MIDTERM #1
AST209 - The Cosmos
Feb 10, 2012
50 minutes duration
Answer all THIRTY SIX questions on a bubble sheet provided.
Make sure you put your name and ID number on the bubble sheet.
Use pens to fill in the bubbles. Pencils will work as well but please
ensure that you fill in the bubbles completely.
Do NOT Punch holes in the bubble sheets.
Each question is worth 1 point.
This is a closed book exam but any kind of calculator (including scientific
ones) is allowed.
DO NOT OPEN THE EXAM BOOKLET UNTIL
INSTRUCTED TO DO SO BY THE
INSTRUCTOR.
FAILURE TO COMPLY WILL RESULT IN YOUR
EJECTION FROM THE EXAM ROOM AND A
GRADE OF ZERO ON THE EXAM.
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
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1. He discovered that Jupiter has moons.
A) Ptolemy
B) Kepler
C) Tycho Brahe
D) Galileo
E) Aristotle
2. What is the range of values for Right Ascension?
A) 0 to 23 hours
B) 90 degrees to 0 degrees
C) 0 to 360 degrees
D) 0 to 12 hours
E) +23.5 to -23.5 degrees
3. What is a circumpolar star?
A) a star that makes a daily circle around the celestial sphere
B) a star that is close to the north celestial pole
C) a star that always remains above your horizon
D) a star that is close to the south celestial pole
E) A star that is visible from the Arctic or Antarctic circles
4. A person orbiting the Earth in the Space Shuttle feels weightless because
A) her mass is zero in space, and weight requires mass.
B) only one force (gravity) acts on her, but gravity also accelerates the Shuttle so the Shuttle does not
push up on her to create the feeling of weight.
C) two forces are acting on her in opposite directions, so they cancel and produce the same effect as if no
force at all were acting.
D) no forces act on her
5. If the line joining a planet to the Sun sweeps out a particular area in one day, then in two days it will sweep
out
A) less than twice the area if the planet is approaching perihelion and more than twice the area if it is
leaving perihelion.
B) more than twice the area if the planet is approaching perihelion and less than twice the area if it is
leaving perihelion.
C) half the area.
D) exactly twice the area.
6. According to Newton's third law, if a force is acting on an object, then
A) the object must move in a circular path.
B) the object must accelerate.
C) there must be some other force also acting on the object, with the same magnitude but in the opposite
direction.
D) there must be some other force acting on a different object, with the same magnitude but in the
opposite direction.
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7. By locating the north celestial pole (NCP) in the sky, how can you determine your latitude?
A) The direction of the NCP is the same as your latitude.
B) The altitude of the NCP is your angular distance from the North Pole.
C) The altitude of the NCP is the same as your latitude.
D) The direction of the NCP is the angular distance from the North Pole.
E) The altitude of the NCP is the same as your distance from the North Pole.
8. The ecliptic can be defined as
A) the path traced out by the Sun in our sky over one year against the background stars.
B) the extension of the Earth's equator onto the sky.
C) the plane which is perpendicular to the Earth's spin axis.
D) the path traced out by the Moon in our sky in one month against the background stars.
9. Which of the following is largest?
A) distance to the nearest star (other than our Sun)
B) size of Pluto's orbit
C) size of a typical galaxy
D) 1 light-year
10. THIS IS VERSION A OF THE EXAM. FILL IN THE A BUBBLE AS THE "ANSWER" TO THIS
QUESTION.
A) A
B) B
C) C
D) D
11. Which of the following statements does not use the term light-year in an appropriate way?
A) The Milky Way Galaxy is about 100,000 light-years in diameter.
B) It's about 4 light-years from here to Alpha Centauri.
C) It will take the Voyager spacecraft about 20,000 years to travel just 1 light-year.
D) It will take me light-years to complete this homework assignment.
E) A light-year is about 10 trillion kilometers.
12. What causes the apparent retrograde motion of the planets?
A) The other planets never really appear to move backward; the background stars shift due to Earth's
revolution around the Sun.
B) As Earth passes another planet, its gravitational pull slows down the other planet so that it appears to
be traveling backward.
