1. The Solar System
Chapter 12 Section 1
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2. Ideas About the Solar System
Earth-Centered Model: Thought the planets, Sun, Moon, and Stars were in separate spheres that rotated around the Earth.
Sun-Centered Model: Copernicus stated Moon revolved around Earth and Earth moved around the Sun.
Galileo: observed Venus going through phases like the Moon and proved it was orbiting around the Sun.
Modern View: 8 planets, Sun is 99.86% of the mass in Solar System so gravity is immense and holds all objects in their orbits.

3. How Solar System Formed
4.6 billion years ago was a fragment of gas, ice, and dust
Cloud fragment contracted into a large, tightly packed, spinning disk
Disk center so hot and dense and created the Sun from nuclear fusion (H atoms started to fuse and release energy)
Rest of material cooled enough to clump into scattered solids
Clumps collided and combined to form 8 planets

4. Motions of Planets Johannes Kepler: studied orbits of planets
Elliptical orbits: oval shaped
Sun is not directly in center of the orbits
Found planets travel at different speeds
Planets closer to sun travel faster

5. Questions What is the Sun-Centered Model?
What is the Earth-Centered Model?
Who proved planets orbited around the Sun?
Why does the Sun hold all objects in the Solar System?
In a paragraph, write about how the Solar System formed. Must be at least 5 or more sentences.
Who studied the orbits of the planets?
Why do planets travel at different speeds?

6. The inner planets
Chapter 12 Section 2
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7. Mercury Closest planet to sun, 2nd smallest
Mariner 10 – found looks just like the Earth’s moon, many craters and cliffs
Mercury may have shrunk due to weak magnetic field
Iron core
No atmosphere
Temperatures – 425°C day and -170°C night
No moons

8. Venus Similar to Earth in size and mass 2nd from the sun
Thick atmosphere of carbon dioxide
Droplets of sulfuric acid give clouds yellowish color
Craters, fault like cracks, and volcanoes
Greenhouse effect – sunlight gives off heat in atmosphere and absorbed by carbon dioxide
Temperatures – 450°C to 475°C
No moons

9. Earth Atmosphere protects life 3rd from the sun
Temperatures allow water to be solid, liquid, and gas
Only planet with known life
One large moon - Luna

10. Mars 4th from the sun Reddish-yellow from iron oxide in soil Ice caps
Channels show water once flowed
Large volcanoes and valleys – Olympus Mons
Thin atmosphere – carbon dioxide
Temperatures: -125°C to 35°C
Huge dust storms
Two small, irregular shaped moons – Phobos and Deimos

11. Questions
What is the order of the inner planets from closest to farthest from the sun?
Why do you think Mercury’s temperature changes so much from night to day?
What causes the yellowish clouds to form on Venus?
What is the greenhouse effect?
Which planet is the only to have known life exist?
What is the Earth’s moon called?
Why is Mars a reddish-yellow color?
Which planet has the largest volcano? What is it called?

12. Jupiter Fifth planet from the sun Largest planet
Voyager revealed Jupiter has faint dust rings
Made of mostly hydrogen and helium, with some ammonia, methane, and water vapor
Middle of Jupiter, atmosphere is liquid hydrogen and helium and below a rocky core
Colorful clouds of white, red, tan, and brown
Great Red Spot – continuous storm of swirling, high-pressure gas
Moons (satellites) – at least 63 orbit Jupiter

13. Jupiter’s Moons
Io – most volcanically active object in solar system, sulfur gives it a reddish, orange color, thin atmosphere of sulfur dioxide
Europa – rocky interior with 5km thick crust of ice, many cracks, 50km deep ocean may exist under the ice, thin oxygen atmosphere
Ganymede – heavily cratered covered with icy grooves, rocky interior surrounding molten iron core, thin oxygen atmosphere
Callisto – heavily cratered with mix of ice and rock, rocky core, thin atmosphere of carbon dioxide

14. Saturn Sixth planet from sun
Second largest planet, but lowest density and gaseous
Thick outer atmosphere of hydrogen and helium with ammonia, methane, and water vapor, deeper in atmosphere becomes a liquid and then below a small, rocky core
Rings – the large ring has thousands of thin ringlets made of ice and rock particles that vary in size
Moons (satellites) - at least 47 orbit Saturn, gravity holds them in the orbit
Titan – largest moon, larger than Mercury, thick atmosphere of nitrogen, argon, and methane

15. Uranus Seventh planet from the sun Large and gaseous, 27 moons
11 thin, dark rings at equator
Largest moon, Titania, heavily cratered, deep valleys
Atmosphere – hydrogen, helium, and methane
Methane gives planet bluish-green color because absorbs red and yellow light and clouds reflect green and blue
Few cloud bands and storms visible
Made of ice and rock
Uranus’ axis of rotation is tipped on its side

16. Neptune 8th planet from sun Large, gas planet with rings
Sometimes farther from sun than Pluto
Methane atmosphere gives blue-green color
Dark colored storms in atmosphere
At least 13 moons
Rocky core
Made of rock and various ices
Thin atmosphere of nitrogen

17. Dwarf Planets
Ceres – located in asteroid belt, orbits the sun every 4.6 years, 940 km diameter
Pluto – 2300 km diameter, 248 years to orbit sun, solid icy-rock surface, three moons
Eris – 2,400 km diameter, 557 years to orbit sun, one moon

18. What is a planet? Orbits around the Sun
Has enough mass for its gravity to overcome forces so that it keeps its round shape
Has cleared the neighborhood around its orbit

19. Questions What is the Great Red Spot on Jupiter?
What are the four largest moons of Jupiter?
What are Saturn’s rings made of?
What is Saturn’s largest moon? Describe it.
Why does Uranus have a bluish-green color?
Why is Uranus different from other planets?
What gives Neptune its blue-green color?
What are the dwarf planets?
What are the three criteria for an object to be a planet?