Solar System Updates, Spring 2009

      

Changing Science

One of the beautiful things about science is that its concepts and theories change as new discoveries are made. This can, however, pose a challenge for keeping paper textbooks current. If you currently use the Our Solar System module, here are notes about changes in the prevailing definition of a planet and how these affect the book in your classroom.

 

Pluto

  • Pluto was discovered in 1930 and designated as the ninth planet. As observation and analysis methods were refined, each new piece of information about Pluto set it apart as an oddball compared with other planets—much smaller, with a more elliptical orbit. With the discovery of other objects similar to Pluto, the decision about what to call a planet and what not to call a planet was getting messy.

 

  • On August 25, 2006, the International Astronomical Union (IAU) created a definition of a planet which excluded Pluto and similar bodies. The designation of Pluto was changed from planet to dwarf planet. Here is one good place to read about the change: 
         

http://solarsystem.nasa.gov/planets/profile.cfm?Object=Dwarf&Display=OverviewLong

 

  • Under the new definitions there are now eight planets instead of nine. This change affects two of the big ideas in the Our Solar System Teacher Lesson Manual, which  should now read as:

 

  • The sun is the center of our solar system, and Earth is one of eight planets that orbit it. (Lessons 20, 21, 23)
  • Eight planets orbit around our sun. (Lessons 24, 25, 26)

 

  • Revisions of the Our Solar System Teacher Lesson Manual are underway, and will be available in an electronic version of the book by fall of 2009. In the meantime, we’ll post updates here that incorporate new information.

 

  Click here to download updated text for TBI pages 429-430

 

 

Updates for Time-dependent Data