“Astraea’s themes are excellence, learning, purity, justice, knowledge, reason and innocence. Her symbols are stars. This Greek Goddess motivates fairness and virtue within us. She empowers our ability to ‘fight the good fight’ in both word and deed, especially when we feel inadequate to the task. According to lore, She left earth during the Iron Age because of man’s inhumanity to man. She became the constellation Virgo.
In astrology, people born under the sign of Virgo, like Astraea, strive endlessly for perfection within and without, sometimes naively overlooking the big picture because of their focus on detail. Astraea reestablished that necessary perspective by showing us how to think more globally. To encourage this ability, draw a star on a piece of paper and put it in your shoe so that your quest for excellence is always balanced with moderation and sound pacing.
To meditate on this Goddess’s virtues and begin releasing them within, try using a bowl (or bath) full of soapsuds sprinkled with glitter (this looks like floating stars) as a focus. Light a candle nearby and watch the small points of light as they dance; each one represents a bit of magical energy and an aspect of Astraea. Tell the Goddess your needs and your dreams, then float in Her starry waters until you feel renewed and cleansed.”
(Patricia Telesco, “365 Goddess: a daily guide to the magic and inspiration of the goddess”.)
Astraea (“the star maiden”) was a daughter of Themis and Zeus, “She lived on earth in the Golden Age when all lived in peace together. But as humankind grew more and more violent, the gods abandoned this world and retreated to the heavens. Patient and hopeful, Astraea was the last of the immortals to leave, but finally even She was forced to abandon the earth” (Monaghan, p. 57).
“Fleeing from the new wickedness of humanity, She ascended to heaven to become the constellation Virgo the scales of justice She carried became the nearby constellation Libra, reflected in Her symbolic association with Justitia in Latin culture. In the Tarot, the 8th card, Justice, with a figure of Justitia, can thus be considered related to the figure of Astraea on historical iconographic grounds.
According to legend, Astraea will one day come back to Earth, bringing with Her the return of the utopian Golden Age of which She was the ambassador.
Astraea is always associated with the Greek Goddess of justice, Dike, who used to live on Earth but left, sickened by human greed. Astraea is sometimes confused with Asteria, the Goddess of the stars and the daughter of Koios and Phoebe.” 
Monaghan, Patricia. The New Book of Goddesses and Heroines, “Astraea”.
Gods-and-monsters.com, “Astraea of Greek Mythology“.
Theoi Greek Mythology, “Astraea“.