Across
- 2. The first artificial satellite to orbit Earth
- 4. A natural satellite of a planet
- 5. A large explosion of a star
- 7. The smallest planet in our solar system
- 8. A large cloud of gas and dust in space
Down
- 1. The largest moon of Saturn
- 3. The measure of the amount of matter in an object
- 4. The fourth planet from the sun, known as the red planet
- 6. A scientist who studies celestial objects