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Names of the Planets

- question from RoyLee Hall

As we previously described in an article about the days of the week, the names of the planets that we still use today are derived from the names given to these celestial bodies by ancient civilizations. However, I should point out that the ancients were only aware of the Sun, Moon, and the five planets closest to Earth. The outer planets were not discovered until relatively recently after the invention of the telescope, and these were named by the astronomers who discovered them.

NASA photos of the planets and the Moon

Uranus was discovered by the British astronomer William Herschel in 1781. Herschel originally planned to name the new planet Georgium Sidus, Latin for "George's Star" in honor of King George III. Luckily, fellow astronomer Johann Bode convinced Herschel to follow the tradition of naming planets in honor of mythological gods. The name Herschel chose was Uranus, the Roman god of the heavens who was the father of Saturn and the grandfather of Jupiter. The equivalent of Uranus in Greek mythology is Ouranos.

The next planetary discovery was perhaps one of the greatest accomplishments in the history of astronomy. After studying the orbit of Uranus during the late 1700s and early 1800s, discrepancies were noted between the location of the planet predicted by Kepler's laws of orbital motion and the actual position of the planet. Several astronomers concluded that there must be another large planet whose gravitational attraction was perturbing Uranus from its proper orbit. Englishman John Adams and Urbain Leverrier of France were both mathematicians who independently solved for the location of this hypothetical planet in 1845 and 1846. Shortly thereafter, German astronomer Johann Galle observed a new planet located almost exactly where it was predicted to be. The planet was given the name Neptune after the Roman god of the sea. Neptune's counterpart in Greek mythology is Poseidon.

Astronomers of the late 1800s also believed that yet another planet must exist beyond Neptune to account for additional discrepancies in the orbit of Uranus. One of the greatest advocates of this belief was American astronomer Percival Lowell. Lowell carefully calculated a position for this planet and searched for it until his death in 1916. Unfortunately, Lowell's position placed the body in the same region of the sky as the Milky Way. This region is densely packed with stars making it difficult to detect the motion of a distant object against the brightly-lit background. It wasn't until 1930 that American astronomer Clyde Tombaugh finally confirmed Lowell's calculations when he discovered an object very close to the predicted position. Ironically, the presumed perturbations in the orbit of Uranus that led to its discovery later proved to be non-existent, but the discovery of this tiny world was still a remarkable achievement. Though it is no longer considered a true planet, the object was named Pluto for the Roman god of the underworld. The Greek god of the underworld had been called Hades.

That brings us back to the inner planets, the motions of which had been observed by ancient peoples since long before the dawn of recorded history. The names of the planets Mercury, Venus, Mars, Jupiter, and Saturn as well as the Sun and the Moon (which the ancients believed were planets as well) are derived from Latin names given to these bodies by the Romans. These names were simply substitutions of Roman gods in place of names given by the earlier Greeks. It is believed that the names given by the Greeks were also inspired by even earlier civilizations going back to the ancient Sumerians. The Sumerians were the earliest civilization in recorded history, dating back to about 3500 BC. Much of the knowledge and many of the practices of the Sumerians were passed down through the Babylonians, the Assyrians, the Hittites, the Phoenicians, the Greeks, and the Romans to modern Western civilization. The naming of the planets after mythological gods is only one of the many Sumerian traditions that we still use today.

While the exact names of some of the early gods for which the planets were named have become a bit sketchy with time, the following table compares how those names are believed to have evolved over the course of history.

Names of the Planets
Mythological Origin	Sumerian	Babylonian	Phoenician	Greek	Latin	English
goddess of the earth	Ki or Ninhursag	Aruru	Athirat	Gaea	Terra	Earth
god or goddess of the moon	Nanna	Sin	Yarikh	Selenê	Luna	Moon
god of knowledge or communication	Enki	Ea or Nabû	Taaut	Hermes	Mercurius	Mercury
goddess of love	Inanna	Ishtar	Astarte	Aphroditê	Venus	Venus
god of the sun	Utu	Shamash	Shamash	Helios	Sôl	Sun
god of death or war	Gugalanna	Nergal	Resheph	Ares	Mars	Mars
supreme god, god of the sky and storms	Enlil	Marduk	Hadad or Ba'al	Zeus	Iuppiter	Jupiter
god of harvests or agriculture	Ninurta	Ninurta	El	Kronos	Saturnus	Saturn

When compared in this form, the progression from ancient beliefs to the modern day becomes quite clear. Indeed, it is extraordinary to realize that the names of the planets we still use in our modern age can be directly traced back to the religious practices of the earliest civilizations over 5,000 years ago. Furthermore, there is evidence that the design of the Jewish religious symbol called the menorah, with its seven branches, was inspired by these seven celestial objects.
- answer by Molly Swanson, 11 April 2004

What are the colors of the planets?

I heard that some people think Pluto shouldn't be called a planet. Someone also found a new object even bigger than Pluto that may or may not be a planet. It's all so confusing! Can you please explain?

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