Astronomers have traditionally used this symbol for the planet Mercury. It is also the medieval alchemy sign for the element Mercury. The planet Mercury symbol contains the sign for female, but then it’s also topped with “horns” or a crescent. These are to symbolize the winged hat that the Greek god Hermes wore in legend. Hermes was the messenger god of the Greeks.
Mercury’s symbol looks like similar to the symbol for Earth, or femininity. It’s a circle with a cross underneath it. But it also has curved horns coming from the top of the circle. This is the medieval alchemical symbol for Mercury, and has been used for thousands of years. It’s also the symbol that represents the Greek god Hermes, who was the messenger of the gods. In drawings and paintings, Hermes is represented with having wings coming out of his helmet, so this has probably influenced Mercury’s symbol. The Roman god Mercury is the same as the Greek Hermes.
Astronomers have symbols for each of the planets in the Solar System. It’s an easy way to to represent the planets in diagrams and formulae, without having to fully write out the name of the planet. For example, if an astronomer wanted to talk about a planet with 20 times the mass of the Mercury, they might represent it like this: 20 ☿
You can create the HTML entity for this by putting
☿ into your code.
In chemistry, the element Mercury’s symbol is (Hg), and this comes from the Latinised Greek phrase: Hydrargyrum,
from “hydr-” meaning watery or runny and “argyros” meaning silver.
We’ve also recorded an entire episode of Astronomy Cast all about Mercury. Listen here, Episode 49: Mercury.