Planetary Symbols
Published on Sep 28, 2007 at 11:43 pm.
4 Comments.
Filed under planets, sky lore.
When I am writing equations in my astronomy class, the students often find that I am using some odd symbols now and then rather than spelling out the names of the planets of the Solar System. Well, that is because in some cases it is easier to just put the symbol in the equation rather than spelling out the whole name. Also, the fewer extra letters there are in the equation, the fewer chances there are to make a mistake. But, the symbols that I use for the planets are not just random things that I have made up. Astronomers often use these symbols for just this purpose (where do you think that I picked up the habit?). These same symbols are also used sometimes in planetarium programs to denote the positions of planets in sky views. So, I thought that I’d do a posting on the symbols for the planets.
Though there is some variation among the symbols, most astronomers use a commonly agreed upon set of symbols, with some variations. I don’t think that there is really any official pronouncement as to what symbol represents what planet. Rather, it is just something that we all agree upon by common practice. Many of these symbols come to astronomy from the unscientific practice of astrology. Several centuries ago, astronomers often worked as astrologers, casting horoscopes, in order to make a living. It was hard to find someone to hire you to just do science, so they had to do something to make ends meet. Since astronomers looked at the sky, that gave astronomers some credibility with the public for their doing astrology. It was no doubt this cross interaction that led to the migration of these symbols into the science of astronomy.
Like many others, I readily use these symbols, but I am not sure that I like the idea of astronomers using the symbols of astrology in our field. Already there is a lot of confusion among the public about the distinction between astrology and astronomy. People often ask me about some astrological event, and I’ve even heard a college administrator mistakenly call our program here “astrology” instead of “astronomy.” I have been interviewed several times by local TV stations. One time the caption under my face on the evening news read: Astroprof, Astrology Professor, XYZ College. A similar thing happened with a newspaper. I let them know that they messed up. I have even had students refer to the course as “Astrology”!!!! So, I am thinking that we as astronomers should distance ourselves from astrologers. (Normally I won’t even use the word astrology in this blog because I am afraid that it will trigger a whole mess of astrology ads in the Google ads that run on this site.) Nonetheless, the symbols are commonly used, so I thought that I’d write about them.
Though not a planet, I’ll start with the symbol for the Sun. It is simply a circle with a dot in the middle. This is presumably symbolic of the Sun being the center of the Solar System, with the planets, asteroids, comets, etc. orbiting around it.
Next, we have the symbol for the planet Earth. That is a circle with a cross in it. X marks the spot, so to speak. This is where we are located and from where we observe the universe. I am told that the vertical and horizontal line really represent a line of longitude and the equator.
The next symbol that I’ll mention is that for the planet Venus. I’ve heard two explanations for this symbol. One is that this represents the goddess Venus’ hand mirror. Another explanation that I’ve heard is that the circle signifies the Sun, and the horizontal bar on the line below the circle signifies that Venus always moves back and forth to either side of the Sun in the sky. Whatever the origin of the symbol, most of you will recognize that this is also the symbol generally used to signify “female.”
Very similar to the symbol for Venus is the symbol for Mercury. Like the Venus symbol, I’ve heard two different tales for Mercury’s symbol. One explanation is that this symbol represents the god Mercury’s caduceus (his staff). The “wings” on top of the symbol represent Mercury’s winged helmet. The other explanation is similar to the alternate explanation of Venus’ symbol. According to this second interpretation of the symbol, Mercury’s symbol shows the Sun with the bar below it signifying that the planet goes back and forth to either side of the Sun just like Venus. In this second interpretation, the wings on the top of the symbol signify that Mercury does what Venus does, but only much faster.
We’ve already discussed Earth’s symbol, so I’ll move on to talk about Mars. The symbol for Mars represents the god of war’s shield and spear. It is often speculated that the Greeks and Romans tied the planet Mars to their god of war because of the planet’s reddish orange color. As with Venus, though, the symbol for Mars is also used completely outside of the field to represent something other than the planet itself. This symbol is the typical symbol for “male.”
The symbol for the planet Jupiter looks a lot like a stylized 4. In fact, it is sometimes said that it is a 4 to show that Jupiter is the fourth planet from the Sun. However, that sounds rather made up, and I am not sure if there is anything to that. What I’ve heard for this symbol is that it represents Jupiter’s arm holding a thunderbolt. Jupiter (or Zeus, the Greek equivalent) was often portrayed in antiquity as holding a bolt of lightning. My rendition of this symbol is rather plain. I have seem some very stylized versions, with a much more curved form that looked a lot more like a fancy figure 4 than this one.
The symbol for the planet Saturn looks like a fancy h. Some versions look far fancier than mine, and some don’t have the little curve on top of the h like mine, but have a cross piece instead. I’ve heard two different interpretations of this symbol, too. Some say that this represents the god Saturn’s scythe. However, I have more often heard that this is Saturn’s thrown upon which he sat. In mythology, Saturn was the father of Jupiter as well as the god of agriculture and the harvest.
There are two commonly used symbols for the planet Uranus. The first of these resembles a cross between the symbols of the Sun and of Mars. It is sometimes referred to as a very stylized shield and spear. Uranus is a Latinized form of the Ouranus, which was the Greek god of the sky and father of Saturn and many of the other gods. Interestingly, this symbol was also sometimes used by alchemists to represent the element platinum. This is the symbol that I have most often seen for the planet Uranus. 
However, there is another one that is sometimes seen. This second symbol has the form of a stylized H, reportedly honoring William Herschell, who discovered the planet Uranus. At the time of his discovery, he originally wanted to name the planet “George,” but that name wasn’t accepted by the astronomical community as a whole. Johann Bode suggested that Herschell name the planet “Neptune” because of its bluish-green color. However, Herschell didn’t go along with that. If he couldn’t name the planet George, he wasn’t going to name it Neptune. So, he eventually settled on the name Uranus. That makes sense, since in mythology Uranus was the father of Saturn who was the father of Jupiter. That put successively the outer planets as representing older and slower gods the farther they were from the Sun (and the slower that they moved).
The planet Neptune got its name from the fact that it appears a greenish-blue. 
So, the name Neptune that was rejected by Hershell for his planet was adopted for the next planet outward from the Sun. The symbol for the planet represents the sea god Neptune’s trident. The symbol that I have to the left is a common one for the planet, but occasionally I see this other more streamlined symbol. Either way, they both represent Neptune’s trident (as opposed to the two symbols for Uranus that are quite different).
Those eight planetary symbols, plus the symbol for the Sun, wrap up the symbols for the planets. 
But, for the sake of completeness, I should mention one more symbol, and that is the one for Pluto. For most of the Twentieth Century, Pluto was considered a planet, and so it had a symbol. The symbol for Pluto was a combination of the letters P and L. These were the first two letters of the name Pluto, and they were also the initials of Percival Lowell, the astronomer who began the search for a planet beyond Neptune (though it was actually Clyde Tombaugh who discovered it).
-Astroprof
burçlar on May 3, 2008 at 4:17 am: 1
thanks for info
Tom C on May 13, 2008 at 10:03 am: 2
Thanks, I used your planet symbols for a ActiveVote quiz for my 8th graders
hannah montanna on August 11, 2008 at 4:12 am: 3
saturn and uranus’s symbols are not correct
Astroprof on August 11, 2008 at 8:39 am: 4
Those are the two most commonly seen symbols for Saturn and Uranus around the astronomical community.