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We began the month with a look at the constellation of Cassiopeia, the vain queen who inspired the wrath of Poseidon, so we will end it with a look at another constellation derived from that same myth: Pegasus, the winged horse.
In the Greek myth, the hero Perseus rode Pegasus to the shoreline to save Cassiopeia’s daughter, Andromeda, from Cetus, the sea monster unleashed by Poseidon. As such, Pegasus is another of the original 48 constellations listed in the 2nd century by the astronomer Ptolemy.
It is the seventh-largest constellation in the sky and is most easily spotted by the square that denotes the horse’s body, delineated by the stars Scheat, Markab, Algenib, and Alpheratz. From the northern hemisphere, the horse is upside down.
The chart shows the night sky looking south from London this week. On a clear dark night, look just beyond the head of Pegasus, marked by the star Enif, to see the small, faint constellation of Equuleus, the foal.
From the southern hemisphere, Pegasus is visible at this time of year leaping across the northern sky close to the horizon. The stars of Andromeda merge into Pegasus, serving as the horse’s hindlegs, as well as Cassiopeia’s beautiful daughter.