Across
- 5. a unit of distance equal to 1000 pc or 3260 ly
- 6. the spheriodal cloud of stars at the center of most spiral galaxies
- 9. a material confined to the plane of the galaxy
- 11. objects used to map the spiral arms
- 14. variable star with a period of 12 to 24 hours
- 16. the powerful radio source located at the center of the galaxy
- 17. stars rich in atoms heavier than helium
- 18. stars that are poor in atoms heavier than helium
- 19. the rate at which a star moves across the sky
Down
- 1. a graph of orbital velocity versus radius in the disk of a galaxy
- 2. the relation between period and pulsation
- 3. orbital motion in accord with kepler's laws of planetary motion
- 4. in astronomical usage, any atom heavier than helium
- 7. the spherical region of a spiral galaxy containing a thin scattering of stars
- 8. the process by which the birth of stars compresses the surrounding gas clouds and triggers the formation of more stars
- 10. non luminous material that is detected only by its gravitational influence
- 12. a variable star with a period of 1 to 60 days
- 13. the production of elements heavier than helium by the fusion of atomic nuclei in stars and during supernovae explosions
- 15. a region of hr diagram in which stars are unstable to pulsation