Solar System

The Sun, planets, their moons

and a variety of smaller objects.

* Smaller objects include comets, asteroids and

meteoroids.

What makes up the solar system?

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?

Johannes Kepler

Laws of Planetary Motion

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

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?

Kepler’s Third LawThe greater the distance a planet is from the Sun, the longer it takes to complete a period

(full revolution around the Sun- “year”).

Size of Planets Compared to the Sun

Size of Planets Compared to Each Other

Historical Models of Solar SystemGeocentric Model

“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

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.

Exit Slip: Solar System1. 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?