Pegasus, the celestial winged horse of Greek mythology, is one of the largest and most easily recognized constellations in the night sky. This northern constellation, first cataloged by the astronomer Ptolemy in the 2nd century, occupies a vast area of the celestial sphere. While often associated with the Great Square asterism, the constellation contains many stars, with one standing out as its brightest beacon.
Identifying the Brightest Star
The brightest star within the official boundaries of the Pegasus constellation is Enif, also designated Epsilon Pegasi. This orange supergiant shines with an apparent visual magnitude typically around 2.39, making it easily visible to the naked eye. The three stars defining the Great Square asterism—Markab, Scheat, and Algenib—are all slightly fainter than Enif.
The star Alpheratz, which completes the Great Square, is brighter than Enif but is officially part of the neighboring Andromeda constellation. Although Alpheratz was historically known as Delta Pegasi, modern astronomical boundaries established by the International Astronomical Union confirm Enif as the brightest star belonging to Pegasus.
Stellar Characteristics of Enif
Enif is a massive, highly evolved K2 Ib supergiant that has dramatically expanded after leaving the main sequence. Its surface temperature is relatively cool (around 4,300 Kelvin), giving the star its characteristic yellowish-orange color.
Located approximately 690 light-years from Earth, Enif possesses a radius about 185 times that of the Sun. It radiates energy equivalent to roughly 12,000 times the Sun’s luminosity, making it the brightest object in the constellation.
With a mass about 12 times that of the Sun, Enif is nearing the end of its stellar life, having exhausted its core hydrogen fuel. Its ultimate fate is uncertain, potentially ending as a massive white dwarf or a spectacular electron-capture supernova. Enif is also an irregular variable star, exhibiting small, unpredictable fluctuations in brightness.
Locating the Pegasus Constellation
Pegasus is most easily found by locating the Great Square of Pegasus, a large, nearly perfect asterism that represents the horse’s torso. The square is formed by the stars Markab, Scheat, and Algenib, along with Alpheratz from Andromeda.
The constellation is best observed high in the sky during the autumn and early winter months in the Northern Hemisphere, with October being the peak viewing time. This recognizable pattern is a useful tool for star-hopping to other constellations like Andromeda and Pisces.
Enif, the brightest star, is situated away from the main square, marking the muzzle or nose of the winged horse figure. It extends from the corner star Scheat, allowing observers to trace the head and neck of the constellation and appreciate the star’s distinct orange hue.