1. A Journey to Our Planetary Neighbors
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 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