Spring 2013
Astronomy - Test 1
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 50
minutes. For each question, mark the best answer. The formulas you may want are:
GMm
F = ma
d2
c = f
c = 3108 m/sec
vrad shift  rest

c
rest
F
P2 = a3
(M + m) P2 = a3
E = hf
P = knT
maxT = 2900 Km
1. If we place some gas in a tight container and heat it up, the pressure increases
because
A) Heating increases the number of gas molecules
B) The gas molecules move faster, and bounce off the walls with more force
C) The gas releases electromagnetic energy (light) which pushes against the walls
D) The gas molecules expand, pressing outwards against the container walls
E) The repulsive forces between the gas molecules increase, pushing them apart
2. In vacuum, as you increase the frequency f of light, the speed of light
A) Increases
B) Decreases
C) Stays the same
D) Increases at high frequencies; decreases at low frequencies
E) Decreases at high frequencies; increases at low frequencies
3. The Moon will undergo a lunar eclipse around April 25 of this year. In the cycle of
phases of the moon, this must occur near
A) Full moon (only)
B) New moon (only)
C) Full moon or new moon
D) Neither full moon nor new moon
E) Insufficient information
4. When two objects are gravitationally bound, such as Pluto and its moon Charon, what
determines which one is orbiting and which one stands still as it is orbited?
A) The one which is initially moving faster is the one that orbits
B) The one which is initially moving slower is the one that orbits
C) The one which has less mass orbits
D) The one which has more mass orbits
E) Actually, they both orbit each other, or more accurately, they both orbit the center
of mass
5. Which of the following marks one difference between electric forces and gravity?
A) Gravity is generally much stronger than electromagnetism
B) Gravity is always attractive, while electric forces can attract or repel
C) Electric forces are always attractive, while gravity can attract or repel
D) Gravity acts only on short distances, electric forces can work over long distances
E) Gravity does not affect neutrons, electric forces do
6. Which of the following is a good reason to put a telescope into space?
A) The atmosphere blocks many types of radiation (only)
B) You are closer to the galaxies and stars you want to see (only)
C) You can avoid light pollution (only)
D) A and B are valid, but not C
E) A and C are valid, but not B
7. Which of the following is evidence that ancients could use to tell that the Moon is a
sphere, not a flat disk?
A) The shape of the darkening of the Sun during solar eclipses
B) The way the Moon was illuminated throughout the month
C) The shape of the Earth’s shadow on the Moon during Lunar eclipses
D) The fact that the Moon went around the Earth about once a month
E) None of the above; the ancient’s didn’t figure out that Moon is a sphere
8. According to Newton, objects in orbit around another body can follow an ellipse, a
hyperbola, or a parabola. Nonetheless, all the planets follow ellipses. Why is that?
A) Newton’s laws were ultimately replaced by the more correct Kepler’s laws, which
only allow ellipses
B) The planets are all moving more slowly than escape velocity from the Sun
C) Because the planets all have positive masses, they produce elliptical orbits. To
get a hyperbolic or parabolic orbit, you would have to have negative masses
D) They actually follow ellipses most of the time, and the other shapes only a small
amount of the time, but they actually do both
E) Objects must be very far away to follow hyperbolas or parabolas, and all the
planets are closer than that
9. If you have one photon of electromagnetic radiation, which of the following would
have the highest energy?
A) Radio
B) Microwaves C) Visible
D) Gamma rays E) X-rays
10. What technique is commonly used with the largest visible light telescopes based on
the Earth to minimize blurring?
A) Selective imaging – Only pick pointlike objects to image, like stars
B) Vacuum penetration – A small, brief hole is drilled through the atmosphere,
eliminating the distortion
C) Adaptive optics – the primary mirror’s shape is constantly adjusted to compensate
for the atmospheric distortion
D) Pinhole optics – a mask with a tiny hole is placed over the telescope, so only light
that is going perfectly straight can make it to the imaging system
E) Tranquil optics – images are only taken when the atmosphere is perfectly still, so
there is no distortion
11. What huge advantage did Galileo have over previous astronomers, like Tycho Brahe,
that allowed him to convincingly demonstrate that Venus went around the Sun, not
the Earth?
A) He had the support of the church, so he was not at risk of heresy
B) He was a much more careful observer than Tycho Brahe
C) He was able to use calculus, since he had learned it from Newton
D) He demonstrated that white light is actually made of a mixture of many different
colors
E) He used a telescope, which was not available before his time
12. Compared to the stars, which of the following objects sometimes move west to east
and sometimes east to west?
A) The Sun (only)
B) The Moon (only)
C) The Planets (only)
D) The planets and the Moon, but not the Sun
E) The planets and the Sun, but not the Moon
13. Which of the following would increase the force between the Earth and the Moon by
a factor of four?
A) Doubling the mass of the Moon
B) Doubling the mass of the Earth
C) Increasing the distance between them by a factor of two
D) Decreasing the distance between them by a factor of two
E) Decreasing the distance between them by a factor of four
14. What is the wavelength  of a wave?
A) How many times per second the wave repeats
B) How far it is from one peak to the next of the wave
C) How fast the wave is moving
D) How much time it is from when one peak of a wave passes to the next peak
E) How many waves can fit into each meter of space
A
15. A comet orbits the Sun following the ellipse sketched at right,
D
going clockwise. At which point will the comet be moving fastest?
A) A
B) B
C) C
D) D
E) The speed is constant
C
B
16. Which of the following proves that at least some planets go around the Sun, rather
than the Earth?
