What Is a Planet? Teacher Sheet

What Is a Planet? Teacher Sheet By NASA, ESA and G. Bacon (STScI) [Public domain], via Wikimedia Commons


Students may have wondered how scientists classify an object in space as a planet, a dwarf planet, a comet, or some other kind of space object. They can use the What Is a Planet? slideshow on the Is Pluto a Planet? student esheet to learn more about objects in space. Here are answers to the questions your students should answer about the slideshow.

What is a Planet?

According to the International Astronomical Union (IAU), what are the characteristics of a planet?
The characteristics of a planet are that it (a) is in orbit around the sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium [nearly round] shape, and (c) has cleared the neighborhood around its orbit.

What are some examples of planets?
Some examples of planets include Earth, Mars, Jupiter, etc.

According to the IAU, what are the characteristics of a dwarf planet?
A dwarf planet is an object in orbit around the sun that is large enough (massive enough) to have its own gravity pull itself into a round [or nearly round] shape.

What are some examples of dwarf planets?
Examples of dwarf planets include Pluto, Ceres, Eris, Haumea, and Makemake.

Why might it be useful to define the characteristics of a planet or a dwarf planet?
Answers may vary. Encourage students to explain their answers.

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