1. Composition of Objects in Space Notes 4.4 Composition = the types of materials and how they are arranged in an object Objects to be looked at: terrestrial planets, gaseous outer planets, Oort Cloud, Kuiper (ky-per) Belt, asteroids, meteors, and comets.

2. Terrestrial Planets Rocky, with metal cores and solid surfaces. “Close” to the sun compared to gaseous planets** **Not as close to the sun as other terrestrial planets are to their star in other solar systems

3. Gaseous Outer Planets Jupiter, Saturn, Uranus, Neptune Have no solid surfaces  Hydrogen and Helium We can not yet image gas planets around other stars (in other solar systems)

4. Oort Cloud This is only a working hypothesis (by Jan Oort, 1950) Says that there is a vast cloud at the outer reaches of our solar system 50,000 AU away Is where long-period comets come from

5. Kuiper Belt Past Neptune A disk-shaped area with many icy bodies that may sometimes cross Neptune’s orbit This either flings them out of the solar system or in towards inner planets!

6. Asteroids Rock and metal objects They do not “stick” together to form a planet because of Jupiter’s gravity That causes them to bounce off and break each other apart Located between Mars and Jupiter

7. Meteors = “Shooting Star” When dust and icy chunks enter earth’s atmosphere, heat up, glow, and then burn down Becomes a meteorite when it makes it to the surface of the Earth

8. Comets Are further from the sun than asteroids. Are balls of dust and ice When their orbit passes close enough to the sun, that makes the vapor trail we see.