C) Apparent retrograde motion is an illusion created by turbulence in Earth's atmosphere.
D) When planets are farther from the Sun, they move slower than when they are nearer the Sun; it is
during this slower period that they appear to move backwards.
E) As Earth passes another planet, the other planet appears to move backward with respect to the
background stars, but the planet's motion does not really change.
13. How are wavelength, frequency, and energy related for photons of light?
A) Longer wavelength means lower frequency and higher energy.
B) There is no simple relationship because different photons travel at different speeds.
C) Longer wavelength means higher frequency and lower energy.
D) Longer wavelength means lower frequency and lower energy.
E) Longer wavelength means higher frequency and higher energy.
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14. From lowest energy to highest energy, which of the following correctly orders the different categories of
electromagnetic radiation?
A) radio, infrared, visible light, ultraviolet, X rays, gamma rays
B) infrared, visible light, ultraviolet, X rays, gamma rays, radio
C) radio, X rays, visible light, ultraviolet, infrared, gamma rays
D) gamma rays, X rays, visible light, ultraviolet, infrared, radio
E) visible light, infrared, X rays, ultraviolet, gamma rays, radio
15. Which of the following statements about stellar parallax is true?
A) It takes at least 10 years of observation to measure a star's parallax.
B) The closer a star is to us, the more parallax it exhibits.
C) Stellar parallax was first observed by ancient Greek astronomers.
D) The amount of parallax we see depends on how fast a star is moving relative to us.
E) We observe all stars to exhibit at least a slight amount of parallax.
16. If an astronaut landed on a planet of the same radius as the Earth but four times the mass, then the
astronaut's mass on the planet would be
A) four times her mass on the Earth.
B) sixteen times her mass on the Earth.
C) the same as on Earth, because mass is independent of location.
D) twice her mass on the Earth.
17. Which path would a planet (like Earth!) take if the force of gravity from the Sun were to be suddenly
removed?
A) The planet would begin to move in a long ellipse with the Sun at one focus.
B) The planet would stop moving altogether because there would be no gravity acting upon it.
C) The planet would move in a straight line tangential to its present orbit.
D) The planet would move in a straight line outward, directly away from the Sun's position.
18. Which wavelength region of the electromagnetic spectrum is taken up by visible light?
A) 400 nm to 700 nm.
B) 1200 nm to 1500 nm.
C) 4000 nm to 7000 nm.
D) 100 nm to 400 nm.
19. The mass of Jupiter can be calculated by
A) measuring the orbital speed of one of Jupiter's moons.
B) measuring the orbital period and distance of Jupiter's orbit around the Sun.
C) knowing the Sun's mass and measuring how Jupiter's speed changes during its elliptical orbit around
the Sun.
D) measuring the orbital period and distance of one of Jupiter's moons.
E) knowing the Sun's mass and measuring the average distance of Jupiter from the Sun.
20. Star A has a temperature 3 times that of star B. Both star A and star B are the same physical size. Which
statement about star A and star B below is correct?
A) Star A is redder and dimmer than star B.
B) Star A is bluer and dimmer than star B.
C) Star A is bluer and brighter than star B.
D) Star A is redder and brighter than star B.
E) Star A and star B have the same color, but star A is brighter.
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21. The declination of a star in our sky is defined as
A) the angle between the Sun and the star, measured along the ecliptic plane.
B) the angle between the great circle passing through the star and both celestial poles and the equivalent
great circle through the Vernal Equinox, measured along the celestial equator.
C) the angle between the celestial equator and the star, measured along a great circle passing through
both celestial poles
D) the angle between the position of the center of the galaxy and the star, measured along the galactic
plane.
22. In modern astronomy, the constellations are
A) 13 specific regions of stars through which the planets and Moon appear to move in our sky.
B) specific patterns of stars which point to certain directions that are useful for navigation.
C) a small number of well-defined and separate groups of stars in our sky.
D) 88 non-overlapping sky regions, covering the whole sky.
23. The frequency of a wave is
A) measured in cycles per second.
B) the number of peaks passing by any point each second.
C) measured in hertz (Hz).
