1. Solar System
The solar system is the gravitationally bound system comprising the sun and the objects that orbit it.

2. Formation of the Solar System
The solar system formed 4.6 billion years ago
Gravitational collapse of a giant interstellar molecular cloud.
Vast majority of the system’s mass (99.86%) is in the sun, with most of the remaining mass contained in Jupiter.

3. Four inner planets “terrestrial” planets
Mercury, Venus, Earth and Mars
Composed of rock and metal

4. Four outer planets Giant planets
Much more massive than the terrestrial
Jupiter and Saturn are gas giants, mostly hydrogen and helium
Uranus and Neptune are ice giants, mostly water, ammonia and methane

5. Orbits Elliptical, but nearly circular Flat
Within a flat disc called “ecliptic”

6. Smaller Objects Asteroid belt between Mars and Jupiter
Kuiper belt beyond Neptune (ices)
Dwart planets (Pluto, Chiron, Ceres, Eris)
Solar wind. A stream of charged particles flowing outward from the sun.
Oort cloud. Source for comets. Reservoir of ices.

7. Sun
99.86% of mass of solar system (332,900 times the mass of the earth)
Mostly hydrogen and helium
Fusion of hydrogen into helium.
Main sequence star on Russell Hertzsprung
Surface temperature 5500 – 5700 K
Radiates yellow and yellow-green light

8. Inner Solar System
Four terrestrial or inner planets have dense, rocky compositions, few or no moons and no ring systems.
Venus, earth and Mars have atmospheres that generate weather
Impact craters, mountains, valleys and volcanoes

9. Asteroid belt Between Mars and Jupiter
Rock and metallic minerals with some ice
Remnants from solar system formation that failed to coalesce because of the gravity of Jupiter
Tens of thousands, perhaps millions, of objects over one kilometer in diameter.

10. Outer solar system Four outer planets or giant planets
All four giant planets have rings
Jupiter and Saturn are hydrogen and helium gaseous
Uranus and Neptune are ices of water, ammonia and methane

11. Kuiper belt Mostly ice Dwarf planets
100,000 objects with diameter greater than 50 kilometer
Pluto, Chiron (moon of Pluto)

12. Oort Cloud
Trillion icy objects
Source for comets
Move very slowly

13. Solar System in Milky Way
Milky Way is a spiral galaxy with a diameter of 100,000 light years containing about 100 billion stars (10^(11))
The sun is on one of the outer spiral arms between 25,000 and 28,000 light years from the center of the Milky Way.
Speed is 220 km/s, so it completes one revolution every million years.