Astronomy

4. our solar system that forms a tiny part of the galaxy
7. a theory that states that the universe could go on expanding and everything would eventually fade away
8. a theory about a violent explosion that began 15,000 million years ago
10. very large and can contain up to one million stars
13. a bright middle and two or more curved arms of stars
14. vary in shape from round to oval, and contain many old, red stars
15. a pulling force

1. the name used to describe the collection of matter.
2. a theory that states that the universe expands and shrinks, and that the universe works like a heart
3. found in areas of space that are rich in gas and dust
5. the distance light travels in one year
6. tiny particles that make up virtually everything in the universe
9. cloud of stars with no definitive shape
11. has a central bar of stars with an arm at each end
12. billions of stars gathered together in huge collections