Week 8

1. What evidence helps us determine the age of the earth?
   

   a.  Dating the age of rocks from the moon.
   b.  Dating of rocks from the earth.
   c.  Dating meteorites from the asteroid belt.
   d. All of the above.
   

2. The planets all lie in nearly the same plane resulting in a disk-like structure for the solar system.  This structure is believed to exist because
   

   a.  the bipolar flow from the young Sun cleared all material out of the nebula except that in the disk
   b.  Jupiter's gravity was great enough to pull all the other planets to the plane of its orbit.
   c.  low-mass planetesimals settled into the plane due to collisions.
   d.  as the original solar nebula contracted, the gas and dust fell into a disk before planets formed.
   

3. From what we know about planets outside of our solar system...
   

   a.  Planets are rare and our solar system is an exception.
   b.  Planets are undetectable outside of our solar system.
   c.  Planets are probably common, numbering in the billions in our galaxy alone.
   d.  Only the lowest mass stars have planets.
   

4. The larger objects in our solar system developed more slowly than the smaller objects because..
   

   a.  Higher speed.
   b.  Adding more material took more time.
   c.  Gas accumulated slowly, so it took more time.
   d.  Small objects lost materia during collisions.
   

5. Once a terrestrial planet had formed from a large number of planetesimals, additional thermal energy from ________ could have melted it and allowed it to differentiate into a dense metallic core and a lower density crust.
   

   a.  the Sun
   b.  tidal forces between planet and the Sun
   c.  volcanic eruptions
   d.  radioactive decay of elements
   

6. Protoplanets of the Jovian planets could have grown very hot from
   

   a.  heat from the Sun.
   b.  radioactivity of light elements such as hydrogen and helium.
   c.  the in-fall of gaseous material at high velocity (gravitational energy)
   d.  tidal forces due to the Sun.
   

7. The icy planetesimals that should have formed in the outer part of the solar system but did not participate in planet-building are presently
   

   a.  far outside the orbits of the Jovian planets, and we occasionally see one in the form of a comet when it enters the inner solar system.
   b.  scattered throughout the solar system, but we can only see them when they get near to the Earth.
   c.  in a comet belt between the planets Uranus and Neptune.
   d.  Nonsense - icy planetesimals could not have formed anywhere in the solar system becauseof the Sun's intense radiation.
   

8. The dominant mechanism for clearing the dust and gas from the solar system was...
   

   a.  impacts by planetesimals.
   b.  the Sun's magnetic field, which directed the dust and gas away from the solar system.
   c.  the solar wind - the Sun's charged particles pushed the dust and gas away.
   d.  radiation pressure - photons from the Sun pushed the dust and gas away.
   

9. Moons of the Jovian planets are probably...
   

   a.  a combination of natural satellites and captured planetoids.
   b.  composed of light elements such as hydrogen and helium.
   c.  made of debris from passing comets
   d.  displaced asteroids.
   

10. The rocky planetesimals that we now call asteroids did not form a planet between Mars and Jupiter because
    

    a.  the asteroids are moving too fast and chaotically in their orbits to stick and form a planet
    b.  the gravitational influence of Mars prevents the asteroids from combining into a planet.
    c.  the gravitational influence of Jupiter prevents the asteroids from combining into a planet.
    d.  the gravitational influence of Saturn prevents the asteroids from combining into a planet.
    

11. What was the primary role of dust in the formation of the solar system?
    

    a.  Dust veiled the process by which our solar system formed.
    b.  Dust acted as condensation nuclei; platforms to which other particles could attach and form larger particles of matter.
    c.  The Sun formed from a vast spinning cloud consisting mainly of dust.
    d.  Dust provided the radioactive elements that initially heated the Sun.
    

12. What causes a meteor shower?
    

    a. Earth encounters a debris trail left over from human space programs.
    b. Earth intercepts a stray swarm of asteroids.
    c. Earth crosses the orbit of a comet, and this orbit is littered with debris.
    d. A small constellation of dying stars disintegrates and leaves a debris trail in Earth orbit.
    

13. Comets are mostly made of...
    

    a. silica and carbonaceous material.
    b. metallic dust particles.
    c. methane, ammonia, and water ices.
    d. carbon, nitrogen, oxygen.
    

14. What is a possible cause for a nebula to contract into a star?
    

    a.  Angular momentum.
    b.  Magnetism.
    c.  The Big Bang.
    d.  A supernova.
    

15. Which of the following is (are) consistent with the hypothesis that small objects such as asteroids formed before planets rather than from destruction of early planets?
    

    a. Photographs of asteroids show very few impact craters over most of their surface.
    b. Radiometric age dating of asteroid pieces that have landed on Earth indicate a uniform age of about 4.6 billion years.
    c. The great majority of asteroids spin very slowly, if at all.
    d. All of the above.
    

16. What is currently the most popular theory of the origin of Earth's moon?
    

    a.  Independent dual accretion of two bodies.
    b.  Captured planetoid from elsewhere in the solar system.
    c.  Impact debris of a double planet collision.
    d.  Spin off from a fast rotating Earth.
    

17. How can a massive planet form very close to a parent star?
    

    a.  If dust shrouds a star, blocks light, and lowers the temperature in the solar nebula, massive planets can form close to a star.
    b.  For solar nebulae that consist mostly of heavy metals, massive planets can form close to the star and still contain little hydrogen or helium.
    c.  Computer simulations indicate that stars can capture massive planets created elsewhere in the galaxy, with about the same frequency as that observed so far.
    d.  Nonsense - the composition of massive planets must be mostly hydrogen and helium, so they must form far from the star and somehow migrate inward to where we now see them.

18. Which planet has the highest overall density?
    

    a. Mercury
    b. Venus
    c. Earth
    d. Mars
    

19. How many moons orbit Mars?
    

    a. 0
    b. 1
    c. 2
    d. 3
    

20. What organization was formed in 1919 to officially designate things like names of celestial bodies, constellations, and what constitutes the planets within our solar system (they demoted Pluto)?
    

    a. IAU
    b. ASA
    c. IMF
    d. SOB