Astronomy - Test 3
Spring 2013
Test form A
Name ________________________
Do not forget to write your name and fill in the bubbles with your student number, and
fill in test form A on the answer sheet. Write your name above as well. You have 55
minutes. For each question, mark the best answer. The formulas you may want are:
3.26 ly
d
p
4
L T   R 
  

L  T   R 
2
L = 4d2B
1. The most common type of star is a
A) Neutron star B) White dwarf C) Giant D) Supergiant E) Main sequence
2. At right is sketched a Hertzsprung-Russell
diagram for four clusters. Which cluster is
probably the oldest?
A) A
B) B
C) C
D) D
E) Insufficient information
D
C
B
A
3. It is common for stars to have spectral lines corresponding to those expected for
hydrogen, but shifted slightly to either longer wavelengths or shorter wavelengths.
What is the likely cause of this slight shift?
A) Gravitational red-shift caused by the star’s gravity
B) Pressure effects from the high pressure of the hydrogen
C) Doppler shift caused by the motion of the star
D) Isotopic shift caused by the star having 2H instead of standard 1H
E) Thermal broadening caused by the high temperature of the star
4. For which types of stars can we measure the mass of the star?
A) White dwarfs
B) Protostars
C) Binary stars
D) Nearby stars
E) Spectral class B stars
5. What mechanism is primarily responsible for transporting heat in the Sun?
A) Radiation everywhere
B) Convection everywhere
C) Conduction everywhere
D) Radiation near the center, convection near the surface
E) Convection near the center, radiation near the surface
6. A typical high-quality visible light picture of the Sun shows what features, if any?
A)
B)
C)
D)
A plain ball with normally no features
A ball but with relatively small dark spots called sunspots
A ball but with relatively small bright spots called sunspots
A ball but with stripes representing zones and bands at slightly different
brightness
E) A ball but with stripes representing zones and bands with slightly different colors
7. Some stars fuse helium to carbon in their core. Why doesn’t the Sun do this?
A) The Sun has very little helium in it
B) This Sun doesn’t have a strong enough magnetic field for this
C) The Sun’s convection is too slow to collide helium atoms with enough speed
D) This process requires oxygen as a catalyst, and the Sun has very little oxygen
E) The Sun is not hot enough for helium fusion
8. What distinguishes a plasma, such as the Sun is made from, from an ordinary gas?
A) Plasmas are hot enough for nuclear fusion, gasses are not
B) Plasmas are made mostly of hydrogen, gasses are not
C) Plasmas are hot enough that the electrons have come loose from their atoms,
gasses consist of neutral atoms
D) Gases are made of diatomic molecules like O2 or N2, plasmas are made of
monatomic molecules like He or Ar
E) Gases conduct electricity, plasmas do not
9. What clues can tell us about what is going on in the interior of the Sun?
A) The magnetic fields of the Sun (only)
B) Neutrinos produced in the core of the Sun (only)
C) Vibrations of the Sun, or helioseismology (only)
D) All of the above
E) None of the above
10. Which of the following stars have hydrogen burning to helium at their centers?
A) Main sequence stars (only)
B) Red giant stars (only)
C) Double-shell burning stars (only)
D) Main sequence and red giants, but not double-shell burning stars
E) Main sequence, red giants, and double-shell burning stars
11. Why have we never observed red giant stars much lighter than the Sun, say, with less
than half a solar mass?
A) Stars with this low a mass would not yet have reached the red giant stage
B) Low mass stars are so difficult to observe we probably wouldn’t have noticed
them
C) Such low mass stars never evolve to giant stages
D) These stars explode as supernovas before reaching the giant stages
E) These stars form blue giant stars, no red
12. What event triggers the transition from a red giant stage to the next stage in a star’s
evolution?
A) The core runs out of hydrogen
B) The core runs out of helium
C) The helium begins burning to carbon (and oxygen)
D) The hydrogen begins burning to carbon (and oxygen)
E) The carbon begins burning to neon
13. How does the length of the late stages of the Sun compare with the main sequence?
A) The late stages all take much longer than the main sequence
B) The late stages are each about the same length as the main sequence
C) Some of the late stages are much longer, and some are much shorter
D) The late stages all are much shorter than the main sequence
E) Scientists do not know, as the Sun is still a main sequence star
14. A typical star like the Sun has what kind of spectrum?
A) dark line B) bright line C) continuous thermal D) polarized E) white noise
15. Which of the following might be a spectral type of a star?
A) G7
B) C3
C) F17
D) 3B
E) FG
16. The two stages of a low mass star’s life when it is the largest are red giant and
A) White dwarf
B) Double shell burning
C) Main sequence
D) Core helium burning
E) Neutron star
17. The force that keeps a white dwarf from collapsing to a point is:
A) Pressure caused by the high temperature
B) The electric repulsion of the nuclei
C) The electric repulsion of the electrons
D) Degeneracy pressure of the nuclei
E) Degeneracy pressure of the electrons
18. Which gives us the most reliable and extensive information about what elements the
Sun is made from?
