Across
- 4. ball of gas held together by gravity
- 5. explosion of a star
- 8. from outside the earth
- 10. contains billions on stars
- 11. orbiting a planet
Down
- 1. inescapable gravity
- 2. expanding universe
- 3. the scientific study of celestial bodies
- 6. code word
- 7. collapsing universe
- 9. dwarf planet