How did the planets get their names? What are the names of the planets in classical mythology? What does the morning star and evening star mean?
Except for Earth, all the planets in the Solar System are named after Greco-Roman deities. Planets such as Mercury, Venus, Mars, Jupiter and Saturn, which have been known since ancient times, were identified with a deity according to their physical properties and were named after the deity with which they were identified. This tradition has been continued for the planets discovered later, such as Uranus and Neptune.
Mercury: The Smallest Planet
Mercury, the closest planet to the Sun, is also the smallest known planet in the Solar System. A Mercury day lasts about 1407 hours, and a Mercury year lasts about 88 days. The surface temperature varies between -170°C and +420°C.
Mercury, like Venus, can only appear in the sky just before sunrise and just after sunset. This situation caused Mercury to be considered as two separate celestial bodies in Ancient Greece. The morning star is named Apollo and the evening star is called Hermes.1
Apollo is one of the 12 Olympian gods in Greek mythology. He is the god of art, healing and light. He is usually depicted as a young man playing the lyre.
On the other hand, Hermes is considered the herald of the gods and the fastest. No wonder, therefore, that the evening star, which appears for a very short time just after sunset, is named after Hermes. Like Apollo, he is one of the 12 Olympian gods.
Mercury, which gives the planet its current name, is the Roman equivalent of Hermes. In many ways, it shares common features with Hermes. The ancient Romans held a Mercuralia celebration in honor of the god Mercury every 15 May.
In astrology and occultism, Wednesday is Mercury day.
Venus: Earth’s Extremely Hot Twin Sister
Venus, the second closest planet to the Sun, is hotter than Mercury due to its dense atmosphere filled with carbon dioxide. The surface temperature varies between 430°C and 500°C. Its rotation around its axis is reversed compared to other planets in the Solar System, that is, on Venus the Sun rises in the west. Another interesting fact is that a day on Venus lasts 243 days and a year lasts 225 days. So if you’re on Venus, you can celebrate New Year’s Eve twice in one day.
Venus, like Mercury, only appears just before sunrise and just after sunrise. However, it is easier to observe than Mercury because it is very bright. People have used the terms “evening star” and “morning star” for Venus as well as for Mercury.
The ancient Greeks named Venus in the morning as Phosphorus, and Venus in the evening as Hesperus. These terms were later romanized exactly, and Phosphorus was replaced by Lucifer, and Hesperus by Vesper.
Lucifer means light-bringer.
After it was proven that these two celestial bodies were actually a single planet, the names Lucifer and Vesper were used for a while. Eventually, however, the planet was named after Venus, the Roman goddess of love and beauty, because of its shining brilliance.
Venus, which has many features in common with Aphrodite in Greek mythology, is usually depicted as a nude woman in Hellenistic and Roman art.
In astrology and occultism, Friday is the Venus day.
Mars: The Red Planet
A day on Mars, the closest planet to the Sun after Earth, lasts 24 hours 37 minutes. In this respect, it is quite similar to Earth. But a Martian year is about 687 days. The surface temperature varies between -110°C and +35°C.
Mars is also known as the Red Planet because of the iron oxide on its surface. With this aspect, it has always attracted the attention of people in ancient times.
The ancient Greeks associated Mars with blood because of its color and named the planet after Ares, the god of war.
After the Romans conquered Greece, Mars, one of the Roman gods, was identified with Ares and the Red Planet was named Mars.
According to legends, the god Mars is the father of Romulus and Remus, the founders of Rome.
In astrology and occultism, Tuesday is Mars day.
Jupiter: A Gas Giant
Jupiter, the fifth closest planet to the Sun, is also the largest planet in the Solar System. A Jupiter year lasts approximately 4333 days.
This largest planet in the Solar System is named after Jupiter, the king of the gods and god of the sky in Roman mythology.
The Greek equivalent of the god Jupiter is Zeus. Both are the most important gods of their time. They are often depicted with a lightning bolt in their hands.
In astrology and occultism, Thursday is Jupiter day.
Saturn: The Ringed Planet
A year on Saturn, the sixth closest planet to the Sun, takes 10759 days, or about 29.5 years. It is the second largest planet in the Solar System, but its density is lower than that of water. So if we could drop Saturn onto a sea, it wouldn’t sink.
Since it is visible to the naked eye, people have known about Saturn since ancient times. The ancient Greeks named this planet after the harvest god Kronos. Often depicted with a scythe or sickle in his hand, Kronos was deposed by his own son, Zeus.
The Roman equivalent of Kronos is Saturn. Inspired by the Greeks, the Romans named this planet after Saturn.
The Romans held the Saturnalia Festival every December in honor of the god Saturn.
In astrology and occultism, Saturday is Saturn day.
A year on Uranus, the seventh planet closest to the Sun, lasts 30688 days, or about 84 years. It is one of the coldest planets in the Solar System. The surface temperature drops down to -220°C.
Rarely visible to the naked eye, Uranus has been thought of as a star for ages. At the end of the 18th century, it was proved that it is not a star but a planet.
Uranus, after whom the planet is named, is one of the first gods in Greek mythology and is the personification of the sky. He is both the son and husband of Gaia (Earth).
Uranus, who had many children with Gaia, hated them. Thereupon, Gaia devised a plan against Uranus. One day, when Uranus came to sleep with Gaia, his own son Kronos castrated his father with a sickle. After that day, the reign of Kronos began and Uranus lost its importance.
A year on Neptune, the eighth closest planet to the Sun, takes 60182 days, or about 165 years. The planet, which is similar to Uranus in many ways, was previously thought to be a star, but in the mid-19th century it was discovered to be a planet. The substance that gives the planet its blue color is methane on its surface.2
After a long debate over the name, tradition was preserved and this blue planet was named after Neptune, the god of the seas in Roman mythology.
Neptune is often depicted as a bearded man holding a trident. Its counterpart in Greek mythology is Poseidon.
Pluto – It was demoted from planetary status in 2006 and is now considered a trans-Neptune dwarf planet. Pluto completes one orbit around the Sun in approximately 248 years. It is named after Pluto, the ruler of the underground in Greco-Roman myths. Pluto is often seen as the same as Hades.
Eris – It is one of the trans-Neptune dwarf planets. It takes about 559 years to complete one revolution around the Sun. It is named after Eris, the goddess of discord, strife and instigator in Greek mythology. Its equivalent in Roman mythology is Discordia.
Haumea and Makemake, the other trans-Neptune dwarf planets, took their names from other mythologies.
- “The Planet Observer’s Handbook”, Fred W. PRICE, Cambridge University Press, ISBN: 9780521789813
- “Neptune“, Solar System Exploration, NASA, August 28, 2022