The astronomical science of the Babylonians thus resolves itself into these natural divisions:
(1) the constellations, especially those of the zodiac,
(2) the five great planets,
(3) the fixed stars, Anu, Bel, and Ea,
(4) miscellaneous stars, and
(5) the sun and moon.
The rivalry between the two great luminaries ends in a superior rank being accorded to the sun. Natural and indeed inevitable as this conclusion was, the scientific theory in the Euphrates Valley was presumably influenced to some extent by the circumstance that the head of the pantheon was a solar deity. We have seen that the tradition of this original character of Marduk survived in the popular mind.
Of the sun but little need be said here. As represented in the creation story, he was freer in his movements than any of the planets. He passed across the heavens daily as an overseer to see that everything was maintained in good order. As in Greek mythology, the sun was represented as riding in a chariot drawn by horses.[825] Scientific speculation advanced but little upon these popular fancies. The course that the sun took on the ecliptic was determined, and the ecliptic itself served as the guide for determining the position and movements of the stars. Under the growing influence of the Marduk cult and of such deities as Ninib, Nergal, and Nabu, associated with Marduk mythologically or politically, the old moon worship lost much of its prestige; but in astronomical science, the former independent rank of the moon is still in large measure preserved. In the enumeration of the planets the moon is mentioned first.[826] The moon is not a 'sheep' belonging to the flock of Shamash. The importance of the moon in the regulation of the calendar saved her from this fate. The beginning of the calendrical system, indeed, may well have been of popular origin. Ihering[827] is of the opinion that agricultural occupations made the marking off of time a popular necessity, and this view is borne out by the early epithets of the months among the Babylonians,[828] which, as among the Hebrews, are connected with agriculture and the life of the agriculturist. The later names also bear traces of the same train of thoughts. Leaving aside details into which it is needless to enter here, the part of the calendar which touches upon the religion of the Babylonians is the sacred character given to the months by making each one devoted to some god or gods. In this association there may be observed the same curious mixture of several factors that controlled the identification of the planets with the gods. The theory underlying the pantheon and certain mythological conceptions are two of the factors that can be clearly seen at work. The triad Anu, Bel, and Ea are accorded the first rank.[829]
The first month, Nisan, is sacred to Anu and Bel.
The second, Iyar, is sacred to Ea as the "lord of humanity."