Across
- 5. a region of spacetime where gravity is so strong that nothing
- 6. chemical element with the symbol H
- 8. a plasma of hydrogen and helium
- 10. the Sun and the objects that orbit it
- 11. an atmospheric phenomenon
- 14. a vehicle or machine designed to fly in outer space
- 15. a small planetary-mass object
- 18. a person who is trained to travel in a spacecraft.
- 20. also known as a minor planet
Down
- 1. the distance that light travels
- 2. a gravitational bound system
- 3. Earth's only natural satellite
- 4. chemical element with a symbol he and atomic number of 2
- 7. the galaxy that includes our Solar System
- 9. an astronomical object
- 10. 4.5 billion-year-old star
- 12. a path planets take around the sun
- 13. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
- 16. stars that have burned up all of the hydrogen they once used as nuclear fuel
- 17. a dying star in the final stages of stellar evolution
- 19. controls and regulates the activities of the cell