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Rh ortyx (= quail) and plunged into the sea to escape the love of Zeus. After her the Island of Delos was named Astĕria, and then Orty̌gia, till it received its ordinary name.

 Astræa (= star-maiden), was daughter of Astræus and Eōs, or, according to another account, of Zeus and Thĕmis, and as such was identified with Dĭkē. (See .) She lived among men in the golden age, and in the brazen age was the last of the gods to withdraw into the sky, where she shines as the constellation of the Virgin with her scales and starry crown.

 Astræus ( = star-man), son of the Titan Crius and Eury̌bĭa, father by Eōs of the winds Argēstēs, Zĕphy̌rus, Bŏrĕās and Nŏtus, as well as of Heōsphŏrus and the other stars. In the later legend he is also represented as father of Astræa.

 Astrology and Astronomy were at first synonymous expressions among the ancients, both signifying "the science of the stars." But afterwards Astrology came to mean that part of the science which deals with the supposed influence of the stars on the destinies of men. Among the Greeks, Astronomy, the origin of which they themselves ascribed to the Assyrians, Babylonians and Egyptians, was for centuries the subject of philosophical speculation without a sufficient groundwork in observation, because mathematics and mechanics had not reached the requisite degree of perfection. The list of observing astronomers opens with Eudoxus of Cnīdus in the first half of the 4th century,, who assumed that the earth was spherical, and tried to explain the phenomena of the heavens by a complicated theory of concentric spheres. Aristotle too maintained and proved the spherical form of the earth, which he took to be the immovable centre of the universe. Astronomy was first raised into a real science after 300 at Rhodes and Alexandria, in the Museum of which town the first observatory was built, and Aristyllus and Tīmŏchărēs determined the places of the fixed stars with comparative accuracy, though as yet with very rude apparatus. A great step in advance was taken by Aristarchus of Samos, who observed the summer solstice at Alexandria in 279, maintained the earth's rotation on her axis and revolution round the sun, and made an attempt, by no means contemptible, to ascertain the size and distance of the sun and moon. His successor Erătosthĕnēs also rendered essential their science; thus he came very near to determining the exact obliquity of the ecliptic. The true founder of scientific Astronomy, and the greatest independent observer of antiquity, was Hipparchus of Nicæa (in the 2nd century ), who discovered the precession of the equinoxes, and determined the length of the solar year (at 365 days 5 hours 55' 12”) as well as the time of the moon's revolution, and the magnitude and distances of the heavenly bodies. The last important astronomer of antiquity, and the greatest after Hipparchus, is Claudius Ptŏlĕmæus (in the 2nd century ). In his chief work, commonly known by its Arabic name of Almagest, he digested the discoveries of his predecessors, especially Hipparchus, and his own, into a formal system, which passed current all through the Middle Ages. According to it the earth is a sphere resting motionless in the middle of the equally spherical universe, while the sun, moon, planets and fixed stars roll at various distances around her.

The Romans regarded Astronomy as an idle speculation, and gave little attention to it. When Cæsar reformed the Roman Calendar, he had to bring an astronomer from Alexandria, Sōsĭgĕnēs, to help him.

Astrology in the narrower sense of the word, meaning prediction on the faith of signs given by the stars, was an invention of the Chaldæans. All but unknown to the Greeks in their best days, it did not come into vogue until after the time of Alexander the Great. In Rome the professional astrologers were called Chaldæi, or Măthēmătĭcī, the latter name referring to the astronomical calculations which they made. In the republican period they were known, but held in utter contempt. In 139 their unpopularity was so great that they were expelled from Rome and Italy. But in the turbulent times of the civil wars their reputation rose considerably, and still more under the Empire, when the most extensive demands were made upon their science. They were, indeed, repeatedly driven out of Italy and involved in trials for treason (māiestās); but this only enhanced the consideration in which they were held, the more so as they were frequently taken into counsel by the emperors and the members of the imperial family. In later times, all that the Chaldæans were forbidden to do was to consult the stars on questions referring to the emperor's life. This was a criminal offence. The Christian emperors (but none before them) issued