Across
- 1. astronomers theorize that at this single moment the universe was formed
- 4. there are three basic kinds of star clusters: open clusters, ________, and globular clusters
- 6. this cannot be directly seen
- 7. formed when a contracting cloud of gas and dust becomes so dense and hot that nuclear fusion begins
- 8. this shows that the universe is expanding
- 10. an explosion so violent that the dying star becomes more brilliant than an entire galaxy
- 11. enormously bright centers of distant, young galaxies
Down
- 1. it has gravity so strong that anything falling into it is trapped
- 2. a large cloud of gas and dust spread out over a large volume of space
- 3. this galaxy has a bar through the center with the arms extending outward from the bar on either side
- 5. an area of gas that is cooler than the surrounding gases
- 9. the sun stays stable because the inward pull of ______ balances the outward push of thermal pressure from nuclear fusion