Chapter 25

2. expresses the rate at which the universe is expanding.
3. early stage in the formation of a star
6. exploding star
9. grouping of stars
12. the largest objects in the Universe held together by gravity.
15. band of stars
16. what stars like the Sun become after they have exhausted their nuclear fuel
17. spherical, compact objects that are about the size of a large city but contain more mass than the sun

1. any of a class of extremely dense, compact stars thought to be composed primarily of neutrons.
4. a giant explosion at the end of a stars life
5. a place in space where gravity pulls so much that even light can not get out.
7. any of the systems of stars and interstellar matter that make up the universe.
8. also called a H-R diagram
10. pair of stars
11. how astronomers explain the way the universe began.
13. distance light travels in a year
14. a dying star