Across
- 4. Variant of an element with different numbers of neutrons.
- 5. How bright an object like a star appears from Earth.
- 8. Particle with a negative charge in an atom.
- 10. Measure of how hot or cold something is.
- 11. The element formed from hydrogen in stars, symbol He.
- 12. Fundamental particle that makes up protons and neutrons.
- 13. Fundamental substances that make up matter.
- 14. The particle with a positive charge in an atom.
- 15. Particle with no charge in the nucleus.
Down
- 1. The primary fuel of stars, symbol H.
- 2. A very young star in the early formation stage.
- 3. The initial cosmic explosion that created the universe.
- 6. A cloud of gas and dust in space, often where stars are born.
- 7. The total distance around a circle or sphere.
- 9. The center of an atom containing protons and neutrons.