Across
- 5. How bright a star looks from Earth.
- 8. A natural force that pulls objects toward each other.
- 9. The curved path of a celestial body around another body in space.
- 11. A push or a pull on an object.
- 12. A tiny, neutral particle with no charge in an atom's center.
- 15. A tiny, negative particle that spins around an atom's center.
- 16. The distance from Earth to the Sun, about 93 million miles.
Down
- 1. How bright a star actually is from a standard distance.
- 2. The visible part of the universe we can see from Earth.
- 3. The total amount of energy a star gives off per second.
- 4. A step-by-step way to test ideas and learn about the natural world.
- 6. A unit of distance used in astronomy, equal to about 3.26 light years.
- 7. Fusion The process where atomic nuclei combine to release huge amounts of energy.
- 10. A tiny, positive particle inside an atom's center.
- 13. The distance light travels in one Earth year.
- 14. The basic building block of all matter in the universe.