Everyone knows the names of the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune (sorry Pluto). We also know the helpful saying to remember this: “My Very Excellent Mother Just Served Us Nachos.”

Fewer people know the better one drawn from the following passage in the gospel of Matthew :

Now the birth of Jesus Christ took place in this way. When his mother Mary had been betrothed to Joseph, before they came together she was found to be with child from the Holy Spirit. And her husband Joseph, being a just man and unwilling to put her to shame, resolved to divorce her quietly. (Matthew 1:18-19)

But this post isn’t about remembering the planet names. This post is about remembering WHY the planets are named what they are named. Everybody knows that the planets correspond to classical characters in mythology. But I’m answering the question “Why did the ancients connect THAT spot of light — and not any other spot of light — to this PARTICULAR deity — and not another deity?”

As I’d like to show, there is actually an answer.

Background Knowledge of Astronomy

If you want to know why the planets are named what they are named, this will require some background astronomy knowledge. You need to know how things are moving. First, every day, the entire sky spins because the Earth spins. The stars look like they are “fixed” in a sphere around the Earth that goes around once a day. That is why the stars were called “fixed stars.”

However, there were particular bodies in the sky that did not stay “fixed.” Instead, they wandered around the sky in roughly the same path that the Sun and Moon took. These were called ἀστέρες πλανῆται (“asteres planetai”) or “wandering stars.” That’s where we get the name “planet.”

But that’s not all. While the background stars spin once a day, that is not their only motion. They also move throughout the year, appearing in slightly a different position each day throughout the year. This motion happens because the Earth is not only spins, it orbits, too. When you take away the distracting spin of the Earth, the following video shows how the Sun, Moon, and all the planets move through the background stars throughout the course of a year.

That is what is being seen in slow motion from the Earth. This view is complicated by the tilt of the Earth, by the disappearance of the stars in the day, and by the fact that it is not at all obvious to the casual observer that the Earth is actually moving.

That is why the ancients, instead of factoring in the “orbits” of the planets, merely looked at their motion against the background stars. They tracked these motions against the “Zodiac,” which are the twelve constellations that the Sun, Moon, and all the planets travel through in the sky. Though some random bodies in the sky like comets and supernova can appear almost anywhere in the sky, the solar system bodies do not. This is because the Solar System is essentially a flat disc, with only a little bit of difference between all the orbits.

The following view, from the program “Universe Sandbox” shows what this looks like away from the Earth:

The bright points of light that did not move like the other stars received names from the ancient star-watchers, not on a RANDOM basis.

Instead, they were named based on their ACTUAL BEHAVIOR AND APPEARANCE in the sky. Below, the characteristics of the planets in the sky are explained:

Mercury

Except for the Moon, the planet Mercury is the fastest body to move against the background stars.

But not only is it “the fastest,” it also has a strange quality of movement. The orbit of Mercury is the most eccentric and inclined of the planets. Being the most eccentric means its ellipse is the most “un-circular” of all the planets. Being the most inclined means its is tilted the most from the disc of the solar system. This makes him quite strange to observe. Additionally, Mercury is also closest to the Sun, and closer to the Sun than the Earth is. That means that he can only be seen at sunrise or sunset, and he will only appear close to the horizon, or not at all.

An astronomer looking at Mercury would notice that over the course of a few days, he will rise in the heavens, and then disappear back at the horizon of the Earth. Look at the path of Mercury over the course of several days at the time of 5:27am:

What better behavior for a planet could there be — quickly rising to the heavens and quickly descending to the Earth again — to be associated with the swift-footed “messenger of the Gods”?

This is also the reason for grouping certain things that are called “mercurial” — they are hard to pin down and define. Notice how C.S. Lewis described the attributes of Mercury in various ways in medieval literature:

Gower says the man born under Mercury will be ‘studious’ and ‘in writinge curious’, . . . The Wife of Bath associates him especially with clerks (D 708). In Martianus Capella’s De Nuptiis, he is the bridegroom of Philologia — who is Learning or even Literature rather than what we call ‘philology’. . . . It is difficult to see the unity in all these characteristics. ‘Skilled eagerness’ or ‘bright alacrity’ is the best I can do. But it is better just to take some real mercury in a saucer and play with it for a few minutes. That is what mercurial means.

