IAU definition of planet

High school (ages 12+)
Space & Astronomy

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/iau-definition-of-planet

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the number of officially defined planets in our solar system?8
2. What is the year of formal IAU planet definition?2006
3. Why does Pluto not count as a planet?Pluto is not a planet because it shares its orbit with many other small bodies in the Kuiper Belt, so it hasn't cleared its neighborhood.
4. What does "cleared the neighborhood" mean?"Cleared the neighborhood" means the planet has taken most of the other small objects in its orbit, either by pulling them together or pushing them away, so it is the main thing there.

Trans-Neptunian Object (TNO): Any celestial body orbiting the Sun beyond the orbit of Neptune.
Hydrostatic Equilibrium: The state where a celestial body's shape is determined by the balance between gravity and internal pressure.
Comparative Planetology: The study of planets by comparing and contrasting their various features and characteristics.