Lesson Plan: Units of Astronomy: The Parsec Physics

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to define the parsec using trigonometry and convert between parsecs and different length units used in astronomy.


Students will be able to

  • recall that the parsec is a unit of distance,
  • recall that 1 parsec is equal to the length of the adjacent side of a right triangle if the opposite side has a length of 1 AU and the angle is equal to 1 arcsecond,
  • use the parallax method to work out the distance to astronomical objects,
  • recall the unit symbol for the parsec,
  • convert between parsecs, meters, kilometers, astronomical units, and light-years.


Students should already be familiar with

  • llight-years,
  • astronomical units,
  • arcminutes, arcseconds, and sexagesimal notation.


Students will not cover

  • standard candles.

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