That is why if someone is “mercurial,” he will be very hard to pin down, just like it was very hard for ancient astronomers to pin down exactly where Mercury would be against the background stars.

With this understanding and history of the planet’s behavior and mythology, notice how the composer Gustav Holst, in his composition giving themes to each of the planets, made his composition about Mercury just as eccentric as the planet itself:

And that is why Mercury was named “Mercury.”

Venus

Venus is the goddess of love and fertility. Her Greek name is Aphrodite. As for the planet, when Venus is visible, she is the brightest, largest, and most beautiful of all the planets. However, because Venus is closer to the Sun than the Earth, and because Venus is far closer to the Earth than Mercury, the appearance of Venus noticably changes. She is always bright, but she also gets significantly LARGER in the sky, so much so that if you’re looking for it, you can even see her crescent shape.

It is likely not without reason, then, that many of the ancient Babylonian, Akkadian, and Assyrian immages of Innana (Sumerian) and Ishtar (Akkadian and Assyrian) depiction of this goddess of love and fertility show her with HORNS:

And notice Venus’s motion in the sky. She rises, stays aloft in the sky for a while, and then falls into the brightness of the Sun and disappears. Is there a better metaphor of beauty, fertility, and love than that? Take a look at her motion over the course of several months:

The movement of Venus is regular — VERY regular. If you measure Venus against the background stars according to a geocentric earth (like the ancients did), then you will get the famous “pentagram” of Venus that looks like this:

In contrast, look how irregular the position of Mars is against the background stars (the funny symbols on the circle are the signals for the zodiac constellations):

Preserving the associations with love and beauty, Holst explored the themes of Venus with the following song:

Mars

The planet Mars is fifth from the Sun, on an outside orbit from the Earth. His Greek name is Aries. This means that unlike Venus and Mercury, it is possible to see Mars all night long on many nights, because the Sun is on the opposite side of the Earth from the planet, which is impossible for Venus and Mercury with their smaller orbits. Notice how Mars moves across the sky over the course of several months, first in the early morning, and then in the evening:

Because it is red in appearance and difficult to predict its appearance (before modern astronomy), and because of its change from extremely dim to almost the brightest and impressive stars in the sky, it has been associated with the god Mars. Mars is the god of war, and his Greek name is Aries.

He is called “murderous Mars” and “fierce Mars” in the Iliad. He is battle and bloodshed. He marches, rises high and gets bright, shining as a very noticeable red.

Mars lingers in an odd path in the sky, unique among the planets. And as opposed to Venus, the motion of Mars is irregular. As in, VERY irregular. It was the irregularity of Mars’s motion that led Kepler to show that planets move in elipses and not circles. Using the same geo-centric measurement against the background stars that we did above with Venus, look at Kepler’s description of the movement of Mars:

Based on these movements and associations, notice how Holst describes Mars in song, with a very distinctive and noticeable 5/4 time signature:

Jupiter

Jupiter is the fifth and largest planet in the solar system. His Greek name is Zeus. Jupiter is the “ruling” god and ruling planet, and his actions in the sky reflect this role. While Mars may march back and forth, while Venus may gently and beautifully slide across the sky, and while Mercury may zip up and down from heaven to earth, Jupiter is a bright, ordered, and orderly presence in the sky.

It takes Jupiter 12 Earth-years to make one orbit around the Sun. This fact creates a unique quality of the view of Jupiter in the sky. In the video below, notice what the ancient astronomers noticed about the movement of this planet. It stays put for an entire year in a single constellation of the zodiac. Then, after it disappears behind the Sun, it reappears in an new constellation.

Every year, Jupiter appears in the early morning in a different part of the sky, then becomes visible earlier and earlier and earlier in the night until it becomes an evening star that disappears into the Sun again.

This yearly, bright, and regular motion of Jupiter makes him the best representative of the regular and peaceful rule of a good king in power: Jupiter. He regularly visits each of the twelve zodiacal constellations for about one year each.

And despite being the largest planet, Jupiter is also the fastest spinning planet in the entire solar system, making a complete rotation in less than 10 hours. This led Holst to make his musical rendition of Jupiter not only grand and regal, but also quite exciting — and (how else to put it for the planet named after “Jove”) — Jovial.

