Across
- 2. a dark region on the sun's surface
- 5. fourth state of matter consisting of charged particles
- 9. model of the universe where Earth stood still in the middle
- 11. proposed the heliocentric model of the universe
- 12. a force of attraction between two objects with mass
- 14. eighteenth century nobleman and astronomer
- 15. center of the sun
- 17. the sun's thin outer atmosphere
- 18. polar displays of colour and light
Down
- 1. combining nuclei of lighter elements to form heavier elements
- 2. constant stream of electrically charged particles given off by the corona
- 3. invented calculus
- 4. sun centered model of the solar system
- 6. largest planet in the solar system
- 7. discovered that planet orbits were elliptical
- 8. closest planet to the sun
- 10. negatively charged particle found in an atom
- 13. apparent backward motion
- 16. positively charged particle located in the nucleus