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