Across
- 3. nuclear fusion in the stars core produces helium from hydrogen
- 5. group of stars
- 10. how the universe formed
- 11. Matter that we can’t see but know exists
- 12. tens of thousands of stars that are held tightly together by gravity
- 13. our galaxy
- 15. galaxies that are not spiral or elliptical
Down
- 1. galaxy that only contains a few million to few billion stars
- 2. hypothetical form of energy
- 4. egg shaped rotation galaxy
- 6. change in frequency of a wave relative to an observer moving in relationship to the source of the wave
- 7. the study of the universe
- 8. two stars orbiting each other
- 9. biggest group of stars
- 14. so dense that light cannot escape gravity