solar system. the sun, planets, their moons and a variety of smaller objects. * smaller objects...
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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?
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