In Mesopotamian mythology, Gugalanna (lit. "The Great Bull of Heaven" < Sumerian gu "bull", gal "great", an "heaven", -a "of") was a Sumerian deity as well as a constellation known today as Taurus, one of the twelve signs of the Zodiac.[1]

Gugalanna was the first husband of the Goddess Ereshkigal, the Goddess of the Realm of the Dead, a gloomy place devoid of light, who was dispatched by Inanna to punish Gilgamesh for his sins. Gugalanna was sent by the gods to take retribution upon Gilgamesh for rejecting the sexual advances of the goddess Inanna. Gugalanna, whose feet made the earth shake, was slain and dismembered by Gilgamesh and Enkidu. Inanna, from the heights of the city walls looked down, and Enkidu took the haunches of the bull shaking them at the goddess, threatening he would do the same to her if he could catch her too. For this impiety, Enkidu later dies.

It was to share the sorrow with her sister that Inanna later descends to the Underworld.

Taurus was the constellation of the Northern Hemisphere Spring Equinox from about 3,200 BCE. It marked the start of the agricultural year with the New Year Akitu festival (from á-ki-ti-še-gur10-ku5, = sowing of the barley), an important date in Mespotamian religion. The "death" of Gugalanna, represents the obscuring disappearance of this constellation as a result of the light of the sun, with whom Gilgamesh was identified.

In the time in which this myth was composed, the New Year Festival, or Akitu, at the Spring Equinox, due to the Precession of the Equinoxes did not occur in Aries, but in Taurus. At this time of the year, Taurus would have disappeared as it was obscured by the sun.

http://en.wikipedia.org/wiki/Gugalanna