Across
- 1. The planet closest to the Sun
- 4. The Milky Way is an example of this
- 6. The particle inside the nucleus which has no charge
- 9. The particle which orbits the nucleus of an atom
- 11. The name of the force which repels two protons
- 12. The biggest planet in the solar system
- 13. The birthplace of stars
Down
- 2. A star the size of the Sun becomes this once hydrogen starts running out
- 3. The lightest element
- 5. The process which occurs in main sequence stars
- 7. An object which orbits another object in the solar system
- 8. The units of weight
- 10. An object so massive not even light can escape