“The planets - their location in the sphere, and their interaction with each other - are the symbolic heart of astrology; all other considerations - houses, signs, fixed star alignments - are secondary considerations that take their place as supporters and moderators of planetary meanings."
--Deborah Houlding
The planets are one of, if not THE most important part of astrology, but lots of people don’t spend much time talking about them! Most people focus on the signs because their archetypes seem easier to apply to people than the planets sometimes. Even though most focus on the signs in astrology, knowing what the planets represent is vital to be able to understand your birth chart. Without the planets, there’s not much of a chart to interpret. A solid understanding of the planets results in a better understanding of astrology overall.
The planets in astrology represent certain principles, types of experiences, and needs, drives, or desires we have that need to be expressed or fulfilled in some way. They are what acts out your chart. To put it simply, and how most introductions to planets do, planets are WHAT you do, while signs are HOW you do it. There are lots of different approaches to understanding the planets in your chart depending on the branch of astrology and the tradition you’re using. Natal astrology, horary, electional, modern western, traditional and vedic all use the planets somewhat differently. Personally, I prefer to mix both modern and traditional approaches.
I’m just going to be touching on the western modern and traditional significations of the planets in natal astrology because that’s what I’m most familiar with. The traditional significations we use today mainly come from Vettius Valens, an astrologer from the hellenistic period, around the 2nd century. Even if you don't use traditional astrology, modern astrology stemmed from hellenistic astrologers' observations and studies, so it's extremely helpful to understand the roots of modern approaches.
The Sun:
In modern astrology, the sun represents your ego, identity, and life force. You’ll usually see it described as your vitality, your active & outward self-expression. It's usually described as the "general outline of your personality".
In traditional astrology, the sun represents the intellect and intelligence, authority, honor, public reputation, judgement and action. It also represents people that are highly honored, and religious figures. It's also one of the planets often associated with father figures.
The Moon:
In modern astrology, the moon represents how you express your feelings or emotions, your moods, reactions to things, and your subconscious. It's also usually described as how you nurture your loved ones and form close, very personal relationships.
In traditional astrology, the moon represents the physical body, your physical appearance, beauty, the mother, possessions, wanderings, and travels. It also represents your habits and routines.The moon is usually associated with motherly figures, caretakers, and most feminine people.
Mercury:
In modern astrology, Mercury represents your thought processes, intellect, logic, and communication in all forms (speaking, reading, writing, etc.)
In traditional astrology, Mercury represents education, reasoning and debate, critical thinking & judgement, strategy, explanations & interpretations. It also represents numbers, youth, games, service, discoveries & technology, hearing, and of course, communication. In terms of people, Mercury represents doctors, advisors, philosophers, prophets, interpreters of any kind (including astrologers), and people who use their charm and wit to gain something.
Venus:
In modern astrology, Venus represents values, social skills, beauty, relationships (romantic AND platonic), and your personal taste. In traditional astrology, Venus represents giving & receiving, desire, love, joy, laughter, beautiful things, gains, reconciliation, marriage, friendships, art, music, and anything pleasing to the senses. In terms of people, Venus also represents feminine people.
Mars:
In modern astrology, Mars represents your drive and motivation, impulses, instincts, how you go after things in life, and intense emotions like anger.
In traditional astrology, Mars represents brute force, violence, theft, sabotage, wars, loss of goods, vanity & inconsiderate, self-serving actions, anger and actions driven by anger, separation & cutting things off (severing).
Jupiter:
In modern astrology, Jupiter represents optimism, freedom, justice, luck, philosophy, beliefs, religion & generosity.
In traditional astrology, Jupiter represents child bearing, desire, love, alliances, knowledge, abundance, gifts, justice, government, freedom, rank, religious figures/authorities, inheritance, profits, charity, and wealth.
Saturn:
In modern astrology, Saturn represents restriction, limitation, self-control, delays, obstacles, and hardships.
In traditional astrology, Saturn represents deceit, malicious intent, pettiness, self-deprecating actions, worries, solitude, undermining, false appearances, misery, secrets, obstacles, punishments, restrictions, and sluggishness.
The planets I just touched on are the 7 traditional/visible planets. Uranus, Neptune, and Pluto weren’t discovered until much later, so they didn’t play any part in early astrology. There’s a lot of disagreement on how much or how little these planets represent, but I’ll talk about the significations you generally will see.
Uranus:
Generally, Uranus represents sudden and/or radical changes, progression in society, revolutions, unconventional ideas, and inventions.
Neptune:
Neptune usually represents illusions, imagination, deception, escapism, and (sometimes) spirituality.
Pluto:
Generally, Pluto represents power, authority, dominion, destruction, upheaval, and obsessions.
The planets don’t all have the same level of personal importance! The faster moving inner planets (Sun, moon, Mercury, Venus, and Mars), are all more significant on a personal level. Jupiter and Saturn are usually called the “social” planets, still more significant than the generational planets, but not as significant as the inner ones. The 3 outer planets (Uranus, Neptune, Pluto) all move so slowly that they can stay in one sign for up to 30 years, so they’re called generational planets. Obviously “generational” implies that there’s less of a personal impact, because it affects very large groups of people.
There’s a lot of disagreement over what the outer planets really represent, how they should be used, and how significant they are or aren't. They’re relatively new to astrology and there are a lot of different ways that different astrologers prefer to use them, but that’s a whole topic of its own.