Before the 20th century, what was the primary method for distinguishing planets from stars?

Planets were distinguished from stars based on their movement against the background of stars.

Why did the discovery of objects like Ceres, Pallas, Juno, and Vesta lead to a reclassification of celestial bodies in the 19th century?

The discovery of many objects in the asteroid belt led to a need to differentiate these smaller bodies from the larger planets, resulting in the term 'asteroid'.

What event in 2005 reignited the debate about the definition of a planet?

The discovery of Eris, a distant icy object slightly larger than Pluto, reignited the debate.

According to the IAU's definition, what are the three criteria a celestial body must meet to be classified as a planet?

It must orbit the sun, have sufficient mass to achieve hydrostatic equilibrium (a nearly round shape), and have cleared its orbit of other objects.

What are the four criteria that define a dwarf planet according to the IAU?

It must orbit the sun, have sufficient mass to achieve hydrostatic equilibrium (a nearly round shape), has not cleared its orbit of other objects, and is not a moon.

Is Pluto a Planet?

10th GradeScience55 min

Learning Objective

I can argue whether Pluto should be classified as a planet using evidence and reasoning.

Lesson Flow

Watch Video

8 min

What Is A Planet?

NASA Science

Guided Notes

11 min

Key concepts students will learn:

•
The ancient Greeks called objects that moved against the background of stars 'planetes', meaning wanderer.
•
According to the IAU, a planet must orbit the sun, have sufficient mass to be nearly round, and clear its neighborhood of other objects.
•
Pluto is considered a dwarf planet because it has not cleared its neighborhood and resides in the Kuiper Belt.

Practice

17 min

12 questions • Multiple choice & Short answer

Exit Ticket

5 min

“Using evidence from the video, argue whether or not Pluto should be classified as a planet. Support your argument with at least two specific reasons.”

Teacher Guide

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Answer keys for all questions
Differentiation strategies
Extension activities
Printable student handouts

Is Pluto a Planet?

Learning Objective

Lesson Flow

Watch Video

Guided Notes

Practice

Exit Ticket

Teacher Guide

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