13 Zodiac and Explanation

Explanation from Raghunandan from the Planetary Society, India:

The order of the constellations of the Zodiac (as given by the apparent motion of the Sun over a year) starting with the Vernal Equinox and proceeding eastward along the Ecliptic is

Pisces	The Fishes	March	12	to	April	18
Aries	The Ram	April	19	to	May	13
Taurus	The Bull	May	14	to	June	19
Gemini	The Twins	June	20	to	July	20
Cancer	The Crab	July	21	to	August	9
Leo	The Lion	August	10	to	September	15
Virgo	The Maiden	September	16	to	October	30
Libra	The Balance	October	31	to	November	22
Scorpius	The Scorpion	November	23	to	November	29
Ophiuchus**	The Serpent-holder	November	30	to	December	17
Sagittarius	The Archer	December	18	to	January	18
Capricornus	The Goat	January	19	to	February	15
Aquarius	The Water-bearer	February	16	to	March	11

The Constellations of the Zodiac :

The ancients observed that the Sun, Moon and those 5 funny wandering stars (the planets known to the ancients) seem to be constrained to a particular region of the sky, never traveling really far north or south of a wide band of stars. They divided this sky band into 12 sections based on the old constellations, each differing in width but all of them about 16° high (+8°/-8°) and called them the “Zodiac”. Each division is named for the constellation situated within its limits in the 2nd century B.C.!

The name “Zodiac” is derived from the Greek, meaning “animal circle” (also related to the word “zoo”), and it comes from the fact that most of these constellations are named for animals, such as Leo, the Lion, Taurus, the Bull and Cancer, the Crab. It turns out that this band of the sky is centered on a line called the “ecliptic” which is the apparent path the Sun appears to take through the sky as a result of the Earth’s revolution around it (actually, it is defined as the projection the Earth’s orbital plane into outer space). If we could see the stars in the daytime, we would see the Sun slowly wander from one constellation of the Zodiac to the next, making one complete circle around the sky in one year. Which constellation the Sun was in had to be inferred by drawing all the constellations, then noting which was the last to set before sunrise and which was the first to rise after sunset then assuming the Sun was half way in between.