1. Solar System

2. The Sun, planets, their moons and a variety of smaller objects. * Smaller objects include comets, asteroids and meteoroids. What makes up the solar system?

3. Scientist believe it formed about 4.6 billions years ago from a cloud of interstellar gas (hydrogen, helium, rock, ice and other materials) that collapsed and formed the Sun. Leftovers then came together to form the planets. How did the solar system form?

4. Johannes Kepler Laws of Planetary Motion

5. Planetary orbits are elliptical shaped (nearly circular). **Planets revolve around the Sun in the same direction (counterclockwise) but not the same speed. Kepler’s First Law

6. Kepler’s Second Law When a planet’s orbit is closer to the Sun, the planet’s speed increases. When it is farther away, its speed decreases. QUESTION: Why do you think this is so?

7. Kepler’s Third Law The greater the distance a planet is from the Sun, the longer it takes to complete a period (full revolution around the Sun- “year”).

8. Size of Planets Compared to the Sun

9. Size of Planets Compared to Each Other

10. Historical Models of Solar System “geo” means Earth “centric” means centered Early astronomers believed that the Earth was center of solar system and everything revolved around it. “helio” means Sun “centric” means centered The belief that the Sun is the center of the solar system and everything revolves around it. Heliocentric Model

11. Compare Planet Sizes Use your text book (pg.52-65)A, the link above and your thermometer handout to research the following information for each planet: Diameter Distance from the Sun Period of revolution Average temperature Fill in your Planetary Data chart.

12. Exit Slip: Solar System 1. List and explain Kepler’s Laws (all three!) 2.How do scientists believe the Solar System was formed? 3.Compare and contrast the two models of the Solar System. 4.Why do you think people in the ancient times believed in the geocentric model?