1. The Solar System
An Inventory

2. What is the Solar System?
Answer: The system of objects in the solar neighborhood (near the Sun)
What are these objects?
One Star
Nine Planets
Six Planets
Dozens of moons
Thousands of asteroids
Trillions of comets

3. The Discovered Planets
All planets through Saturn known since the ancients – all you have to do is look up to see them
Uranus discovered in 1781 by William Herschel
He wanted to name the planet “Georgium Sidus” after his king and patron, George III of England
Neptune was first seen in 1846 by Johann Galle using predictions by Urbain Jean Joseph Leverrier and John Couch Adams
Pluto was discovered in 1930 by Clyde Tombaugh at Lowell observatory

4. Size and Scale

5. Planets The first step to studying planets? Compare and contrast
What are important quantities?
You have:
A stick
A tree
A car
A house
What are the important quantities?

6. Planetary Properties

7. Density and Mass What is mass? What is density?
Mass is similar to weight, it measures how much stuff an object is made of
Example: A bowling ball and a soccer ball are about the same size, but have different masses
What is density?
Density is mass per volume. It helps to tell you what kind of stuff an object is made of
Example: A log and a tree have different masses (and sizes), but the same density because they are made of the same stuff

8. Terrestrial Planets Close to the sun Small High density
Mass
Radius
High density
Primarily rocky
Solid surface
Weak magnetic field
Few moons
No rings

9. Jovian Planets Far from the sun Large Low density
Mass
Radius
Low density
Primarily gaseous
No solid surface
Strong magnetic fields
Many moons
Many rings

10. Terrestrial Planets

11. Earth-Moon System Distance from the earth to the moon: 384,000 km
Less than the radius of the Sun (696,000 km)

12. Differentiation and Heat
A differentiated planet is not the same all the way through. A homogeneous planet is the same.
Heating a planet allows movement.
Heavier materials sink to the inside and lighter materials rise.
Sources of Heat

13. All differentiated
Interiors

14. Jovian Planets

15. Interiors

16. Planetary Rings Composition Size Jupiter Dust Small grains Saturn
Water ice
< house size
Uranus
Carbonaceous
Large paricles
Neptune
dark, unknown
unknown, small
Planetary Rings
All the “Jovian planets” have rings
These are not solid, but composed of millions of tiny particles of ice and dust
Rings have structure: gaps and spokes

17. Rings

19. Ring structure

20. What About Pluto? Pluto does not easily fit into either category
Far from the sun (jovian)
Small (terrestrial)
Neither rocky nor gaseous (icy)
One moon
No rings
It is similar is composition to some moons in the outer solar system and its orbit is similar to a group of objects called “Kuiper Belt Objects” or KBOs

21. Pluto
Only planet in our Solar System that has not been visited by a NASA (or any other) spacecraft

22. Charon
Largest of any moon in relation to the planet it orbits (1/2 the size of Pluto)
Pluto and Charon are tidally locked to each other (always show the same face)
Charon discovered in 1978 by astronomers at the US Naval Observatory