The Hubble Space Telescope has peered at Uranus, left, and Neptune to study the so-called "ice giant" planets, but little is known about their interior composition. - NASA / ESA / M. Showalter / L.

Neptune retrograde will occur from July 2 until Dec. 7. Read on for a deeper meaning behind the cosmic event NASA In astrology, the planet Neptune is said to oversee our dreams, creativity, illusions, ...

Imagine predicting an entire planet's existence with nothing but math, and then finding it right where the numbers said it would be. The story of Neptune's discovery is unlike any other in astronomy.