The constellation Pegasus, named after the mythical winged horse of Greek lore, was cataloged by the second-century astronomer Ptolemy and remains one of the 88 recognized modern constellations. Pegasus is recognizable as a celestial feature best viewed during the autumn months in the Northern Hemisphere. This article identifies the single star that shines brightest within its boundaries.
Locating the Pegasus Constellation
The easiest way to find Pegasus is by locating the famous asterism known as the Great Square of Pegasus, which represents the horse’s body. This large, distinctive square shape dominates the autumn sky and is formed by four bright stars. Three of these stars—Markab, Scheat, and Algenib—are officially part of Pegasus. The fourth corner of the square is marked by Alpheratz, a star that technically belongs to the neighboring constellation Andromeda. Pegasus is particularly high in the sky in the evenings throughout October, making it a reliable seasonal landmark for sky watchers.
The Brightest Star in Pegasus
The brightest star in the constellation Pegasus is Epsilon Pegasi, which is more commonly known by its traditional name, Enif. Enif is an orange supergiant star situated at the muzzle of the winged horse figure. Its apparent magnitude varies slightly between 2.37 and 2.45, making it the most luminous star visible from Earth within the constellation’s borders. Enif is a K-type supergiant, signifying a star that has exhausted the hydrogen fuel in its core and ballooned to an immense size. It is estimated to be roughly 690 light-years distant from our solar system, but its true luminosity is enormous, shining with the power of thousands of Suns.
Understanding Apparent Brightness
The reason Enif is the brightest star in Pegasus relates directly to the concept of apparent magnitude. Apparent magnitude is a measure of how bright a celestial object appears to an observer on Earth, determined by the star’s intrinsic luminosity and its distance from us. Astronomers use absolute magnitude to account for this distance factor, which measures a star’s brightness if it were placed at a standard distance of 10 parsecs (about 32.6 light-years). Enif’s tremendous size and power mean its absolute magnitude is quite high, even though it is hundreds of light-years away. This intrinsic brilliance allows Enif to maintain the lowest apparent magnitude number in Pegasus, surpassing the stars in the Great Square that are much closer to Earth.
Other Noteworthy Objects in Pegasus
Beyond its brightest star, Pegasus contains several other objects of significant astronomical interest. The globular cluster Messier 15 (M15), sometimes called the Great Pegasus Cluster, is a dense spherical collection of over 100,000 stars. This ancient cluster is one of the oldest known globular clusters in the Milky Way, visible with binoculars or a small telescope. The constellation is also home to Stephan’s Quintet, a visually striking group of five galaxies, four of which are gravitationally interacting. The fifth-magnitude star 51 Pegasi holds a unique place in history, becoming the first Sun-like star confirmed to host an exoplanet in 1995.