Unit 1 Review: The Universe!

1. The spiral galaxy that contains our solar system
3. The force of attraction between objects
4. Irregularly shaped objects made of rock and metal that orbit the sun
6. A group of planets and other space objects the orbit a central star
7. Earth's natural satellite (the large body that orbits the planet)
10. The period of time that it takes an object to orbit another object
11. The planet famous for large rings
12. Gravity and inertia work together to keep objects in ________ around the sun
14. The current theory for the organization of our solar system with the sun in the center
17. The planet close in size to the Earth; Earth's "sister planet"
18. The only planet able to support life
20. The force that keeps an object in motion or at rest unless acted on by another force
21. _____________ planets are the smallest planets and are mostly made of rock

1. A meteoroid that has entered Earth's atmosphere and appears as a flash of light is known as a ___________.
2. These planets are the larger planets that orbit the farthest away from the sun
4. A collection of large rocks that orbit between Mars and Jupiter
5. The red planet
8. The accepted theory that explains the formation of the Universe
9. The largest planet in our solar system
13. The scientist who suggested the Earth was the center of the solar system
15. An object in space made up mostly of ice, dust, and small rock particles
16. An atmospheric gas that makes Uranus and Neptune appear blue
19. The ______________ contains everything that exists