Epsilon Pegasi, traditionally known as Enif, is the brightest star in the constellation Pegasus, shining at an apparent magnitude of roughly 2.4. That makes it a moderately bright star by naked-eye standards, easily visible from most locations on a clear night but not among the handful of showstoppers that dominate the sky. What catches many people off guard is that Enif is not part of the Great Square of Pegasus, the constellation’s most recognizable pattern, and it outshines every star in that famous asterism.
Enif Up Close
Enif is an orange supergiant star located about 690 light-years from Earth. Its spectral classification places it in the K-type range, meaning its surface temperature is cooler than the Sun’s, somewhere around 4,300 to 4,400 Kelvin compared to the Sun’s roughly 5,800 K. That cooler temperature gives it a distinct warm, orange hue that you can pick up with the naked eye if the sky is dark enough, and it becomes unmistakable through binoculars.
The “super” in supergiant is not an exaggeration. Enif has swelled to a diameter perhaps 150 times that of the Sun. If you placed it where the Sun sits, its outer layers would extend well past the orbit of Venus. It is also enormously luminous, pouring out thousands of times the energy the Sun does. Most of that output is in infrared wavelengths we cannot see, so its visual brightness actually understates how much energy it radiates.
The name Enif comes from the Arabic word for “nose,” because the star marks the muzzle of the mythological winged horse. In older star atlases you sometimes see the alternate spelling Fom al Feras, meaning “mouth of the horse,” which points to the same anatomical location. The International Astronomical Union formally adopted Enif as its proper name in 2016 as part of its ongoing effort to standardize star names across cultures.
The Great Square and Its Corner Stars
When most people picture Pegasus, they picture the Great Square, a large, slightly tilted rectangle of four stars that dominates the autumn sky in the Northern Hemisphere. Three of the square’s corners belong to Pegasus proper: Alpha Pegasi (Markab), Beta Pegasi (Scheat), and Gamma Pegasi (Algenib). The fourth corner, often labeled Delta Pegasi on older charts, is actually Alpha Andromedae, known as Alpheratz. Modern constellation boundaries place Alpheratz in Andromeda, not Pegasus, so it does not count when ranking the brightest stars in the winged horse.
Of the three Pegasus corners, Scheat is the brightest on average, hovering near magnitude 2.4 to 2.5 depending on when you observe it (more on that in a moment). Markab sits at about magnitude 2.5, and Algenib is the faintest corner at roughly 2.8. None of them quite matches Enif, which sits off to the west of the square, marking the horse’s head. The fact that the most prominent star in the constellation lies outside the most prominent pattern in the constellation is one of those quirks that makes learning star maps interesting rather than straightforward.
The interior of the Great Square is famously sparse. On a truly dark night, a sharp-eyed observer might count a handful of faint stars inside the square, but from suburban skies it looks almost empty. Astronomers sometimes use the square as a quick test of sky transparency: the more stars you can see inside it, the darker and clearer your sky.
Scheat and the Variable Star Complication
Scheat, Beta Pegasi, deserves its own discussion because it is a semi-regular variable star. Its brightness wanders between about magnitude 2.31 at its brightest and 2.74 at its faintest over irregular cycles lasting roughly 35 to 40 days. At peak brightness, Scheat actually edges out Enif. At minimum, Enif is clearly ahead. Averaged over time, Enif wins, which is why most references list Epsilon Pegasi as the constellation’s brightest star. But if you happened to look up on a night when Scheat was near maximum, you could be forgiven for thinking the square’s upper-right corner was the champion.
Scheat is a red giant with a surface temperature around 3,700 K, making it even cooler and redder than Enif. It lies much closer to us, only about 196 light-years away. Its variability comes from pulsations in its outer atmosphere: the star expands and contracts slightly, changing its surface area and temperature, which in turn changes how bright it appears. These pulsations are not perfectly periodic, so you cannot set your calendar by them the way you can with a classic Cepheid variable. That irregularity is part of what makes semi-regular variables tricky to characterize and easy to overlook.
The Other Bright Stars in Pegasus
Beyond Enif, Scheat, Markab, and Algenib, Pegasus contains a handful of other stars bright enough to trace out the horse’s body and legs under good conditions. Eta Pegasi (Matar) shines at about magnitude 2.9, making it the fifth-brightest star in the constellation. It is a binary system: the brighter component is a yellow giant, and the fainter companion is a main-sequence star. The pair orbits their common center of gravity over a period of roughly 813 days.
Mu Pegasi (Sadalbari) and Theta Pegasi (Baham) round out the constellation’s moderately bright members, both near magnitude 3.5. These are not stars most casual observers will notice, but they help flesh out the horse’s shape when you are tracing the full constellation rather than just the Great Square.
Pegasus also contains a number of double stars worth a look through a small telescope. For example, the star system near Enif includes a faint optical companion visible at low magnification. It is not a true binary (the two stars are not gravitationally bound), but the color contrast between Enif’s orange glow and the companion’s fainter hue makes for a pleasant view.
51 Pegasi and the First Exoplanet Around a Sun-Like Star
Ask an astronomer what makes Pegasus historically important, and they are as likely to mention 51 Pegasi as Enif. This unassuming star, at magnitude 5.5 and barely visible to the naked eye, became famous in 1995 when Michel Mayor and Didier Queloz announced they had detected a planet orbiting it. That planet, 51 Pegasi b, was the first exoplanet confirmed around a main-sequence, Sun-like star. The discovery earned Mayor and Queloz half of the 2019 Nobel Prize in Physics.
