Pegasus (Winged Horse) & 51 Pegasi Guide

Sky Navigation & Astrophysical Context

Spanning 1,121 square degrees high across the northern autumn sky, Pegasus is the seventh-largest of the 88 IAU constellations and serves as the grand central station of autumn sky navigation. Its signature feature is the Great Square of Pegasus—a 15° × 15° box formed by Markab (Alpha Pegasi, +2.48), Scheat (Beta Pegasi, an M2.5 II-III red giant variable at +2.42), Algenib (Gamma Pegasi, +2.84), and Alpheratz (Alpha Andromedae, formerly Delta Pegasi). Extending southwest from Markab through Homam (Zeta Pegasi) and Biham (Theta Pegasi), the horse's neck ends at its brightest star: the K2 Ib orange supergiant Enif (Epsilon Pegasi, V = +2.39).

Pegasus stands at the absolute center of the modern exoplanet revolution: on October 6, 1995, Michel Mayor and Didier Queloz announced the radial-velocity discovery of 51 Pegasi b (Dimidium) orbiting the 5.5-magnitude solar twin 51 Pegasi (Helvetios) just north of Markab—the first exoplanet found around a main-sequence star, earning the 2019 Nobel Prize in Physics. Four years later in 1999, HD 209458 ('Osiris,' 7th magnitude near Enif) yielded the first planetary transit and the first atmospheric spectroscopy of an exoplanet; meanwhile HR 8799 provided the first directly imaged multi-planet system.

In deep-sky observing, 4.2° northwest of Enif shines Messier 15 (NGC 7078, V = +6.2), a dense core-collapsed globular cluster that houses both an intermediate-mass black hole candidate and the first planetary nebula ever identified inside a globular cluster (Pease 1), while north of the Great Square sit the unbarred spiral NGC 7331 (Caldwell 30) and the interacting galaxy group Stephan's Quintet.

Equatorial Center Position & Transit Altitude

Pegasus is centered near Right Ascension 22h 41m 24s, Declination +19° 28′ 12″ (The Winged Horse (Pegasus)).

Practical Star-Hopping & Observing Tips

• Use the western edge of the Great Square (Scheat through Markab) to point south toward Fomalhaut, and the eastern edge (Alpheratz through Algenib) to mark the Zero Hour (00h RA) equinoctial colure.
• Draw a line from Biham (Theta Pegasi) through Enif (Epsilon Pegasi) and extend it 4.2° northwest to center the blazing core of globular cluster Messier 15.
• Locate magnitude +5.49 51 Pegasi in binoculars halfway along the western edge of the Great Square between Scheat and Markab.

Notable Celestial Objects in & Near Pegasus

Scientific Sources Cited

• IAU Official Constellation Boundaries & Designations (IAU 88 Recognized Constellations): Delporte, E. 1930, Délimitation scientifique des constellations (IAU / Cambridge University Press) — International Astronomical Union (IAU)
• SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg