Pleiades (Greek mythology) Hesperides, nymphs of the morning star. After Atlas was forced to carry the heavens on his shoulders, Orion began to pursue all of the Pleiades, and Zeus transformed them first into doves, and then into stars to comfort their father. The constellation of Orion is said to still pursue them across the night sky. One of the most memorable myths involving the Pleiades is the story of how these sisters literally became stars, their "catasterism". According to some versions of the tale, all seven sisters committed suicide because they were so saddened by either the fate of their father, Atlas,
Ultimate fate of the universe cosmological constant, which would correspond to a negative energy density and positive pressure, would cause even an open universe to re-collapse to a big crunch. This option has been ruled out by observations. If the average density of the universe exactly equals the critical density so that formula_8, then the geometry of the universe is flat: as in Euclidean geometry, the sum of the angles of a triangle is 180 degrees and parallel lines continuously maintain the same distance. Measurements from Wilkinson Microwave Anisotropy Probe have confirmed the universe is flat with only a 0.4% margin of error. In absence