by a glowing shell of gas.
b) The disc of gas and dust surrounding a young star that will soon form a solar system.
c) The ejected envelope of a red giant surrounding a stellar core remnant.
d) A type of young, medium mass star.
11. A star spends most of its life:
a) As a protostar., b) In explosions lasting millions of years.
c) As a red giant or supergiant., d) As a main sequence star
12. What characteristic of a star cluster is used to determine its age?
a) The number of red giants., b) The faintest stars seen in the cluster.
c) The main sequence turnoff., d) The total number of stars in the cluster.
13. Nearly all the elements found in our environment were formed inside stars. The major exceptions are:
a) Iron and nickel., b) Oxygen and carbon., c) Silver and technetium., d) Hydrogen and helium.
14. An iron core cannot support a star because:
a) Iron has poor nuclear binding energy., b) Iron cannot fuse with other nuclei to produce energy.
c) Iron supplies too much pressure, d) Iron is in the form of a gas, not a solid, in the center of a star.
15. A star can be a supernova:
a) Many times., b) At various times, depending on the mass of the star.
c) Once., d) Early in its evolution.
16. The observed slowing of a clock in the vicinity of a black hole is a prediction of:
a) Special relativity, b) General relativity, c) Stellar nucleosynthesis, d) The Principle of Cosmic Censorship.
17. What explanation does general relativity provide for gravity?
a) Gravity is a result of curved spacetime., b) Gravity is directly proportional to mass.
c) Gravity is inversely proportional to radius., d) Gravity is stronger the faster you go.
18. Sunspots appear dark because
a) they are cooler regions, b) they are concentrations of carbon,
c) their spectrum has been Doppler shifted, d) impurities in the Sun
19. The magnetic field in the Sun gets twisted around the surface because of
a) tidal forces, b) gavitational influnce by the planets,
c) the sun rings like a bell, d) differential rotation
20. Material boiling off the surface of the Sun tends to follow curved trjectories because
a) conservation of angular momentum, b) they follow magnetic field lines,
c) the solar wind blows they around, d) the curved surface of the Sun
21. The source of energy in the core of the Sun is nuclear fusion. How many Hydrogen nuclei does it take
to make one Helium nuclei
a) four, b) nine, c) one, d) Hydrogen does not make Helium
22. In relative terms, how does the Sun's size compare to all other stars
a) tends to be on the smaller side, b) tends to be on the larger side,
c) tends to be in the middle, d) we can't measure the size of other stars
23. In relative terms, how does the Sun's temperature compare to all other stars
a) tends to be on the hot dise, b) tends to be on the cool side,
c) tends to be in the middle, d) we can't measure the temperatures of other stars
24. What is the correct sequence of spectral types of stars according to temperature
a) OBAFGKM, b) OFGBGMA, c) FABOGKM, d) ABFGKMO
25. In order to measure the mass of a star what must be true
a) it must be spectral type O or B, b) it must be a main sequence star,
c) it must be close to Earth, d) it must be a binary
26. Which spectral type of star has the longest life on the main sequence
a) O, b) F, c) K, d) M
27. Star A and star B have the same luminosity but star A is four time brighter than star B. What must be
true.
a) they have different spectral types, b) star b is twice as far away,
c) star A is exploding, d) star A is moving toward us
28. When the electron and proton go from alinged spins to opposite spins in the Hydrogwen atom. What
happens?
a) nuclear fusion, b) nuclear fission, c) 21 cm radiation, d) E=MC 2
29. The most common elemen found in the interstellar medium is
a) Hydrogen, b) Helium, c) Carbon, d) ammonia
30. The bubbling of the Sun's surface is seen as
a) solar wind, b) solar flares, c) granulation, d) corona
31. All stars with masses equal to or greater than the sun expand to become
a) red giants, b) super novae, c) white dwarfs, d) blue giants
32. About how old do astronomers think the sun is
a) 10 billion years, b) 5 billion years, c) 10 million years, d) 5 millions years
33. A measurement of the parallax of a star allows us directly to determine the star's
a) rotation rate, b) temperature, c) distance, d) age
34. The stars located in the lower left corner of the HR diagram are
a) white dwarfs, b) main sequence stars, c) giants, d) supergiants
35. The four hydrogen nuclei which are fused together are more massive than the helium nucleus which
they make. What happens to the missing mass?
a) it is converted to energy, b) it is ejected from the star in flare activity
c) it reappears later as neutrinos, d) it is resupplied to the Sun by meteoroid impacts
36. What do all main sequence stars have in common?
a) they are all yellow, b) they are all consuming hydrogen in their cores
c) they are located near the Sun in space, d) they are all among the most luminous stars
37. Pulsars are
a) spinning neutron stars with beamed radio emission, b) black holes with accretion disks
c) pulsating red giant stars with close companions, d) white dwarfs with periodic stellar winds
38. If the Sun were replaced by a black hole having a mass of one solar mass, what would happen to the
Earth's orbit?
a) the Earth would spiral inward, b) the Earth would jump to a smaller orbit
c) the size of the Earth's orbit would increase rapidly, d) the Earth's orbit would remain the same
39. A star which is discovered to be a binary system on the basis of the Doppler shifts of the spectral
lines of its two stars is called a
(a) spectroscopic binary, (b) astrometric binary, (c) visual binary, (d) eclipsing binary
40. The 21 cm line is emitted by
a) hydrogen atoms, b) interstellar dust, c) a gas of hot protons and electrons, d) CO molecules