Saturn

Saturn is the Titan father of Jupiter, who was overthrown by his son. He is the “worst” of all planets in astrology, and he is associated with sickness, old age, time, and death. Have you ever wondered why both Father Time” and the Grim Reaper both carry around a big scythe?

They are all the same person: Saturn, whose Greek name was Kronos or Cronus.

And this association with old age, sickness, time, and death are also reflected in the motion of Saturn. It is the dimmest of all the visible planets (Uranus and Neptune are not visible without a telescope). It also has the SLOWEST movement among the background stars. It takes around two years for Saturn to move from one zodiac constellation to the next.

But there is a strange caveat to all of this. Yes, Saturn is the “worst” planet, but he is not all bad. If you have ever heard of being in the “seventh heaven,” that is Saturn. (Note: the ancients did not believe that “Earth” was a planet, and they included the Sun and Moon in the calculation, so the order of the heavens were: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn.) To be in the “seventh heaven” is to be as far away from the cares and troubles of Earth as it is possible to be. This is also more than an ancient astronomical belief. In mythology, Saturn was the ruler of Earth in the Golden Age of man, according to Hesiod.

In a Christian understanding of this mythology, this would mean that Saturn was the ruler of the Earth at the time of the Garden of Eden. This is why in C.S. Lewis’s science-fiction series Out of the Silent Planet, the angel (“Oyarsa” in the book) set in authority over the planet Mars (called “Malacandra” in the book) says the following to Ransom who is from Earth (called “Thulcandra” by those not from Earth) and about what God (called “Maleldil” in the book) does:

“Then you knew of our journey before we left Thulcandra?”
“No. Thulcandra is the world we do not know. It alone is outside the heaven, and no message comes from it.”
Ransom was silent, but Oyarsa answered his unspoken questions.
“It was not always so. Once we knew the Oyarsa of your world — he was brighter and greater than I — and then we did not call it Thulcandra. it is the longest of all stories and the bitterest. he became bent. That was before any life came on your world. Those were the Bent Years of which we still speak in the heavens, when he was not yet bound to Thulcandra but free like us. It was in his mind to spoil other worlds besides his own. He smote your moon with his left hand and with his right he brought the cold death on my harandra before its time; if by my arm Maleldil had not opened the handramits [that is, in the book, the low river valleys] and let out the hot springs, my world would have been unpeopled. We did not leave him so at large for long. There was a great war, and we drove him back out of the heavens and bound him in the air of his own world as Maledil taught us. There doubtless he lies to this hour, and we know no more of that planet. it is silent.” (C.S. Lewis, Out of the Silent Planet, Chapter 18)

Notice that this is an allusion to the Flood of Noah, as told by Mars, who was worried that the evil of the Earth would spread to a different planet. But anyway, that’s enough of that.

And that is why we have the slowest and dimmest planet named after the worst and most lethal of the ancient gods. Notice how Holst takes this theme in his Planets composition:

Uranus

The seventh Planet Uranus was unknown by the ancients, because it is not bright enough to normally be seen. However, it is technically possible to see it on the darkest nights, with the most careful of eyes, when Uranus is at its brightest, and when you know exactly where to look.

Uranus was discovered by William Herschel in 1781. We see from Wikipedia that it was seen on March 13, 1781 in the constellation Gemini. This is what he saw. At this point and at this date, Uranus was 1,761,000,000 miles away from the Earth, and that is near its closest point that the planet ever reaches Earth. It was also fully illuminated by the Sun, and therefore, Uranus was as bright as it would ever appear. Yet, notice how dim it is:

It takes Uranus 84 Earth-years to travel in its orbit. This means that from the perspective of Earth, it takes nearly a century for the planet to move through the entire zodiac circle. Notice how slowly the planet moves compared to the other bodies in the sky, and how dim it is:

The name “Uranus” comes from the Greek word οὐρανός or “Ouranous.” William Hershel tried to name the planet Georgium Sidus (George’s Star). The following reason was given:

In the fabulous ages of ancient times the appellations of Mercury, Venus, Mars, Jupiter and Saturn were given to the Planets, as being the names of their principal heroes and divinities. In the present more philosophical era it would hardly be allowable to have recourse to the same method and call it Juno, Pallas, Apollo or Minerva, for a name to our new heavenly body. The first consideration of any particular event, or remarkable incident, seems to be its chronology: if in any future age it should be asked, when this last-found Planet was discovered? It would be a very satisfactory answer to say, ‘In the reign of King George the Third’.