51 Pegasi is a G-type star about 50 light-years from Earth, making it close enough and bright enough that its spectrum could be studied with high precision. The planet that orbits it is a gas giant roughly half the mass of Jupiter, but it whips around the star in just over four days, sitting far closer to its host than Mercury does to the Sun. At the time, nobody expected giant planets to exist in such tight orbits, and the discovery launched an entirely new category of objects informally called “hot Jupiters.” The finding reshaped planetary science and opened the floodgates for the thousands of exoplanet detections that followed.
You can find 51 Pegasi on a clear night with binoculars by looking just west of the Great Square, though it takes a star chart or a smartphone app to pick it out from the surrounding field stars. It has no distinguishing color or brightness to make it stand out on its own.
How to Find Enif and Pegasus
Pegasus is an autumn constellation for Northern Hemisphere observers, reaching its highest point in the sky during October and November evenings. From southern latitudes, it appears lower in the northern sky during the same months but remains visible from most populated regions south of the equator.
The Great Square is the starting point. Face south (or north, if you are in the Southern Hemisphere) and look for a large rectangle of four roughly equal-brightness stars. The square is big, spanning about 15 degrees on a side, so it takes up a noticeable chunk of sky. Once you have identified it, Enif is about 12 degrees to the west-southwest of Markab, the lower-right corner of the square as seen from mid-northern latitudes. Think of the Great Square as the horse’s body and Enif as the tip of its nose stretching out to the right.
A useful trick is to start from the Summer Triangle, which is still high in the western sky during early autumn evenings. Draw a line from Altair in Aquila eastward, and you will pass close to Enif before arriving at the Great Square. Enif’s orange tint can help confirm you have the right star, especially through binoculars where colors pop more than they do to the naked eye.
Apparent Magnitude Versus True Luminosity
Ranking stars by brightness within a constellation uses apparent magnitude, which is how bright a star looks from Earth. This measure blends a star’s intrinsic luminosity with its distance from us and any intervening dust that dims its light. Astronomers correct for that dimming using dust maps of the Milky Way’s interstellar medium, an approach refined over decades to account for the patchy distribution of gas and dust along different sightlines through the galaxy.1Monthly Notices of the Royal Astronomical Society. A cold stellar stream in Pegasus
If you ranked Pegasus’s stars by absolute magnitude instead, which measures how bright a star would appear at a standard distance of about 33 light-years, the list would reshuffle. Enif, sitting nearly 700 light-years away, would become staggeringly bright at that standard distance, far outshining the others. Meanwhile, 51 Pegasi, which is a modest Sun-like star only 50 light-years away, would look even fainter than it already does at its current distance. Distance is doing a lot of work in determining which stars look bright and which do not.
For practical stargazing, apparent magnitude is all that matters. But understanding the distinction helps explain why Enif, a star most people have never heard of, is the champion of its constellation while sitting off to the side of the famous asterism. It is genuinely a powerful star, not just a nearby one enjoying favorable geometry.
Pegasus in Mythology and Mapping
The constellation represents the winged horse of Greek mythology, born from the blood of Medusa after Perseus beheaded her. In the sky, the horse is depicted upside down from the Northern Hemisphere’s perspective, with the Great Square forming its body and the legs extending upward and to the right. This inverted orientation confuses beginners who expect the horse to look like a horse standing on the ground. It does not. The head (marked by Enif) stretches out to the lower right, and the front legs dangle toward Aquarius and Pisces.
Pegasus is one of the 48 constellations catalogued by the Greco-Roman astronomer Ptolemy in the second century CE, and it survived essentially unchanged into the modern set of 88 constellations recognized by the International Astronomical Union. The main adjustment over the centuries was the reassignment of the northeast corner star, Alpheratz, from Pegasus to Andromeda, a change that formalized what had been an ambiguous double-listing for generations.
Deep-Sky Objects in the Pegasus Region
Pegasus is not typically the first constellation amateur astronomers turn to for deep-sky targets, but it holds a few gems. Messier 15 (M15) is a bright globular cluster located about four degrees northwest of Enif. At magnitude 6.2, it is visible through binoculars as a fuzzy spot and resolves into a dense ball of hundreds of thousands of stars through a moderate telescope. M15 is one of the most densely packed globular clusters known and lies about 33,000 light-years from Earth. It is also one of the oldest objects in the Milky Way, estimated at roughly 12 billion years old.
The constellation also hosts a handful of galaxies accessible to amateur telescopes. NGC 7331 is a spiral galaxy sometimes called the “Milky Way’s twin” because of its similar size and structure, though it sits about 40 million light-years away. Nearby in the sky, the group of galaxies known as Stephan’s Quintet became widely recognized after appearing in one of the first images released by the James Webb Space Telescope in 2022. Four of the five galaxies in the group are physically associated with one another at a distance of roughly 290 million light-years; the fifth is a foreground galaxy much closer to us that happens to line up with the others by coincidence.
For observers hunting deep-sky objects, starting at Enif and hopping to M15 is one of the easiest star-hop sequences in the autumn sky. The bright star serves as a convenient signpost, and the cluster lies close enough in the eyepiece field that finding one leads almost inevitably to the other. It is a fitting pairing: the constellation’s brightest star pointing the way to one of the sky’s finest globular clusters.