1. The Solar System Chapter 23.1

2. The Solar System 99.85% of the mass of our solar system is contained in the Sun 99.85% of the mass of our solar system is contained in the Sun 8 planets: 8 planets: Mercury Mercury Venus Venus Earth Earth Mars Mars Jupiter Jupiter Saturn Saturn Uranus Uranus Neptune Neptune (Pluto) (Pluto)

3. The Planets All planets travel in an elliptical orbit and travel in the same direction around the Sun All planets travel in an elliptical orbit and travel in the same direction around the Sun The orbital planes of seven planets lie within 3 degrees of the plane of the Sun’s equator The orbital planes of seven planets lie within 3 degrees of the plane of the Sun’s equator Mercury’s orbit is inclined 7 degrees Mercury’s orbit is inclined 7 degrees Pluto’s orbit is inclined 17 degrees Pluto’s orbit is inclined 17 degrees

4. The Planets: An Overview Terrestrial (“Earth-like”) planets: Terrestrial (“Earth-like”) planets: Mercury Mercury Venus Venus Earth Earth Mars Mars Jovian (“Jupiter-like”): Jovian (“Jupiter-like”): Jupiter Jupiter Saturn Saturn Uranus Uranus Neptune Neptune

5. Terrestrial vs. Jovian Which group of planets are bigger? Which group of planets are bigger? Planet Diameter (km) Mercury4,878 Venus12,104 Earth12,756 Mars6,794 Jupiter143,884 Saturn120,536 Uranus51,118 Neptune50,530

6. Terrestrial vs. Jovian Which group of planets has a faster period of rotation? Which group of planets has a faster period of rotation? Planet Period of Rotation Mercury 59 days Venus 244 days Earth 23 hrs 56 mins Mars 24 hrs 37 mins Jupiter 9 hrs 50 mins Saturn 10 hrs 14 mins Uranus 17 hrs 14 mins Neptune 16 hrs 3 mins

7. Terrestrial vs. Jovian Which group of planets has a greater density? Which group of planets has a greater density? Planet Density (g/cm 3 ) Mercury5.4 Venus5.2 Earth5.5 Mars3.9 Jupiter1.3 Saturn0.7 Uranus1.2 Neptune1.7

8. Terrestrial vs. Jovian Terrestrial planets consist mostly of rocky and metallic substances Terrestrial planets consist mostly of rocky and metallic substances Jovian planets consist of large amounts of gases (hydrogen and helium) and ices (mostly water, ammonia, and methane) Jovian planets consist of large amounts of gases (hydrogen and helium) and ices (mostly water, ammonia, and methane)

9. General Trends What happens to the planets’ period of revolution as they get farther away from the Sun? What happens to the planets’ period of revolution as they get farther away from the Sun? Planet Period of Revolution Mercury 88 days Venus 225 days Earth 365 days Mars 687 days Jupiter 12 years Saturn 29.5 years Uranus 84 years Neptune 165 years

10. General Trends What happens to the planets’ orbital velocity as they get farther away from the Sun? What happens to the planets’ orbital velocity as they get farther away from the Sun? Planet Orbital Velocity (km/s) Mercury47.5 Venus35.0 Earth29.8 Mars24.1 Jupiter13.1 Saturn9.6 Uranus6.8 Neptune5.3

11. Atmosphere of the Planets Planet’s ability to retain an atmosphere depends on its mass and temperature Planet’s ability to retain an atmosphere depends on its mass and temperature A gas molecule can escape from a planet if it reaches a speed known as the escape velocity A gas molecule can escape from a planet if it reaches a speed known as the escape velocity A planet that has a lot of mass (and therefore gravity) will hold on to the gas molecules A planet that has a lot of mass (and therefore gravity) will hold on to the gas molecules A planet that is cold will have slow moving gas molecules A planet that is cold will have slow moving gas molecules

12. Nebular Theory A cloud of dust and gas in space is called a nebula A cloud of dust and gas in space is called a nebula A nebula is made of 92% hydrogen, 7% helium, and less than 1% heavier elements A nebula is made of 92% hydrogen, 7% helium, and less than 1% heavier elements Nebular Theory: the Sun and planets formed from a rotating disk of dust and gases Nebular Theory: the Sun and planets formed from a rotating disk of dust and gases

13. Planetesimals Solid bits of matter began to collide and clump together through a process of accretion Solid bits of matter began to collide and clump together through a process of accretion These small, irregularly shaped bodies are called planetesimals These small, irregularly shaped bodies are called planetesimals

14. Formation of Our Solar System Terrestrial planets are dense and solid because only metals and minerals were solid so close to the Sun during formation Terrestrial planets are dense and solid because only metals and minerals were solid so close to the Sun during formation Jovian planets became gas giants because they formed from the accumulation of large quantities of ice and grew large enough to capture light gases Jovian planets became gas giants because they formed from the accumulation of large quantities of ice and grew large enough to capture light gases