This is the 9th in a series of caches based on the Solar System. Solar System #8 Neptune is the 8th planet from the Sun (Solar System #1), 5.2km from the 1st cache, 4,503,000,000 km in reality. The remaining 7 (Venus, Mercury, Earth, Mars, Jupiter, Saturn & Uranus) are placed at increasing intervals from 'The Sun' on theoretical orbits i.e not linear but at increasing distances in differing directions.