How did the planets get their names?
The orbiting planets have names that date back to the dawn of history. Three of these names, however, were designated in modern times. The other five were given so long ago that we do not know who chose them or why these particular names were selected.
Thousands of years ago, the motions of the heavenly bodies were studied by astronomers in many lands. The Babylonian, Egyptian, Hindu and Chinese stargazers named the planets with words from their own languages. Astronomers of olden times counted seven planets, including the sun and the moon. We no longer classify these two heavenly bodies as planets. The sun is a star, the moon a satellite.
The Romans added little or no information to the study of early astronomy, yet the names they gave to the planets have survived to the present time. Six planets were named for legendary deities of ancient Rome. The remaining two have names taken from gods worshiped by the ancient Greeks.
In July, we expect one of our far flying spacecraft to send back pictures of a planet named for an ancient god of war. The planet is Mars, and it was named for a deity worshiped by the ancient Romans. The planet Venus was named for the Roman goddess of beauty and gardens. She is the only planet named for a lady. Mercury was the message carrier of the Roman gods, and Jupiter was their king. Saturn was named for an ancient god of seeds and farming. According to Roman legend, he had been king of their gods at one time.
These are the only planets named by the ancients, for they were the only planets of which they were aware. Two of the remaining planets are so remote they cannot be seen without a telescope, and the third can barely be spotted even if you know just where to look. They were not discovered until the telescope was invented. Uranus, next to Saturn, was found first, and the newly discovered planet was given a name in keeping with its sister and brothers. Uranus was the Greek god of the heavens. Neptune was discovered next and named for the Roman god of the sea. Pluto was named for the Greek god of a legendary lower world where shadowy ghosts and departed spirits were thought to dwell.
The people who named the visible planets were somewhat confused by the planets wandering paths in the sky. Planet is coined from an older word meaning wanderer. Mistaking the different positions of Venus for two separate planets, the Romans called the morning star Lucifer and the evening star Hesperus.