Pegasus Constellation Guide — Stars, the Great Square, and How to Find the Winged Horse

How to Find Pegasus and the Great Square

Pegasus dominates the autumn sky, and its most recognisable feature — the Great Square — is one of the easiest asterisms to locate. The Great Square is formed by four stars: Scheat (Beta Pegasi), Markab (Alpha Pegasi), Algenib (Gamma Pegasi), and Alpheratz (Alpha Andromedae). Interestingly, Alpheratz is shared between Pegasus and Andromeda — it marks the top-left corner of the Great Square and also the head of the Andromeda constellation.

To find Pegasus, look high in the eastern sky during September and October evenings. The Great Square is roughly 15° across — about the width of one and a half clenched fists held at arm's length — and its stars are all magnitude 2.4–2.8, making them easily visible even from light-polluted suburban skies. The Square appears tilted on its side when first rising in the east, resembling a diamond more than a square. By midnight in October, it stands nearly overhead, oriented as a true square.

Once you have located the Great Square, the full Pegasus figure extends westward from it. Enif (Epsilon Pegasi), the constellation's brightest star at magnitude 2.4, marks the horse's nose, located about 20° west of the Square. The stars along the western edge form the horse's neck and head, while the Great Square itself represents the body. The constellation's full extent covers over 1,120 square degrees — the seventh-largest constellation in the sky.

Key Stars of Pegasus

The Mythology of Pegasus

In Greek mythology, Pegasus was the magnificent winged horse born from the blood of Medusa after she was slain by the hero Perseus. When Perseus cut off Medusa's head, Pegasus sprang forth fully grown, along with the warrior Chrysaor. Pegasus was later tamed by the hero Bellerophon, who rode the winged horse to defeat the Chimera — a fire-breathing monster with the head of a lion, the body of a goat, and the tail of a serpent.

After Bellerophon's successful adventures, he grew arrogant and attempted to fly Pegasus to Mount Olympus, the home of the gods. Zeus, angered by this hubris, sent a gadfly to sting Pegasus, causing Bellerophon to fall back to Earth. Pegasus continued to Olympus, where Zeus transformed him into a constellation, immortalising the winged horse in the night sky. The nearby constellations of Andromeda, Cassiopeia, Cepheus, and Perseus are all part of the same mythological cycle — making this region of the autumn sky a rich tapestry of interlocking stories.

Deep-Sky Objects in Pegasus

Pegasus lies in a region of sky away from the Milky Way's plane, so its deep-sky treasures are primarily galaxies and globular clusters rather than nebulae. The constellation rewards patient observers with several showpiece objects:

Observing Pegasus with Binoculars

Pegasus is an excellent constellation for binocular observers. The Great Square itself spans about 15°, which is too large for typical binocular fields (most 10×50 binoculars show about 6.5°), but scanning along the edges of the Square reveals a wealth of targets. M15 is easy to spot as a bright fuzzy patch near Enif. The variable star Scheat (Beta Pegasi) is worth monitoring — it is a semiregular variable that ranges between magnitude 2.3 and 2.8 over approximately 35 days, a variation easily detectable by comparing it with nearby Markab (magnitude 2.5).

One of Pegasus's most famous stars is 51 Pegasi — the first Sun-like star discovered to host an exoplanet. In 1995, astronomers detected 51 Pegasi b (unofficially named "Dimidium"), a hot Jupiter with a 4.2-day orbit. While the planet itself is invisible through any amateur telescope, the star (magnitude 5.5) is an easy binocular target about 3° south of the Great Square's western side. Knowing that this ordinary-looking star hosts the first exoplanet ever found around a main-sequence star adds a layer of significance to an otherwise unremarkable field of view. The discovery of 51 Pegasi b revolutionised astronomy — it proved that gas giant planets could exist in close orbits around their parent stars, challenging planet formation models and launching the modern era of exoplanet research.

Astrophotography Targets in Pegasus

Pegasus offers excellent astrophotography opportunities, particularly for imagers with moderate to large telescopes and tracking mounts. The constellation's deep-sky objects are predominantly galaxies, which respond well to long-exposure imaging with narrowband or broadband filters. The high altitude of Pegasus in autumn skies (near the zenith for northern hemisphere observers) means that atmospheric dispersion and light pollution are minimised, providing excellent imaging conditions.

NGC 7331 is the most photogenic galaxy in Pegasus for amateur astrophotographers. This unbarred spiral galaxy is oriented at a tilt that reveals both its bright core and spiral structure. At magnitude 9.5, it is bright enough to capture detail in 30–60 second exposures with a DSLR and 8-inch telescope. The galaxy's disc spans approximately 10 by 4 arcminutes, making it a well-framed target for moderate focal lengths (800–1200mm). The "Deer Lick Group" — a cluster of smaller companion galaxies including NGC 7335, 7336, 7337, and 7340 — appears in the same field of view, creating a stunning wide-field composition.

Stephan's Quintet is one of the most famous galaxy groups in the sky, thanks in part to its appearance in the film Interstellar. For astrophotographers, it presents a challenge: the five interacting galaxies span only about 8 arcminutes — a tight grouping requiring focal lengths of 1500mm or more to capture detail. Long exposures (5–10 minutes per subframe) reveal the tidal streams and distorted shapes caused by gravitational interactions between the galaxies. The bright foreground star NGC 7320 (a sixth galaxy that appears in the same line of sight but is actually a foreground object at 40 million light-years) adds visual interest to the composition.

For wide-field imagers using camera lenses or small refractors, the Great Square of Pegasus itself makes a striking framing element. The Square spans approximately 15° — easily captured with a 50mm lens on a full-frame camera. Including the Milky Way's autumn segment in the same frame creates a dramatic composition, with the Square acting as a celestial anchor for the surrounding star fields. The contrasting colours of Scheat (red giant, appearing orange) and Markab (blue-white main sequence star) add subtle colour variation to the wide-field view.