The planet Uranus has two different symbols, one astrological and one astronomical. The one used in Sailor Moon is the astrological symbol. The astronomer Jerome Lalande suggested the symbol in honor of the planet's discoverer, Sir William Herschel. An "H," representing the first initial in Herschel's last name, sits on top of a globe.

The astronomical symbol is a combination of the symbol for the Sun and for the planet Mars, "as Uranus was the personification of heaven in Greek mythology, dominated by the light of the Sun and the power of Mars." It looks like a circle with a dot inside (the Sun), with an arrow pointing outwards (from the Mars symbol).

The planet Neptune has only one symbol, which is used in both astronomy and astrology. It is a trident, or a three-pronged fork, representing the trident that the Roman god Neptune wielded.

NASA's Solar System Exploration Website.