Read my Week 8 instructor notes for an introduction to this week's topic.


  • Go to the following page to find information concerning what we know about planets outside our solar system, aka extrasolar planets.   This information may be particularly useful for the week 8 quiz.

  • Go to the following page to see evidence supporting the theory of planet formation:  extrasolar planet formation evidence

  • Click here for more information about asteroids & comets.

  • Click here for interesting and fun stories about Leonid showers and storms of the past, including the 1833 "storm" when thousands per minute occurred. 

  • For a good summary of the Tunguska explosion event in Siberia in 1908, go to the following links:

  • For a summary of Earth craters, with images, go to the following link:

  • Go to the following link to read about the news of a mass extinction that occurred about 250 million years ago (even bigger than the Chicxulub event):

  • Click here for a good description of the major implications of finding Sedna, a planetoid orbiting far beyond Neptune's orbit - also beyond the Kuiper belt.

  • Go to this NASA page for the official definitions (as of 2007) of Planets, Dwarf Planets, and Small Solar System Bodies:
    This whole definition gig dragged out over half a decade; some astronomers would agree if you think it's a little silly.  All of the designated Dwarf Planets to date (September 2007) enjoy dual classification:  Dwarf Planet as well as Small Solar System Body.  For example, Pluto is a DP as well as a Kuiper Belt Object (KBO), which is one of the Small Solar System Body categories.  Why not simply call it a KBO?  One other KBO now enjoys DP status, as does the asteroid Ceres.  Can you figure out the primary distinction between small things and dwarf planets?  And why would our Moon, which is larger and more massive than Pluto, not qualify for Dwarf Planet status?  Find the answers at this URL and ponder the value of arbitrary definitions, as well as work by committees.

2.  Respond with written answers to the week 8 discussion questions.   I'll take questions about these during class time.   Assess your responses by comparing with my week 8 DQ responses on this web-site, as instructed on my responses page.  Turn these in the first day of week 9.

3.  Print out the week 8 quiz and circle your answer choice for each question.  I'll take questions about these during class time   Turn these in the first day of week 9.