The planets in astrology: what each one represents

The traditional seven

These are the seven classical planets, and the word planet is used loosely here. It comes from the Greek for wanderer, and originally meant anything that moved against the fixed stars, which included the Sun and Moon. The rulerships in the third column are the traditional scheme, expanded on in every sign's ruling planet.

The three modern planets

Uranus was discovered in 1781, Neptune in 1846 and Pluto in 1930, and astrology absorbed each of them within a few decades. They were assigned rulership of Aquarius, Pisces and Scorpio respectively, displacing Saturn, Jupiter and Mars: a change traditional astrologers largely reject.

Uranus counts, for traditional astrologers, as disruption, sudden change, independence and everything that breaks a pattern. Neptune as dissolution, imagination, compassion, illusion and the loss of boundaries. Pluto as power, compulsion, destruction and transformation.

There is an argument to notice here, and it cuts both ways. The meanings assigned were shaped by what was happening when each was found: Uranus by the age of revolutions, Neptune by Romanticism and the discovery of anaesthesia, Pluto by the atomic era and the rise of mass ideology. Defenders read that as the sky and the age corresponding. Critics read it as astrologers naming planets after their own historical moment, and note that Pluto's 2006 reclassification as a dwarf planet changed nothing in astrological practice, which suggests the category was never doing the work.

I'd rank a planet's condition above its sign. A weak Venus in Libra does less than a strong Venus in Aries, whatever the books say.

Personal, social and outer

This division does more interpretive work than any list of meanings, and it follows directly from orbital speed.

Personal planets (Sun, Moon, Mercury, Venus, Mars) move fast enough to differ between people born days or weeks apart. These describe an individual, and they're where a chart reading should spend most of its time.

Social planets (Jupiter and Saturn) take twelve and thirty years respectively, so they're shared with a broad age cohort but still shift within a childhood. They describe how a person meets the structures around them.

Outer planets (Uranus, Neptune, Pluto) spend seven to twenty years in a sign. Everyone born within several years of you shares the placement, so they're called generational.

What makes a planet strong

Astrologers have a well-developed and often-skipped machinery for deciding how much weight a placement carries, and it's more interesting than the sign meanings.

Dignity: a planet in the sign it rules is at full strength; in the opposite sign, called detriment, it is weakened; exalted in a particular sign it is amplified, and in the sign opposite that, its fall, it struggles. Mars in Aries is strong; Mars in Libra is in detriment.

Angularity: a planet in the 1st, 4th, 7th or 10th house is more prominent in a life than the same planet in a cadent house. This is set out in angular, succedent and cadent.

Condition: whether it is retrograde, combust from being too near the Sun, or tightly aspected by benefics or malefics.

Modern popular astrology dropped most of this, which is part of why sign-based readings feel flat: without dignity, every placement has the same weight, and a chart becomes a list instead of a hierarchy.

Why the week is in that order

The seven classical planets gave the days of the week their names, and the order of the days is a piece of astrology hiding in plain sight. Arrange the planets by apparent speed, slowest first: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. This is the Chaldean order, and late antiquity assigned the hours of the day to the planets in that sequence, cycling round. Twenty-four hours later the cycle has advanced by three places, so the planet ruling the first hour of the next day is three steps on: Saturn's day is followed by the Sun's, then the Moon's, then Mars's, Mercury's, Jupiter's and Venus's.

Saturday, Sunday, Monday. Then, in the Romance languages, mardi, mercredi, jeudi, vendredi for Mars, Mercury, Jupiter and Venus, which English replaced with the Germanic gods Tiw, Woden, Thor and Frigg standing in for the same planets. Every calendar on your phone runs on a planetary-hour system from the second century, and almost nobody who uses it knows.

Benefics, malefics and sect

Traditional astrology sorted the planets by temperament before it sorted them by meaning. Jupiter and Venus are the benefics, held to bring ease; Mars and Saturn the malefics, held to bring difficulty; the Sun and Moon the lights, and Mercury neutral, taking its character from what it touches. Modern astrology softened this into 'challenging' and 'flowing', but the older scheme is what the aspect readings and the dignity tables assume.

The refinement is sect. In a day chart the Sun, Jupiter and Saturn are 'of the sect' and behave better; in a night chart the Moon, Venus and Mars do. So Saturn in a day chart is a stern but constructive planet and in a night chart the harsher one, while Mars is worse by day and more usable by night. This one idea explains a great deal of what a traditional reading says about the same planet in two charts, and it is covered in sect: day and night charts.

How long each spends in a sign

The right-hand column is the practical guide to how much a placement can say about you. A Moon sign separates you from most people born that month. A Neptune sign does not separate you from anyone you went to school with.

The bodies astrologers argue about

Beyond the ten, practitioners disagree about what else belongs. Chiron, a small body between Saturn and Uranus found in 1977, has been widely adopted as 'the wounded healer'. The four largest asteroids have their followers, discussed in asteroids in astrology. The lunar nodes, which are points and not bodies, are used by almost everyone. Lilith, in its most common form, is a point too, the empty focus of the Moon's orbit.

AsterNym computes the ten planets and the nodes, and states the reason for stopping there on the minor bodies page: a smaller set computed properly is preferable to a larger one computed through a route it has not verified. Where a planet is missing from a chart on this site, that is why.

Reading a planet in three parts

Every placement is a sentence with three components, and the order stops the interpretations blurring.

The planet is what is acting. The sign is how it acts. The house is where in life it acts. Saturn in Gemini in the third house reads as limitation and structure, expressed through communication and thinking, in the arena of speech, learning and siblings. Change only the planet and something entirely different is happening in that same arena.

Then read the aspects to see which planets are arguing with which. That's the point where a chart stops being ten separate statements and becomes something with internal structure, and it is also the point where over-interpretation gets easy, so the discipline of starting with the tightest aspects counts.