Astronomers have developed symbols to stand for various celestial objects, including the planets. The symbols all have some kind of meaning, usually linked to the planet’s name or mythology behind the name.
Mercury was named after the winged messenger of the gods, and the symbol is connected to him. The symbol is a circle on top of a cross with two curved horns sticking out of it, representing Mercury’s winged helmet on top of his caduceus – a special staff carried by heralds often depicted with intertwined snakes and wings at the top. Interestingly, the caduceus symbol often represents medicine in North America because it is confused with a similar symbol.
The symbol for Venus stands for Venus’ hand mirror. Interestingly, this is also a common symbol for female. That is not very surprising though considering Venus is the Roman goddess of beauty. This is also the chemical symbol for copper, and mirrors used to be made out of polished copper leading historians to draw a connection between the two.
Earth is not named after a mythological god, so its symbol is not linked to mythology. There are several theories as to what Earth’s symbol means. It is a circle with a cross in the center that could represent the main compass points, which is the most popular theory. Additionally, it could stand for a globe divided into four quadrants. It may also represent the Globus Cruciger, which is a symbol for Christ’s reign over the Earth. This ancient symbol of a circle cut into four has been used in many cultures and even showed up in Norse mythology.
Mars is named after the Roman god of war. The symbol represents Mars’ shield and spear. This is also the male symbol, which makes sense because war was considered a man’s task and occupation.
After the first four planets, the symbols get more complex. Jupiter’s symbol , which looks like an oddly shaped four, has a number of possible meanings. It may be a hieroglyph of an eagle, which was Jupiter’s bird or a lightning bolt – Jupiter’s weapon. It could also be the first letter in Zeus’ name – Zeus is the Greek version of Jupiter – with a vertical line cutting through it to indicate it is an abbreviation.
Although Saturn’s symbol looks somewhat like a decorative “h”, it is actually supposed to represent Saturn’s sickle or scythe. Saturn is the Roman god of agriculture, so the symbol is linked to him.
Uranus is a combination of the symbols for the Sun and Mars. Uranus has the circle with the dot in the center, which is the symbol for the Sun. It also has an arrow branching out from it, representing Mars’ spear. It combines these two motifs because Uranus personified heaven in Roman mythology, and the heavens were ruled by the Sun’s light and Mars’ power.
Neptune is named after the Roman god of the sea, which is very fitting considering the planet’s blue-green color. Neptune’s symbol is the sea god’s trident. There are also symbols for the Sun, Moon, and a number of other celestial bodies, such as asteroids and dwarf planets.
Astronomy Cast has an episode on each planet, so listen to all of them in order starting with Mercury.