Across
- 2. Distance light travels in one year
- 4. Average distance from Earth to the Sun
- 6. step-by-step way to test scientific ideas
- 9. The circular path a planet takes around the sun
- 10. an exert of energy
- 11. atoms joining to make energy in a star
- 13. neutral particle in an atom's nucleus
- 15. How bright a star looks from Earth
Down
- 1. negative particle outside an atom's nucleus
- 3. Real brightness of a star from a set distance
- 5. Total energy a star gives off each second(brightness)
- 7. All space we can see from Earth
- 8. positive particle in an atom's nucleus
- 12. Distance unit equal to about 3.26 light-years
- 14. invisible force pulling us down
- 15. building block of matter