Astarte is the sex goddess of the sun god Baal and is also called "the queen of heaven" in Jer. 7:18 and 44:17-25.
The Dictionary of Mythology, Folklore, and Symbols, Part 1, page 487 tells us more about this Spring Festival:
‘‘It incorporates some of the ancient Spring Equinox ceremonies of sun worship in which there were phallic [genital] rites and spring fires, and in which the deity or offering to the deity was eaten...The festival is symbolized by an ascension Lily...a chick breaking its shell, the colors white and green, the egg, spring flowers, and the Rabbit. The name is related to Astarte, Ashtoreth, Eostre and Ishtar, goddess who visited and rose from the underworld. Easter yields ‘Enduring Eos’...‘Enduring Dawn’.’’
We learn about these Temple Prostitutes from The Interpreter’s Dictionary of The Bible, Volume 3, pages 933-934:
"The role of the sacred prostitute in the fertility cult: The prostitute who was an official of the cult in ancient Palestine and nearby lands of biblical times exercised an important function. This religion was predicated upon the belief that the processes of nature were controlled by the relations between gods and goddesses. Projecting their understanding of their own sexual activities, the worshipers of these deities, through the use of imitative magic, engaged in sexual intercourse with devotees of the shrine, in the belief that this would encourage the gods and goddesses to do likewise. Only by sexual relations among the deities could man’s desire for increase in herds and fields, as well as in his own family, be realized. In Palestine the gods Baal and Asherah were especially prominent. These competed with Yahweh the God of Israel and, in some cases, may have produced hybrid Yahweh-Baal cults. Attached to the shrines of these cults were priests as well as prostitutes, both male and female. Their chief service was sexual in nature, the offering of their bodies for ritual purposes.
Many believe that this was the whoredoms into which Gomer, wife of Hosea, was lured. From which he redeemed her and to which she kept returning.
The Old Testament furnishes abundant evidence as to the character of the religion of the land into which the Israelites came. Fertility rites were practiced at the numerous shrines which dotted the land, as well as at the major sanctuaries. The Israelites absorbed the Canaanite ways and learned to identify their god with Baal, whose rains brought fertility to the land.