A) Measuring the magnetic fields around the Sun
B) Studying the composition of the Solar wind
C) Samples gathered by sun-grazing satellites
D) We assume the composition is similar to the composition of other solar system
objects, like Jupiter
E) Studying the solar spectrum
19. Which of the following approximately describes the distance technique called
parallax for measuring the distance to stars?
A) Measure the angle of the star as viewed from two distant places on the Earth
B) Measure the angle of the star as viewed from two positions of its orbit around the
Sun
C) Measure the brightness of the star and its spectral class, and compare to the Main
Sequence curve on the Hertzsprung-Russell diagram
D) Send a radio signal to the star and measure how long it takes to return
E) Measure the angular size of the star and compare to a theoretical model of its
actual radius
20. The three most common elements comprising the Sun, in decreasing order of
abundance, are
A) Hydrogen, oxygen, helium
B) Hydrogen, helium, oxygen
C) Helium, hydrogen, oxygen
D) Helium, oxygen, hydrogen
E) Oxygen, helium, hydrogen
21. If you compare the overall history of a one- and two-solar mass star, how will they
compare?
A) They are very different, with the light one ending as a white dwarf and the heavy
one ending with a supernova
B) They are very different, with the light one ending as a supernova and the heavy
one ending as a white dwarf
C) They will follow similar paths, ending as supernovae, but the light star goes faster
D) They will follow similar paths, ending as a white dwarf, but the heavy star goes
faster
E) They will follow similar paths, ending as a white dwarf, but the light star goes
faster
22. Which of the following is a way that a star can explode to make a supernova?
A) The core of a very massive star begins to collapse (only)
B) Carbon in the core of a star reaches a temperature to begin fusing to neon (only)
C) A white dwarf accreting matter from a companion star exceeds the maximum
mass (only)
D) Both A and B are correct, but not C
E) Both A and C are correct, but not B
23. Plasma ejected from the Sun often forms arch-like structures called prominences.
Why are they arch-like?
A) The plasma is ejected from the Sun, and gravity bends it into an arch
B) The only stable shape held up by pressure is an arch
C) The plasma is following magnetic field lines, which form arches
D) The Corona has negative pressure, which pulls it into an arch shape
E) It’s a promotion by the McDonald’s corporation
24. Which of the following might be ways to make black holes?
A) A very massive star (30+ solar masses or so) undergoes gravitational collapse
(only)
B) A neutron star accretes matter from a companion star (only)
C) Two neutron stars that are very close together merge (only)
D) A and B are correct, but not C
E) A, B, and C are all correct
25. As it moves towards the main sequence, a protostar gets
A) Smaller and cooler
B) Bigger and cooler
C) Smaller and hotter
D) Bigger and hotter
E) Protostars change little
26. An object that has less mass than a star but more mass then a planet is called a
A) brown dwarf B) white dwarf C) neutron star D) black hole E) protostar
27. Star A and star B appear to be the same brightness, even though star A is four times
farther away than star B. How many times more luminous is star A than star B?
A) 1
B) 2
C) 4
D) 16
E) 256
28. Which of the following techniques has been used to find more than half of all
extrasolar planets?
A) Direct imaging, where you just see the planet directly
B) Stellar timing, where you notice if the star’s regular signals are coming early or
late
C) Astrometry, where you note that the star moves from side to side from the
influence of the planet’s gravity
D) Gravitational microlensing, where the planet’s gravity magnifies the light from a
distant star
E) Doppler method, where the planet is deduced from the Doppler shift of the star’s
spectrum
29. The Sun, of course, currently has a mass of one solar mass. Why is it that when the
Sun dies, it will be expected to have a smaller mass, about 0.6 solar masses?
A) Nuclear fusion will have consumed about forty percent of the hydrogen
B) Neutrinos carry off a large fraction of the mass
C) Passing stars will gravitationally extract some of the mass of the Sun
D) During late stages, stars like our Sun have large mass loss through strong solar
winds
E) The center of the Sun will have collapsed to a black hole
30. Which of the following is not a huge cloud, much larger than an ordinary star?
A) Molecular cloud
B) Neutron star
C) Supernova Remnant
D) Planetary Nebula
E) Actually, all of these are huge clouds
31. Star A is spectral class A5 and star B is spectral class B5. They have the same
brightness. They are both main sequence stars. Which star is farther away?
A) Star A
B) Star B
C) They are equal distance away
D) You can’t tell unless you also know the luminosity
E) You can’t tell, even if you know the luminosity
32. How come the technique of spectroscopic parallax cannot be used to measure the
distance to the star Betelgeuse, a red supergiant that is about 650 light years away?
A) The parallax angle would be too small at this distance
B) A star at this distance would be too dim for this technique
C) It would take 650 years to collect the spectrum, far too long to be practical
D) This technique requires a full spectrum, but red stars have only red light
E) Spectroscopic parallax can only be used for main sequence stars, not supergiants
33. Just before the core of a massive star begins to collapse to make a supernova, the core
of the star is made of
A) Carbon
B) Silicon
C) Iron D) Helium
E) Neutrons