14 Chapter 14 – Why isn’t Pluto a planet?
OpenStax Astronomy Chapter 12: Rings, Moons, and Pluto
Dwarf Planets
I.
A. A planet orbits the and:
1. Has enough to pulls itself into a shape
2. around its of other planetesimals and
B. Dwarf planets are large that to their orbit, and some are
1. officially recognized dwarf planets
2. of additional have been suggested
C. dwarf planets in the beyond Neptune’s orbit:
D. is in the main between Mars and Jupiter:
II.
A. Pluto and , Charon, sometimes called a “double planet” system
1. Has , including Charon
B. other Objects
1. , tilted
2. Made of with a little material
C. Thin is unique
III. Other
A. : most , to Pluto
1. than Pluto
2. atmosphere
3. : Dysnomia
B. : shape
1. Fastest (4 hours)
2. moons
3. system
C. : second
1. No
D. : Used to be classified as the largest
1. About a of the total of the
2. Enough self-gravity to be , unlike other asteroids
3. ice mantle, core
Moons of the Giant Planets
Section 12.2 (Io and Europa), Section 12.3 (Titan) & Section 12.5 (Enceladus)
IV. Major (of about total)
A. planets have several , as big as Earth’s
B. Some moons are
1. Internal heat from stretch of
2. features
C. moons are active, but fully
Which of the following can be used as an indicator of the age of a moon’s surface?
D. All of the above
V. : Active moon of
A. Most active in the Solar System
1. from tidal stresses with Jupiter
2. Huge , mountains and calderas
B. , very young surface
C. Colored by and sulfur compounds, bright patches may be sulfur dioxide
VI. : Active Moon of
A. Mostly
B. Young surface:
C. (cold volcanism): “magma” is crystals
1. Feeds Saturn’s
VII. : Possibly Active Moon of
A. Surface looks like of ice that appear to have
B. ocean just under surface
1. One of best places to look for – liquid water, heat, and organic materials
VIII. : Possibly Active Moon of
A. than Mercury
B. Half water and half
C. Thick, dense, -rich
D. in atmosphere and , even rain
E. Icy “rocks” and soil with compounds
1. Good place to search for
You discover a new moon of Jupiter. It orbits very far from the planet, but it has many volcanoes. Is this a surprise? Why?
Tutorial Activities
Pluto
“Elementary Astronomy Worksheet Handout 16: Small Solar System Bodies” (modified by Kaisa E. Young) by Catherine Whiting via OER Commons, licensed under CC BY 4.0, https://oercommons.org/courses/elementary-astronomy-worksheets
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2. In 2006 the International Astronomical Union made the decision to ”demote” Pluto to a new category
of Dwarf Planet. Discuss with your group whether you agree with this decision or not. What led
astronomers to make this controversial decision?
Comparing Saturn’s Moons
Look at the pictures of four of Saturn’s moons and answer the following questions.
Figure 1: Mimas (NASA/JPL/Space Science Institute), Titan (Justin Cowart), Enceladus (NASA/JPL/Space Science Institute), Dione (NASA) All images are public domain via Wikimedia Commons, modified by Kaisa E. Young.
1. Rank the moons from most cratered to least cratered.
2. Based on you observations of the pictures, rank the moons from oldest to youngest surface.
3. Do you see any evidence for any geologic activity? If so, what?
4. Do any of the moons look like they have current geologic activity?
| Moon | Density (g/cm3) |
| Mimas | 1.15 |
| Enceladus | 1.61 |
| Dione | 1.50 |
| Titan | 1.88 |
| Earth’s moon | 3.34 |
| Common Materials | Density (g/cm3) |
| Ice | 0.9 |
| Water | 1.0 |
| Rock | 3.0 |
| Iron | 7.8 |
5. Based on the information in the tables above, what do you think each moon is made of? Moons may be made of more than one material.
6. Based on your answers to number 5, would you expect geologic activity to involve molten rock (lava) or molten ice (water) on these moons?
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