ince Macedonia abounds with myths, and the river Astraeus is no exception, I thought I would add something about the background to the names in the area. The mythology backs up Aelian's view that the Astraeus was near Borea, if you read the following tale. Much of my writing is condensed from the wonderful Encyclopaedia Mythica and the graphic is reproduced with their permission - it is well worth dropping in there, but only if you have a lot of time to spare - be warned, this is a fascinating site!
Professor Hammond's view is that "...there was a nymph Astraea, appropriate to a river of her name, 'Astraeus,' and that she was selected as the nurse of the lady Beroe, the patroness of Beroea...' which is the most likely reason for the river acquiring its name. According to Encyclopaedia Mythica:
Astraea ("the star-maiden") is the daughter of Zeus and Themis. She was, as was her mother, a goddess of justice. During the Golden Age, when the gods dwelled among mankind, she lived on the earth. When evil and wickedness increased its grip on humanity, the gods abandoned the habitations of mankind. Astraea was the last to leave and took up her abode among the stars where she was transformed into the constellation Virgo.
Pretty good stuff, huh? However, there is another candidate from whom the river might have got its name, if you read on below.
Eos, in Greek mythology, was the goddess of dawn and the sister of Helios, the Sun, and Selene, the Moon. Her husband was Aeolus, sometimes known as Astraeus, by whom she bore the stars and the winds: Notus, the south wind; Boreas, the north wind; Euras, the east wind; and Zephyr or Zephyrus, the west wind. But because Eos slept with Ares, Aphrodite turned her into a nymphomaniac. There were much worse curses, and Eos seems to have a reasonably good time after this; among her many lovers were Tithonus, Cephalus and Orion.
Astraeus was a minor deity, the son of a king called Hippotes. He kept the winds in huge caves on the island of Aeolia. In one myth, Astraeus is said to have given a bag of winds to Odysseus, to help the latter on his way home, but Odysseus' crew opened the bag while he slept and all the winds escaped.
Boreas had two sons, two daughters and possessed twelve magical mares which could race across the ground without destroying the crops. When the Persian navy of Xerxes attacked Athens, the Athenians begged for his assistance and Boreas whipped up a storm, which sank 400 Persian ships.
Useful, these gods, but never around when you need them, in my experience.