The Earth, a Planet

Guiding Question:  If the earth is a planet, what makes a planet a planet?

Objective:  Students will be able to identify what makes a planet a planet.


  • Copies of blank Venn Diagram, or large group Venn Diagram on Smartboard

Vocabulary:  Planet, Sun, Earth, Asteroid, Meteoroid, Comet, Moon, star


Make copies of the blank Venn Diagram

Activity - Prior Knowledge:

  1. Have the students complete a Quickwrite by completing this sentence:  "A planet is...
  2. Tell the students that you are going to look at what a planet is...and is not...
  3. As a class, or in small groups, have students complete a Venn Diagram that compares and contrasts the earth, moon and sun...and their relationships.

Activity - New Knowledge:

  1. Review completed Venn diagram with the class
  2. Divide the students into groups of 2-4.
  3. Direct each student group to "research" what makes a planet a planet by exploring the characteristics of various space objects (asteroids, meteoroids, comets, dwarf planets, planets, moons, star).


  1. Upon completion of the research, give each student a pad of post-its
  2. Have the student groups write one characteristic of what a planet is on the post-its (one characteristic per post-it)...until they run out of characteristics
  3. Have a representative from each student group stick the post-its to a wall/whiteboard
  4. Have a student from each group read to the large group what was written on each of their group's post-its
  5. Choose several students to "categorize" the post-its by moving them into groups on the wall
  6. As a class, discuss the groupings...and develop a definition of a planet using the "grouped" post-its on the wall as a reference




Exit Slip:  "What makes a planet a planet?"

Extension:   Watch the short video What About Pluto, then pose this question to the students:  "What does Pluto have in common with the planets...and what is different?"