Across
- 4. pulsate in brightness because of expansion
- 7. typically made up of older red stars.
- 9. have periods of pulsating 1.5 and 1.2 days.
- 11. disk and arms have small amounts of heavy elements.
- 12. any of the very large groups of stars.
Down
- 1. occupy the clusters of most galaxies.
- 2. spiral regions of alternating density.
- 3. regions of stars that extend from the center of the galaxy and turn into spirals.
- 5. astronomical unit 1=earth to sun.
- 6. found in halo and bulge and contain even smaller traces.
- 8. spherical region where globular clusters are.
- 10. light year