D) equal to the speed of the wave divided by the wavelength of the wave.
E) all of the above
24. How many arcseconds are in 1°?
A) 60
B) 10,000
C) 3,600
D) 360
E) 100
25. When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting
A) dimmer.
B) brighter.
C) lower in the sky.
D) higher in the sky.
26. On which of these assumptions do Ptolemy and Copernicus agree?
A) All orbits must be perfect circles.
B) The Sun was bigger than the Earth.
C) Venus must always stay between us and the Sun.
D) The Earth must be the center of all motion in the Cosmos.
E) The Sun must orbit us, but the planets do orbit the Sun.
27. The heliocentric model was actually first proposed by:
A) Alexander the Great.
B) Aristotle.
C) Aristarchus.
D) Archimedes.
E) Hipparchus.
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28. Two spaceships that have different masses but rocket engines of identical force are at rest in space. If they fire
their rockets at the same time, which ship will speed up faster?
A) The one with the lower mass.
B) They will increase speed at the same rate, because they have identical rocket engines.
C) They will not speed up at all, but move at a constant speed because they are in space and the rocket
has nothing against which to push.
D) It is impossible to say with only the information provided
E) The one with the higher mass.
29. Why is it summer in the Northern Hemisphere when it is winter in the Southern Hemisphere?
A) The Northern Hemisphere is tilted away from the Sun and receives more indirect sunlight.
B) The Northern Hemisphere is "on top" of Earth and therefore receives more sunlight.
C) The Northern Hemisphere is closer to the Sun than the Southern Hemisphere.
D) The Northern Hemisphere is tilted toward the Sun and receives more direct sunlight.
E) It isn't: both hemispheres have the same seasons at the same time.
30. The Ptolemaic model of the universe:
A) could not account for the stellar parallax observed by Hipparchus.
B) always kept Mars and Mercury between the Earth and Sun.
C) is the basis of our modern cosmology.
D) explained and predicted the motions of the planets with deferents and epicycles.
E) describes the orbits of the planets as being ellipses, not circles.
31. Which of the following statements about the celestial equator is true at all latitudes?
A) It represents an extension of Earth's equator onto the celestial sphere.
B) It lies along the band of light we call the Milky Way.
C) It extends from your horizon due east, through your zenith, to your horizon due west.
D) It extends from your horizon due north, through your zenith, to your horizon due south.
E) It cuts the dome of your local sky exactly in half.
32. [CALCULATION] A planet of mass 8MEarth orbits around a star of mass 5MSun at a distance of 1.5 AU. The
gravitational force on this planet due to the star would be
A) 1/26.7 times that which the Sun exerts on the Earth
B) it is impossible to say with only the information provided
C) 26.7 times that which the Sun exerts on the Earth
D) 1/17.8 times that which the Sun exerts on the Earth
E) 17.8 times that which the Sun exerts on the Earth
33. [CALCULATION] What is the distance to a star that has an observed parallax of 0.042"? Assume that the
observations have a baseline of 1 AU.
A) 4,911,066.8 pc
B) 23.8 AU
C) 23.8 pc
D) 1,364 AU
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34. [CALCULATION] You observe one of Mar's moons (Phobos) to obrit around Mars once every 7 hours and
39 minutes (0.3189 days). You also measure its orbital distance to be 9337 km (from the center of Mars).
What is the mass of Mars? (assume 365.25 days in a year).
A) 6.3x10 23 Kg
B) 1.3x10 24 Kg
C) 8x1012 Kg
D) 1.3x10 22 Kg
35. [CALCULATION] - The Crab Nebula, has an angular size of about 5.5' and is at a distance of 6300 light
years. What is the true size of the Crab Nebula
A) 0.1 light years
B) 10 light years
C) 605 AU
D) 605 light years
E) 0.0017 light years
36. [CALCULATION] - You measure the Black Body spectrum of a distant star and find that its peak
wavelength is 200 nm. What is the surface temperature of this star?
A) 69,000 K
B) 14,500 K
C) it is impossible to say with only the information provided
D) 6900 K
E) 1.4x10 -5 K
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Answer Key
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