Our Solar System

1. Our Solar System A Journey to Our Planetary Neighbors

2. Ideas about the night sky have changed over time… • Earth-centered model – early Greeks thought planets, Sun, Moon and stars rotated around the Earth • Modern view – • The sun is the center of our solar system • All other objects in the solar system revolve around the sun in elliptical orbits at different speeds.

3. How did our solar system form? • A nebula of gas, ice, and dust slowly formed in space, and rotated in space. • The cloud began to contract and the matter was squeezed into less space. • The cloud became dense, heated up and triggered a nuclear fusion reaction that created the sun.

4. What happened next? • All leftover matter became the planets and asteroids • The four inner planets – (Mercury, Venus, Earth, and Mars) are small and rocky with iron cores • The four outer planets – (Jupiter, Saturn, Uranus, and Neptune) are large, lightweight, and composed of gases.

5. Inner Planets • Mercury - closest to the Sun, smallest planet • Many craters and high cliffs • No true atmosphere so temperatures can range from -292 to 806° F. • It orbits the sun once every 88 days and is an average of 36 million miles from the sun.

6. Inner Planets • Venus – second from the sun and similar to the Earth in size and mass • Mostly smooth volcanic plains • Extremely dense atmosphere of clouds • Carbon dioxide gas traps solar energy resulting in temperatures between 842 to 887° F. • It is an average distance of 67 million miles from the sun and orbits every 225 days

7. Inner Planets • Earth – third planet from the Sun • More than 70 percent of surface is covered with water • Atmosphere consists of several layers, is mostly composed of nitrogen and oxygen, and protects the surface from meteors and Sun’s radiation • It is an average of 93 million miles away from the sun, and completes its orbit in 365.5 days

8. Inner Planets • Mars – fourth planet from the Sun • Called red planet because of iron oxide in rocks • Polar ice caps made of frozen carbon dioxide and water • Surface contains gullies, mountains and canyons, plains and the largest volcano in the solar system • The thin atmosphere mostly contains carbon dioxide • It is an average of 141 million miles from the Sun, and completes its orbit in 1.9 years

9. Asteroids and Other Objects in Our Solar System • Asteroids – rocks similar to that which formed the planets • Asteroid Belt – group of asteroids that orbit the Sun between the planets Mars and Jupiter

10. Comets • Comet - dust and rock particles combined with frozen water, methane, and ammonia • Halley’s comet (occurs every 76 years), Hale-Bopp (1995) • Look similar to a dirty snowball • The ice and dust vaporize as it approaches the sun • This forms a comets tail

11. Meteoroid, Meteor, and Meteorite • Meteoroid – small pieces of debris in space • Meteor – small meteoroid that burns up in Earth’s atmosphere (falling or shooting star) • Meteorite – meteoroid that strikes Earth

12. Outer Planets • Jupiter – Fifth planet from the sun and the largest in our solar system • Atmosphere mainly consists of hydrogen and helium • Surface is suspected to be composed of liquid hydrogen and helium, and may have solid core at the center • It is an average of 484 million miles from the sun and 11.8 years to complete one orbit • Has 16 moons

13. Outer Planets • Saturn – sixth planet from the Sun • Thick outer atmosphere of hydrogen, helium, ammonia, methane, and water vapor • Might have rocky core • Rings that circle around planet are composed of ice and rock particles • It is an average of 887 million miles from the Sun, and completes one orbit in 29.5 years

14. Outer Planets • Uranus – seventh planet from the sun • Atmosphere of hydrogen, helium, and methane • Rotates on its side • Contains thin, dark rings • It is an average of 1.8 billion miles from the sun, and completes one orbit in 84 years

15. Outer Planets • Neptune – eighth planet from the Sun • Atmosphere is similar to that of Uranus • Storms on Neptune reveal an active and rapidly changing atmosphere • It is an average of 2.8 billion miles from the sun, and completes its orbit every 165 years