Pegasus is a northern constellation, named after the mythological Pegasus. It is one of the 88 modern constellations, and was also one of the 48 constellations listed by Ptolemy.
Notable features
α Peg (Markab), β Peg, and γ Peg, together with Alpheratz (α Andromedae) form the large asterism known as the Square of Pegasus. A star in this constellation, 51 Pegasi, is orbited by the first true extrasolar planet (planets orbiting a star other than the Sun) to have been discovered.
Notable deep sky objects
History and mythology
Pegasus has an appearance resembling a grazing horse, with a large square area as its body [1]. Due to the presence of the 4 brightest stars in the square, i.e. the 4 horses of pegasus, this may be part of the origin of the myth of the Mares of Diomedes, one of The Twelve Labours of Herakles, together with another feature in the Zodiac sign of Aquarius, namely Aquarius itself, pouring out the waters.
The star Alpheratz, one of the 4 stars in Pegasus' square, was later considered to be part of Andromeda. By moving the star, the square became a triangle attached to a stick body, thus resembling a wing. As a winged horse, Pegasus features in Greek mythology as its namesake, Pegasus.
Visualization
Pegasus' brightest stars (of the second magnitude) are Alpha Pegasi and Beta Pegasi, which together with Gamma Pegasi (third magnitude) form the triangular wing of the horse.
The body of the horse consists of a quadrilateral formed by the stars Alpha Pegasi, Lambda Pegasi, Iota Pegasi, and Xi Pegasi.
The front legs of the winged horse have two stars of the fourth magnitude which have no Bayer designations but which do have Flamsteed numbers: 1 Pegasi and 9 Pegasi.
The stars Epsilon Pegasi and Theta Pegasi belong to the hind legs, with Epsilon Pegasi being of the third magnitude. Rho Pegasi and Sigma Pegasi belong to the tail, but they are both dim: of the fifth magnitude.
Eta Pegasi and Pi Pegasi form the head: Pi Pegasi is the snout, and Eta Pegasi has magnitude three. Mu Pegasi is the beginning of the neck.