Western astrology employs the tropical zodiac which divides the ecliptic into twelve signs of equal length starting at the first point of Aries, which is defined as the point at which the ecliptic (the apparent path of the Sun through the heavens) crosses the celestial equator at the spring equinox. It is important to note that these signs are completely independent of the astronomical constellations after which they were originally named and no longer bear any relationship to them.
Because the calendar is defined by the movement of the Earth around the Sun, and its orbit is very nearly circular, the sign in which the Sun falls on any day of the year is fairly predictable, though it will vary a little due to the effect of the extra day in leap years. These dates are given in the article that deals with each sign individually. To determine the sign in which the moon and other planets fall on any given day, it is necessary to consult an ephemeris or use an astrological computer program which will have a built-in ephemeris
Each sign is ruled one of the planets (note that in astrology, the sun and moon are considered planets, which literally means wanderers, i.e. wanderers among the stars). The traditional rulerships are as follows: Aries (Mars), Taurus (Venus), Gemini (Mercury), Cancer (Moon), Leo (Sun), Virgo (Mercury), Libra (Venus), Scorpio (Pluto), Sagittarius (Jupiter), Capricorn (Saturn), Aquarius (Uranus), Pisces (Neptune).
A planet is strengthened (dignified) if it falls within the sign that it rules. If a planet is in the sign opposite that which it rules, it is said to be weakened (detriment).
Each sign is associated with one of the classical elements (fire, earth, air, or water) and one of the four modalities (cardinal, fixed, or mutable). It is also associated with an area of concern: personal, social, or universal.
Click on a button from the left menu to see descriptions of every zodiac sign.