Really? King George III? Yes, really.

Luckily for us, cooler heads prevailed in the naming game. An ancient order was preserved in the planet names. Mars is the fourth planet, and his father is Jupiter, the fifth planet. The father of Jupiter, is the sixth planet Saturn. The order obviously points to the idea that the seventh planet should be the father of Saturn, and Hesiod’s Theogony tells us that the father of Saturn is οὐρανός which means “Heaven.” Because we turn those Greek letters into English and call it “Uranus.”

Because of the newness of the planet, there were not any Greek mythological associations to impart to Uranus, so I have no commentary on Holst’s rendition:

However, because “Uranus” means “Heaven,” I do like the reall association with this planet and the very real “Heaven.” It comes after Saturn — sickness, pestilence, old age, and death. Additionally, as I said before:

However, it is technically possible to see it on the darkest nights, with the most careful of eyes, when Uranus is at its brightest, and when you know exactly where to look.

Neptune

The planet Neptune was discovered in 1823 through a cooperative effort.  Johann Gottfried Galle of England was contacted by Urbain Le Verrier of France to explore a spot in the sky, because Urbain Le Verrier thought that an unknown planet could be the reason that the pre-calculated positions of the newly discovered planet Uranus were not being correctly observed in the sky. Sure enough, with Le Verrier’s calculation, Galle saw Neptune.

We read the story of the naming of this planet in this article published by NASA. At first, the planet was going to be named after the man who calculated its position: “Leverrier.” A French Almanac put forward this name and even tried to rename Uranus “Herschel.” The English astronomers put forward the name Oceanus. However, at the suggestion of its discoverer, it was named “Neptune.”

This might seem like a random name. After all, the father of “Uranus” is not “Neptune.” And this is true. It appears the name of Neptune was the result of an argument among 1800s astronomers and not a deliberate affair. However, the Proverb says:

The lot is cast into the lap,
    but its every decision is from the Lord.
(Proverbs 16:33)

And there is likewise something unique to this one, too. Readers of this blog will remember quite well what is above “the Heavens.” That would be “the waters above the firmament.”

And God said, “Let there be an expanse in the midst of the waters, and let it separate the waters from the waters.” And God made the expanse and separated the waters that were under the expanse from the waters that were above the expanse. And it was so. And God called the expanse Heaven. And there was evening and there was morning, the second day. (Genesis 1:6-8)

 Praise the Lord!
Praise the Lord from the heavens;
    praise him in the heights!
Praise him, all his angels;
    praise him, all his hosts!

Praise him, sun and moon,
    praise him, all you shining stars!
Praise him, you highest heavens,
    and you waters above the heavens!
(Psalm 148:1-4)

So funny enough, the naming of the outer-planets follows what we read in scripture about what is “up there,” even if it were by accident.

Short Note on Pluto

The dwarf planet “Pluto” was discovered by Clyde Tombaugh, a 23-year-old Kansan at the Lowell Observatory in Arizona. After a thousands of suggestions for a name, the suggestion of an eleven-year-old schoolgirl in Oxford England named Venetia Burney for “Pluto,” the Roman god of the underworld, was accepted.

While I do not believe this was on her mind, this name for this planet is fitting for a cold and distant planet on the edge of the “outer darkness”

And cast the worthless servant into the outer darkness. In that place there will be weeping and gnashing of teeth.’ (Matthew 25:30) (see also, Matthew 8:12, Matthew 23:13, ).

So, yeah, that does seem to fit quite well, even though it was just happenstance. But also, we should remember that Pluto was recently downgraded from the status of “planet” by the International Astronomical Union in 2006. And look at what we read in the book of Revelation:

Then Death and Hades were thrown into the lake of fire. And if anyone’s name was not found written in the book of life, he was thrown into the lake of fire. (Revelation 20:14-15)

Remember that the Greek version of “Pluto” is Hades, the god of the underworld. So it seems we have a humorous parallel between what happened to the exaltation of “Pluto” in the list of planets and what will happen to the real god of the underworld “Hades” at the last judgment. But that’s just happenstance. I’m sure there’s nothing to that.