Constellations have served many different purposes throughout the years. Because they appear in the sky at specific locations during different times of the year, constellations have been used to:
Remind farmers to plant and harvest crops.
Help travelers navigate through deserts and across oceans.
Used to represent heroes and mythical creatures that have been the subjects of folk tales down through the generations.
There is also a constellation for each sign of the zodiac, which tracks the Earth's orbit around the sun as it is experienced in the Northern Hemisphere. The 12 constellations of the zodiac lie along the path of the orbit, which is known as the ecliptic.
It takes the earth a year to circle the sun, and each zodiac sign or constellation of the zodiac corresponds to a monthlong portion of the calendar year. Ophiuchus, the 13th constellation on the ecliptic, is not part of the zodiac because when the signs were first described, the stars were not in the same position as they are today!