The Zodiac

The zodiac is a twelve-part division of the sky in the neighbourhood of the ecliptic. We can imagine this as a wide band stretched around the celestial sphere, and cut in half by the orbit of the Sun, as shown in the diagram below. In astrology, these twelve parts are called signs. Each of these parts has a size of 30°.



A common misconception is to term the signs as “constellations”. The twelve signs used by the astrologers are not the same as the 88 constellations in observational astronomy. The constellations are by definition a pattern of stars, and their sizes differ greatly. The signs, on the other hand, are pure geometrical constructs.

As the Sun makes its annual path around the ecliptic, it resides in each of the twelve signs, in turn. An individual born during a certain time would take on the sign the Sun is in at that moment. This is called the “sun sign” of the horoscope. The individual is then supposed to take on the characteristics associated with the sign.