Unit 6

2. planets Jupiter, Saturn, Uranus, and Neptune
4. year the distance light travels through space in one year
5. a group of stars, dust, gas, and other objects held together by gravitational forces
6. system the sun, planets, and their moons, and other objects that are gravitationally bound to the sun.
8. a chunk of burning rock traveling through earth’s atmosphere
9. law of universal gravitation a mathematical rule that tells us how strength of the force of gravity depends on mass and distance
11. an object in space made mostly out of ice and dust
13. an object that orbits the Sun but is too small to be considered a planet

1. Way galaxy the spiral galaxy to which our solar system belongs
3. unit a distance equal to 150 million kilometers, or the distance from teh Earth to the Sun
7. a meteor that passes through earth’s atmosphere and strikes the ground
9. fusion reactions which combine light elements such as hydrogen into heavier elements such as helium, releasing energy.
10. an enormous hot ball of gas held together by gravity which produces energy through nuclear fusion reactions in its core
12. a cycle of rising and falling sea levels that repeats every 12 hours
14. the repeating circular (or elliptical) path an object takes around a gravity source, such a a planet or star.