Pictures in the Sky
As you gaze towards the heavens, you can see that some stars form objects or pictures. These are called Constellations. Ptolemy, a 2nd century Greek astronomer, cataloged 48 constellations that are still recognized today. There are 88 constellations that are recognized by the International Astronomical Union or IAU.
There are 12 of these constellations that follow an imaginary line called the "Ecliptic". The Ecliptic is the apparent path of the Sun through the sky. As the earth moves along its orbit around the sun, the tilt makes the ecliptic change. This is why the sun rises and sets in different parts of the sky at different times of the year. This is also why the length of day and night change throughout the year.
Back to the Zodiac Constellations...
The ancient Greeks called the ecliptic "zodiakos kyklos, "circle of animals," or ta zodia, "the little animals." This was because most of the constellations through which the ecliptic passes represent animals. The size of the constellations varies so the sun could spend more time in one and less in another.
With the onset of mathematical astronomy, the sky was divided into 30deg sections. This way, the sun is in each section the same amount of time. The list below shows the zodiacal constellations and the dates of the sun's passage through them. These dates are still used for the astrological signs, however due to precession, the movement of the sky in relation to Earth, their positions have shifted the constellations eastward. For example, the sun is within the 30deg section of Taurus, but the date says it should be in Gemini.
Aries- March 21 thru April 19
Marks the Vernal Equinox, the beginning of the summer season in the northern hemisphere.
The constellation of Aries is the Ram in Greek mythology.
Taurus- April 20 thru May 20
The constellation of Taurus is the Bull in Greek mythology. Zeus transformed himself into this bull to abduct the maiden Europa. He swam her to Crete where she had a son, Minos. Thrilled with this, Zeus added the bull, Taurus in the heavens.
Gemini- May 21 thru June 20
The constellation of Gemini are the Twins, Castor and Pollox in Greek mythology
Cancer- June 21 thru July 22
The constellation of Cancer represents the Crab in Greek mythology. Cancer was killed by Heracles while trying to kill Hydra, the water snake.
Leo- July 23 thru August 22
The constellation of Leo represents the Nemean Lion
Virgo- August 23 thru September 22
The constellation of Virgo represents the Maiden. This signifies the ripening of the grapes and readiness to be made in to wine.
Libra- September 23 thru October 22
Marks the Autumnal Equinox, the beginning of fall in the northern hemisphere.
Libra is referred to the Scales (of justice).
Scorpio- October 23 thru November 21
This constellation represents the scorpion that killed Orion the Hunter.
Libra was once part of Scorpius, and referred to as the "claws".
Sagittarius- November 22 thru December 21
This constellation represents an Archer. He is a centaur, a half man half horse creature. It is home to the "Teapot" asterism. Also very close to the center of the Milky Way galaxy.
Pisces- February 19 thru March 20
This constellation represents the "Fishes". The mother and son duo of Aphrodite and Eros.
Aquarius- January 20 thru February 18
This constellation represents the "Water Bearer". A servant to the gods, abducted by Zeus.
Capricorn- December 22 thru January 19
The constellation of Capricorn is the "Goat Horn" or "Sea Goat". A "brother" to Zeus, was known to blow his conch shell before battle with the Titans.