What is a Planet in Astrology?

Planet is a term used by astrologers (and astronomers), which includes the known planets of our Solar System (listed in order from the Sun outwards):
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

In Astrology, a Planet may also (for the sake of convenience, not accuracy) refer to the two heavenly bodies which are also called Lights or Luminaries (because they send or reflect light to us on Earth): the Sun (a Star) and the Moon (a Satellite of planet Earth). Since we are Earthlings and observe the heavens from Earth itself, Earth is not often mentioned as a "Planet" in astrology because we don't see it in the heavens.

Wandering Stars

The origin of the word Planet is a Greek term which translates as wandering star. Even though the nearby planets and the distant stars both appear to be pinpoints of light in the night sky, the Planets (including the Moon) appear to "move" or to be "wandering" across the heavens through the twelve zodiac signs over the course of days or years, while the stars appear to remain fixed in position (relative to each other). Most of the verses in the Bible which mention "stars" are really referring to these "wandering stars" we now know as planets.

Stars appear to twinkle, but planets have a steady light. The Sun is also a star, but we are so close to it that its light overpowers the light of the distant stars, and we cannot see them when the Sun appears above the horizon.

From our point of observation, the Sun and Moon and all the planets appear to move within a narrow 7 and 1/2 degree band in the sky called the Zodiac - which comes from a Greek expression meaning "circle of animals". (Eight of twelve Signs have animals as their symbol).

The Ten Planets in Astrology

Planet as defined in Astrology includes all of the seven heavenly bodies which ancient astrologers could see in the sky, plus the three planets discovered since the invention of telescopes. The Planets, listed in order of distance from the Sun (with their Roman/Greek mythical links) are:

1. Mercury - named after Mercurius or Hermes (Messenger of the gods)
2. Venus - named after Venus or Aphrodite (goddess of Love and Beauty)
3. Mars - named after Mars or Ares (god of War)
4. Jupiter - named after Jupiter (Jove), or Zeus (King of gods)
5. Saturn - named after Saturn or Kronos (god of Time)
6. Uranus - named after Uranus or Ouranos (god of Sky)
7. Neptune - named after Neptune or Poseidon (god of Sea)
8. Pluto - named after Pluto or Hades (god of Underworld)

Though the Sun (a Star) and the Moon (a satellite of Planet Earth) are not planets by the usual definition, for the sake of convenience astrologers refer to them as "Planets" too:

1. Sun - named after Sol or Helios (also associated with Apollo)
2. Moon - named after Luna or Hecate (also associated with Diana)

In Geocentric (Earth-centered) Astrology, the Earth itself is usually not included in the Planet list because we are living on it and are a part of it. We don't see it in the sky. In Heliocentric (Sun-centered) Astrology, the Earth is considered a Planet because the Sun is the point of observation.

As you can see from the lists above, there are eight planetary bodies and two Luminaries used in Astrology (not counting the 9th planet, Earth). Including them all under the term "Planets" means there are ten Planets found in a horoscope chart, spread among the twelve astrological Signs and twelve Houses of the horoscope.

The Meaning of the Planets in Astrology

Astrology is a symbolic language, and each Planet is a symbol which represents one or more functions of our own psyche. When an astrologer looks at where the Planets are located in a person's birth horoscope, he can find many insights into the workings of that person's inner Self. You could say a Planet represents:

1. a PSYCHOLOGICAL FUNCTION [or a Spiritual Ideal]
   
2. a CAPACITY to EXPRESS a certain PART OF THE PSYCHE
   
3. a POTENTIAL ENERGY which SEEKS EXPRESSION
   
4. a DRIVE or MOTIVATION TO BE or BECOME or DO
   
5. a DESIRE to ACT OUT a CERTAIN THEME
   
6. a NEED or HUNGER which SEEKS SATISFACTION
   
7. an OBJECTIVE which USES THE STRATEGY OF A SIGN
   
8. an ENERGY which has POSITIVE & NEGATIVE POLARITIES
   
9. a CURRICULUM of LESSONS to be learned.

The kinds of strategies for accomplishing these functions are indicated by the Sign the Planet occupies in the horoscope chart, and the the areas of life where this most likely plays out is indicated by the House the Planet occupies.