Across
- 2. The lightest element and main fuel of stars.
- 3. A baby star still forming inside a cloud of gas.
- 9. The distance around a circle.
- 10. A huge ball of hot gases that gives off light and heat.
- 11. A machine used to speed up particles.
- 12. The theory that explains how the universe began.
- 14. The first synthetic element discovered.
Down
- 1. How bright a star looks from Earth.
- 4. Positively charged particles in an atom’s nucleus.
- 5. Very tiny particles that make up protons and neutrons.
- 6. A cloud of gas and dust where stars are born.
- 7. Particles in an atom with no electric charge.
- 8. The actual brightness a star gives off.
- 11. What something is made of.
- 13. The element formed when hydrogen fuses in stars.
- 15. Same element but has different numbers of neutrons.