Pegasus
Pegasus, the winged horse that forms the "Great Square," the landmark of the autumn sky. It was born from the blood of Medusa.
Science
The scienceThe four brightest stars of Pegasus trace a great square in the sky — the "Great Square of Pegasus (the Great Square of Autumn)" — a landmark for finding one's bearings in the autumn sky, where bright stars are scarce. Curiously, the star at the upper-left corner of the square, Alpheratz, actually belongs to neighboring Andromeda. The inside of the square looks so empty of noticeable stars that it is even used as a gauge of dark skies. Near Enif, the star of the neck, lies the beautiful globular cluster M15.
Mythology
How it became a constellationPegasus is the winged horse that sprang from the blood of Medusa when the hero Perseus struck off her head. This white steed, roaming freely through the sky, was later tamed and ridden by the hero Bellerophon, who slew the monster Chimera. But when Bellerophon grew arrogant and tried to ride Pegasus all the way up to Olympus, the home of the gods, Zeus sent an insect to sting the horse's back and threw him off. Pegasus rose to the heavens alone, became the horse that bears Zeus's thunderbolts, and at last remained as a constellation.
Observing Guide
how to observe🔭 How to find it
In the autumn sky, first find the large square of four bright stars in the southeast — the "Great Square of Autumn," also known as the Great Square of Pegasus. This square is the winged horse's body; from its upper-left corner star, Alpheratz, you can follow the chain of stars through Andromeda all the way to Perseus. Off the right (western) side of the square, the stars of the neck and nose extend outward, ending at the bright star Enif, the horse's muzzle.
✨ What to look for
Pegasus's crown jewel is the globular cluster M15, near the neck star Enif — hundreds of thousands of stars packed unusually tightly toward the center, so bright it appears as a distinct cottony ball even in a small telescope, making it one of the Northern Hemisphere's premier globulars. There's also "Stephan's Quintet" (near NGC 7331), a group of overlapping galaxies that's a popular astrophotography target, though it's quite faint for visual observation.
📍 Where to see it (US · Canada · UK · Australia)
Spanning declinations of +10° to +30°, Pegasus is a classic autumn constellation. From the US, Canada, and the UK the Great Square hangs high in the southern sky on evenings from September through November, serving as a signpost around the sparse autumn stars. From Australia it appears low to middling in the northern sky during the southern spring, hanging upside down relative to the northern view.