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Planetary Puzzle

  • Planétarium Rio Tinto Alcan
Students must solve two puzzles by gathering information on the planets through a series of clues provided
Photo: NASA

Tabs group


Description of the activity

Students solve two puzzles using their knowledge of planets and the solar system.


This activity aims to acquaint students with the planets in the solar system. Students must solve two puzzles by gathering information on the planets through a series of clues provided.

Equipment needed by the student

  • A copy of the Planetary Puzzle student handout.
  • A copy of the answer grid (optional).


Make the number of copies needed of the Planetary Puzzle student handout and solve the puzzles yourself for an idea of the difficulties your students might encounter. If need be, prepare suggestions of strategies for figuring out the puzzles.

Students may have trouble organizing the information they collect as they answer the clues. If so, hand out copies of the answer grid enclosed and suggest to students that they use it to jot down their answers.

Gather resources your students might use in this activity. Make sure the information is recent. For example, references before 1990 won’t contain the discoveries about Uranus and Neptune made by the Voyager 2 probe. If you must offer both recent and older resources, plan to help your students when they come across contradictory information.

Also provide some reference material on mythology (including the names of Roman and Greek gods and goddesses). Attached is a family tree of the gods from Greek and Roman mythology.


  1. Explain to students that they’ll complete an activity that tests their ability to solve problems and their knowledge of the heavenly bodies in our solar system. Tell them that this activity might prove frustrating at times but that their perseverance will pay off.

Refresher course

Important note: Pluto is no longer a planet!
In August 2006, the International Astronomical Union (IAU), at a meeting in Prague (Czechoslovakia), established for the first time a definition of what constitutes a planet. The definition, adopted by the astronomers assembled in plenary, is based on three criteria:

  • A planet is a nonluminous object in orbit around a star (the Sun, in this case);
  • A planet is massive enough to be a sphere by its own gravitational force (it is considered that bodies whose diameter is greater than approximately 800 km have this property);
  • A planet dominates the region of space of its orbit (in other words, it absorbed or expelled smaller objects cluttering its orbit).

This last criterion excludes from the list of planets Ceres, a spherical object (about 1,000 km in diameter) in the middle of the asteroid belt, as well as Pluto, in the Kuiper belt (a vast reservoir of comets). In addition to comets, a host of objects similar to Pluto are found in this remote region of the solar system, which also rotate around the Sun in orbits similar to Pluto. Recently, an object named Eris was discovered, whose diameter is greater than that of Pluto!

In Prague, astronomers also agreed to consolidate under the term “dwarf planets” objects large enough to be be spheres, but which have not “cleared the neighbourhood” around their orbits. Ceres, Pluto, Eris and many other similar objects are therefore dwarf planets. As for the smaller (non-spherical) asteroids, comets and interplanetary dust, they have been grouped under the term “small Solar System bodies.”

In this activity, Pluto is treated as a planet due to historical and mythological tradition, but students should keep in mind that it is indeed a dwarf planet, according to the new definition of the IAU.

Category of activity

  • Preparatory activity

Sub-category of activity

  • Class activity

Grade level

  • Elementary cycle three
  • Secondary cycle one
  • Secondary cycle two

Number of students per group

2 to 4


Two 60-minutes periods

Activity Sheets

Planetary Puzzle[PDF - 109.96 KB - 10 pages]

Schedules for teachers

Planetary Puzzle (teacher's copy)[PDF - 53.68 KB - 4 pages]

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