A) The planets get brighter and dimmer
B) Some planets, like Venus, go through a full cycle of phases
C) The planets sometimes move prograde, and sometimes retrograde
D) Some planets, like Venus, are never at a large angle from the Sun
E) Jupiter has moons that go around it
17. Star A has a thermal spectrum with the peak of its spectrum at 400 nm. Star B has a
thermal spectrum with the peak of its spectrum at 800 nm. The two stars are equally
bright. Which star has a higher surface temperature?
A) Star A
B) Star B
C) They have equal surface temperature
D) Without knowing the radius, there is insufficient information to figure out
E) There is insufficient information, even if you knew the radius
18. Which of the following is not a category of electromagnetic radiation?
A) Visible light
B) Radio C) Ultrasound D) X-rays
E) Gamma rays
19. The Moon goes through its cycle of phases in about a (an)
A) hour
B) day
C) week
D) fortnight (14 days)
E) month
20. Every calcium atom, whether neutral or not, must have exactly the same
A) Nuclear charge (only)
B) Number of electrons (only)
C) Nuclear charge AND number of electrons
D) Number of neutrons
E) Energy
21. Which of the following effects can cause the frequency of light from an astronomical
source to be shifted to a much longer wavelength?
A) If there is a hot source between us and the object
B) If there is a cold source between us and the object
C) If the object is moving towards us at high speed
D) If the object is moving away from us at high speed
E) If the object is moving perpendicular to us
22. Hydrogen produces a variety of spectral lines, at least one of which is red and one of
which is blue. How do the transitions of the electrons in hydrogen differ that cause
the red and blue lines?
A) The red line transition must be occurring faster than the blue line transition
B) The red line transition must be occurring slower than the blue line transition
C) The red line transition must involve a smaller energy change than the blue line
transition
D) The red line transition must involve a larger energy change than the blue line
transition
E) The red line transition must be from different kind of hydrogen atom than the blue
line transition
23. Why do radio astronomers commonly combine the radio signals from radio dishes
that are far apart, sometimes even thousands of kilometers apart?
A) It allows them to see distant objects from two different angles, giving them a
three-dimensional view of it
B) They can combine the signals using interferometry, letting them see much finer
details than a single radio telescope could
C) It allows them to avoid interference from clouds and so on; if one is in a cloudy
location, the other might be clear
D) By bouncing the signal back and forth several times between the two radio dishes,
they can amplify it many times
E) It is simply error checking, if they all see the same thing, it must not be
instrumental error
24. A hot, thin gas produces what type of spectrum?
A) A continuous spectrum
B) An absorption, or dark line spectrum
C) An emission, or bright line spectrum
D) A white noise, or 1/f spectrum
E) A top hat, or finite spectral distribution spectrum
25. If you were trying to figure out the surface temperature of a star, the best indicator of
it would be its
A) Color
B) Distance
C) Brightness D) Altitude
E) Azimuth
26. Which of the following statements makes sense, in terms of units?
A) The physical diameter of the Sun is about 30 arc-minutes
B) The time it takes light to get to us from the sun is about 30 arc-minutes
C) The brightness of the Sun is about 30 arc-minutes
D) The apparent angular size of the Sun is about 30 arc-minutes
E) The average amount of time it takes to complete this test is about 30 arc-minutes
27. Which of the following would be a good way to tell if the star Betelgeuse has any
iron in its composition?
A) Measure the overall color of the star Betelgeuse
B) Measure the total mass and radius of Betelgeuse, and compare with the density to
iron
C) Measure the magnetic field produced by Betelgeuse
D) Compare the albedo (shininess) of Betelgeuse with iron
E) Measure the spectral lines of Betelgeuse, and compare with the spectral lines of
iron here on Earth
28. What would happen to Earth’s Moon if it happened to stray too close to Earth, inside
the Roche limit?
A) It would be broken in half, then the halves would break in half, and soon, until
ultimately it became a ring
B) It would be ejected from Earth, leaving and never coming back
C) It would break into two approximately equally sized pieces, which would then
orbit the Earth as two moons
D) It would get sucked into the Earth, catastrophically destroying life on Earth
E) Nothing, since it is solid, Earth cannot affect its shape
29. The high temperature today (Friday) is probably somewhere around
A) 0.287 K
B) 2.87 K
C) 28.7 K
D) 287 K
E) 2870 K
30. Mercury orbits the Sun with an average distance that is less than the average distance
of Venus from the Sun. From this alone, we can conclude that
A) Venus takes more time to orbit the Sun than Mercury
B) Venus takes less time to orbit the Sun than Mercury
C) Venus is hotter than Mercury
D) Venus is cooler than Mercury
E) None of the above can be concluded from the information given
31. Spring tides (especially high and low tides) occur typically
A) Around full moon (only)
B) Around new moon (only)
C) Around first quarter (only)
D) Around first or third quarter
E) Around new moon and full moon
32. Which of the following is not a kind of energy we have at least discussed?
A) Light
B) Nuclear C) Kinetic D) Gravitational E) Quantum Mechanical
33. According to Newton’s Laws, what would a planet do if not for the gravity of the
Sun?
A) It would gradually spiral in towards the Sun
B) It would slowly lose speed and stop
C) It would move in a straight line forever, leaving the Sun
D) It would move in a direct line away from the Sun, gradually accelerating
E) It would gradually spiral away from the Sun