The planets

The classical seven

The word planet comes from the Greek for wanderer. To ancient observers, seven lights wandered against the fixed stars: the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn. Astrology still calls the Sun and Moon planets for convenience, though astronomers do not.

In this tradition, each planet stands for a part of life. The Sun is identity, vitality and purpose. The Moon is feeling, habit and what comforts us. Mercury is thinking, speaking and learning. Venus is love, beauty and what we value. Mars is drive, desire and conflict. Jupiter is growth, generosity and belief. Saturn is limits, time, responsibility and what we build slowly.

The modern outer planets

Three more planets were found with telescopes: Uranus in 1781, Neptune in 1846 and Pluto in 1930. Astrologers gave them meanings drawn partly from their mythological names and partly from the history of the times when they were found.

Uranus is read as sudden change, independence and invention. Neptune is linked with dreams, imagination, spirituality and confusion. Pluto stands for power, endings and deep transformation. Because they move so slowly, astrologers often treat them as generational: many people born within a few years of each other share the same outer planet signs.

Fast and slow

Seen from Earth, the planets move through the zodiac at very different speeds. The Moon is fastest by far, circling the whole zodiac in about 27 days and changing sign every two and a half days. The Sun takes a year, spending about a month in each sign. Mars takes around two years for a full circuit. Jupiter takes about 12 years, roughly a year per sign, and Saturn about 29 and a half. Uranus takes about 84 years, Neptune about 165 and Pluto about 248.

Mercury and Venus are a special case. Their orbits lie inside Earth's, so from here they never stray far from the Sun: Mercury stays within about 28 degrees of it, and Venus within about 47. That means that over a whole year they cover the zodiac at the same average rate as the Sun. But they swing ahead of it and fall behind it, and at their quickest Mercury can travel about two degrees a day and Venus about one and a quarter, faster than the Sun's one degree. So the traditional order from fastest to slowest is Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

Sometimes a planet seems to stop and move backwards for a while. This is called retrograde motion. Nothing actually reverses: it is an effect of Earth overtaking a slower outer planet, or of an inner planet passing between us and the Sun, rather like a slower car appearing to slide backwards as you pass it on a motorway.

Rulerships and dignity

Each planet rules one or two signs, as you saw in the last lesson. Astrologers say a planet in a sign it rules is in its domicile, or at home, and expresses its nature most easily there. In the sign opposite, it is in detriment, working in less familiar territory. Saturn in Aquarius, for example, is at home. Saturn in Leo, the sign opposite, is in detriment.

These ideas, known as essential dignities, are central to traditional astrology. They are a way of describing how comfortable a planet's symbolism is in a sign, not a judgement of good or bad people.

Key terms

Planet

From the Greek for wanderer. In astrology, the Sun, Moon and the planets of the solar system used in a chart.

Outer planets

Uranus, Neptune and Pluto, discovered with telescopes and slow enough to be shared across a generation.

Retrograde

A period when a planet appears to move backwards through the zodiac as seen from Earth.

Domicile

A sign a planet rules. Astrologers say the planet is at home there.

Detriment

The sign opposite a planet's domicile, where its expression is said to be less at ease.

Try it: Order the planets by speed

Arrange the ten planets from fastest to slowest average motion through the zodiac, as seen from Earth.

Check your understanding