Question Sheet: Defining Planethood
- Name all the planets in our solar system.
- What makes something a planet?
- What five planets have scientists known since ancient times?
- How is Pluto different from the other planets?
- What is the Kuiper belt?
- To a dynamicist, what qualities make an object a planet?
- What are two different ways to define a planet?
- Sykes says, “Whenever we come up with an explanation for something, we as
scientists have to be ready for someone to show us that we’re wrong.” What does
- Do you think Pluto should be considered a planet? Why or why not? See science.nasa.gov/newhome/headlines/ast17feb99_1.htm (NASA) and
- Why might scientists need to have a definition of a planet? See en.wikipedia.org/wiki/Definition_of_planet(Wikipedia).
- The new definition of a planet accepted by the IAU says that a planet must
have “cleared the neighborhood around its orbit.” What does that mean? Have
Earth, Mars, and Venus cleared their orbits? See en.wikipedia.org/wiki/Definition_of_planet(Wikipedia).
- Where is the Kuiper belt located? What sorts of objects are found in the
Kuiper belt? Why are these KBOs of interest to scientists? How does the Kuiper
belt differ from the Oort cloud? See www.windows.ucar.edu/tour/link=/comets/Kuiper_belt.html and www.windows.ucar.edu/tour/link=/comets/Oort_cloud.html
(University Corporation for Atmospheric Research).
- Should astronomers by themselves get to decide whether a body in the solar
system is a planet, or should the general public also have a say? Why?
Who discovered Pluto? When did he find it? How did he find it? How was the discovery of Pluto related to the discovery of Neptune? See en.wikipedia.org/wiki/Pluto (Wikipedia) and www-groups.dcs.st-and.ac.uk/~history/HistTopics/Neptune_and_Pluto.html
(University of St Andrews).
- Write a letter to your local newspaper arguing that either (a) Pluto should
be called a planet or (b) that Pluto should not be called a planet.
- Write a paragraph or two that your science textbook might use to describe
the history and controversy surrounding Pluto.
It takes Pluto 248.54 Earth years to orbit the sun. Neptune orbits the sun in 164.88 Earth years. How many times longer does it take Pluto to orbit the sun than Neptune? Pluto was closer to the sun than Neptune was from 1979 to 1999. What percentage of Pluto’s orbital period was spent closer to the sun?