29:50 Stars, Galaxies & the Universe
Practice Exam

1. The astronomical unit is defined as
   (a) the diameter of the planet Earth.
   (b) the average diameter of the Jovian planets.
   (c) the mean distance of the Sun from the center of the Milky Way galaxy.
   (d) the mass of the Sun, which is used as a scale for stellar masses.
   (e) the average distance between the Earth and Sun.
   

2. The ecliptic is best described as
   (a) the non-circular orbital paths that the planets in our Solar System follow.
   (b) the amount by which a planet’s orbit is non-circular.
   (c) something that strays from the normal path.
   (d) the additional circle that Ptolemy and Copernicus added to the orbital paths of the planets to make the observations match theory.
   (e) the path of the Sun (Moon, and planets) through the sky from an observer’s perspective on Earth.

3. The seasons are caused by
   (a) annual variations in the distance between the Earth and Sun.
   (b) the tilt of the Earth's axis relative to its orbital plane.
   (c) a ``heartbeat'' of the Sun which causes its brightness to change during a year.
   (d) the rotation of the Earth on its axis.
   (e) the revolution of the Earth about the Sun.
   

4. If a planet identical to the Earth were discovered at 0.5 AU (between Mercury and Venus), how would the gravitational pull by the Sun on that planet compare to what we experience on Earth from the Sun?
   (a) the gravitational force would be ¼ of what the Earth experiences
   (b) it would not change gravitational force does not depend on distance
   (c) the gravitational force would be 4x of what the Earth experiences
   (d) the gravitational force would be 2x of what the Earth experiences
   (e) the gravitational force would be ½ of what the Earth experiences

5. An example of a space-based telescope is:
   (a) The Very Large Array.
   (b) Arecibo Observatory.
   (c) The W.M. Keck Observatory.
   (d) The Chandra X-ray Observatory.
   (e) none of the above.
   
6. Which of the following arrangements correctly organize electromagnetic radiation in order of decreasing wavelength:
   (a) radio, gamma rays, visible, infrared, ultraviolet, microwaves, xrays
   (b) xrays, gamma rays, ultraviolet, visible, infrared, microwaves, radio
   (c) microwaves, infrared, radio, visible, xrays, gamma rays, ultraviolet
   (d) radio, microwaves, infrared, visible, ultraviolet, xrays, gamma rays
   (e) none of the above are correct.
   

7. One of the laws of physics that is highly useful in astronomy is Wien's Law. Wien's Law says that there is a mathematical relation between
   (a) where absorption lines are seen and the chemical nature of the object.
   (b) the mass of a star and its luminosity.
   (c) the wavelength of light and its frequency.
   (d) the radius of an object and its mean density.
   (e) the temperature of an object and the wavelength at which it is brightest.
   

8. The two main windows in the Earth's atmosphere that astronomers can use are the radio and the visible. This is mainly because other wavelengths suffer from excessive
   (a) interference.
   (b) reflection.
   (c) absorption.
   (d) refraction.
   (e) emission.
   

9. Which of the following would be the best location for an observatory on Earth (ground-based observing)?
   (a) Death Valley, California - where the altitude is below sea level.
   (b) Mauna Kea, Hawaii - where the altitude is almost 14,000 feet.
   (c) Downtown New York City.
   (d) Outside of Yellowstone National Park in rural Wyoming.
   (e) Kitt Peak, Arizona - where the altitude is almost 7,000 feet.
   

10. Which of the following best describes the changes in azimuth of sunset observed throughout the year from Iowa City?
    

    (a) The Sun sets slightly East of West in the winter, and due West in the summer.
    (b) The Sun sets slightly North of West in the winter, and slightly South of West in the summer.
    (c) The Sun sets slightly South of West in the winter, and slightly North of West in the summer.
    (d) The Sun sets in the same location throughout the year - due West.
    (e) The Sun is higher in the sky during the summer than it is in the winter.
    

11. If the Moon is observed to be in the East when the Sun is in the West, then the Moon is in what phase?
    (a) New Moon
    (b) First Quarter
    (c) Third Quarter
    (d) Waxing Gibbous
    (e) Full Moon
    

12. At different times of the year, different constellations are visible in the night sky. The astronomical reason for this is
    (a) the tilt of the Earth's axis with respect to its orbital plane.
    (b) parallax as the Earth changes its position in space.
    (c) the rotation of the Earth on its axis.
    (d) the orbital motion of the Earth around the Sun.
    (e) the motion of the Sun through the Milky Way galaxy.

13. Atoms have particular spectral lines because
    (a) light consists of waves with certain frequencies.
    (b) electrons have only certain allowed energy levels.
    (c) light waves can show the Doppler effect.
    (d) photons have only certain allowed energy levels.
    (e) the speed of light is constant.
    

14. From which of the following locations do you see the celestial equator on your horizon?
    (a) the South Pole
    (b) at a latitude of 23.5 degrees
    (c) the earth's Equator
    (d) the Tropic of Cancer
    (e) the Arctic circle
    

15. A spectrum (a plot of peak intensity versus wavelength) is made for two stars. Star A has a peak intensity at a wavelength of 300 nanometers and Star B has a peak intensity at a wavelength of 600 nanometers. Which of the following is true?
    (a) Star A is twice as hot as Star B.
    (b) Star B is hotter than Star A by a factor of 2.
    (c) Star A is four times as hot as Star B.
    (c) The two stars have the same temperature.
    (d) There is not enough information to determine which star is hotter

Answers: 1(e), 2(e), 3(b), 4(c), 5(d), 6(d), 7(e), 8(c), 9(b), 10(c), 11(e), 12(d),
13(b), 14(a), 15 (a)