1. Learning target: I will be able to distinguish the difference between the parts of our solar system Warm –Up Write the planets in order

2. Introduction to the solar system
Chapter 4.1

3. Changing views of our solar system
Earth at the center of the universe
Everything was in spheres rotating around Earth
~ 150 AD Ptolemy published a model of the solar system

4. Changing views of our solar system
The Sun at the center of the universe
~1500 years after Ptolemy
Copernicus proposed Sun in the center of the universe
Model wasn’t published till he died
Wasn’t until Galileo created his telescope
Proposed the planets orbit the sun like the moons of Jupiter orbited the planet

5. Planets and their motion
Solar System: the sun and all the objects that are held together by the suns gravity
8 planets, 5 dwarf planets, over 165 moons, many asteroids and other objects

6. What is and is not a planet
Pluto controversy
Planet was discovered in 1930 later to find that it wasn’t like the other 8 planets
They were using older telescopes so they didn’t have the ability to see Pluto and its moon as two separate things
Astronomers also discovered many objects like Pluto ( icy and rocky)
They had to decide…. What makes a planet

7. What makes a planet a planet
A planet must be the following
Orbit a star
Be big enough that its own gravity causes it to be round
Be small enough it isn’t a star itself
Have cleared that area of its orbit
Dwarf Planet
If the first three listed above are true

8. The size and shape of orbits
The farther from the sun the greater the one planets orbit is to the next planet

9. The size and shape of orbits
Planets are held in their orbits by gravity
Gravity depends on the mass of the object and how far apart the objects are from each other

10. Extrasolar planets
Since early 1900’s we have discovered other solar systems
exoplanets
When a planet orbits a star other than our Sun
Signs
Slight motion in the star due to the planets gravitation pull
Partial dimming of star’s light as the planet passes in front