 The Sun  The Planets (Inner and Outer)  Satellites  Asteroids and Comets

 Ball of gas whose heat is generated by nuclear fusion reactions in its core.

 Center of Solar System – center of mass  Gravitational force holds all other bodies in their orbital pattern.  Made of Hydrogen (71%) and Helium (~27%) and other elements (Carbon, Iron, Uranium, etc)

the common center of mass around which two or more bodies revolve; the point around which they both orbit each other

 All planets orbit counterclockwise around the Sun  Two types: Inner and Outer planets

 Mercury, Venus, Earth, and Mars  Also called terrestrial planets because they are “rocky”  Little or no atmosphere  Composed mainly of silicon and oxygen. Also, aluminum, magnesium, sulfur, and iron

 Silicon is outnumbered by hydrogen (25,000 to 1) but because it is warm near the Inner Planets the hydrogen, methane, ammonia cannot condense  Remember Step 2 in Solar Nebula hypothesis?  If only “rocky” or material condenses the planet will be “rocky”

 Jupiter, Saturn, Uranus, and Neptune  Also called “Gas Giants”  Most have deep, hydrogen-rich atmospheres  Made of water vapor, carbon dioxide, frozen ammonia, and/or frozen methane

 Have no true “surface”  Their atmospheres thicken with depth so there is a transition from gas to somewhat liquid materials on what would be the “surface”  Possible that the center is solid if differentiation is happening just as it did on Earth.

 Satellite: a body that orbits a planet  Over 200 total moons/satellites have been recognized thus far.  More details about specific moons later on!

 Asteroids: rocky bodies with diameters that range from a few meters up to 1000 km (1/10 size of Earth!)  Comets: icy bodies about 10 km or less.

 Asteroids: originate in the Asteroid belt (large orbital belt in between Mars and Jupiter)  Comets: originate either in the Oort cloud (region that surrounds Solar System-full of frozen material) OR in the Kuiper belt (region just beyond Neptune)

 What element is most prominent in the Sun?  What planets are the inner or “terrestrial” planets?  What planets are the outer or “Gas Giant” planets?  What is another word for satellite?  Where do comets originate? Where do asteroids originate?