Zodiac in Astronomy
History of the Zodiac
The zodiac comes from the Greek zoidiakos which means the mark of a small animal. In Latin this word becomes zodiacus. Zodiac itself is defined as a constellation of stars visible from the earth crossed by the sun every year.
The classic zodiac is divided into 12 constellations.
In the past, sky-watchers often made an imaginary line between stars that later formed a constellation that had certain features such as a lion for the Leo constellation. Well, they not only group the stars into a constellation but also divide the ecliptic (the area that the Sun passes in its annual cycle) into 12 areas with the same magnitude of 30 degrees.
The twelve areas were then filled by one constellation known as the Zodiac Constellation. If the Sun moves at the same rate then it will enter a new constellation every 30 days so that it can be said that the Sun will be in every constellation for 30 days or one constellation for 1 month starting with the Sun position in Vernal Equinox, which at that time is the time of the Sun are in the constellation Aries. The 12 constellations are: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces
This division of the area facilitates the work of sky observers to record the position of the Sun, Moon and the planet with the reference point of the stars. And this system became the first sky coordinate system created and then developed into the coordinate system that we know today (equatorial coordinate system).
This division was first made by the Babylonians in the early / mid millennium BC (626 BC - 539 BC). The zodiac also derives from a modified MUL.APIN catalog containing 200 astronomical observations including measurements related to several constellations. MUL.APIN catalog system is believed to be made in the range 1370 BC but there are also sources that mention the circa 1830 BC.
This Babylonian star catalog later entered Greek astronomy in the 4th century BC and was later used by the Romans. This zodiac description then appears in Al Magest Star Catalog (130-170 AD) compiled by Ptolomy of Alexandria in describing his geocentric theory.