Meet Enif, a supergiant star and the brightest member of the Pegasus constellation. Find out more about this star and its place in our skies.
|Other designations||Epsilon Pegasi, HIP 107315, HD 206778, HR 8308|
|Distance from Earth||690 light-years|
|Right ascension||21h 44m 11s|
|Declination||+09° 52' 30”|
|Exoplanets status||None known|
|Probable fate||Likely supernova|
Sometimes a particular aspect of a constellation becomes more famous than the whole. This is certainly the case with Orion and Ursa Major, where the three-star belt and the Big Dipper far out-fame other features in these sprawling constellations.
A similar situation occurs in Pegasus; the famous summer square is easy to remember and makes a great conversation piece, but what about the rest of the horse? You might only have a vague memory map of the horse’s legs and head, and when was the last time you actually went looking for the rest of the constellation?
You should, because if you don’t, you’re actually missing out on the prime jewel of the flying horse — the constellation’s brightest star, known as Epsilon Pegasi, or Enif.
Enif is an orange supergiant star that began to grow as its internal nuclear fuel reserves ran short, and it began to combine heavier elements. The growth is real in terms of diameter — Enif’s sphere is a fantastic 185 times wider than the Sun — but since there is no actual new mass being added, Enif has simply become more diffuse.
Naturally, Enif cools off as it pushes out (think of spreading out hot mashed potatoes to cool them faster). The more a star cools off, the more its color shifts toward red, giving Enif the obvious orange color we see today.
What its diffuse nature does not minimize however is Enif’s light output, as the star shines with a staggering luminosity of 5,000 Suns due to the large surface area. Bigger often, though not always, means brighter when it comes to stars. If Enif could replace the Sun in our solar system, sunglasses would surely not be enough.
But becoming a supergiant star isn’t without its accompanying growing pains. We’re used to the Sun’s steady and reliable output of consistent energy, but supergiants like Enif tend toward instability, sometimes dimming (like Betelgeuse did in 2020) or sometimes brightening significantly. Enif has done both, historically.
Remember that in astronomy, star brightness is measured on a logarithmic magnitude scale that operates reversed from what you might expect. Brighter stars have lower numbers, even negative ones (Sirius shines at -1.5), while fainter stars have larger numbers. In the case of Enif, it typically varies in brightness between 2.29 and 2.44, but faded to a dim 3.5 in November 1847. There was also a short period of extreme brightening in September 1972, when Enif briefly appeared at an amazing 0.7! Paying attention to and looking for these types of events is a way that amateur astronomers can contribute to real science.
Origin / Mythology
Modern stargazers have no reason to be confused about the intended structure of the Pegasus constellation. The star’s name Enif was given it by ancient Arab astronomers, and means “nose,” clearly indicating its position on the tip of Pegasus’s muzzle. (The true origins are probably even older, going back to ancient Mesopotamia). The Greeks shared this interpretation, and it’s the one official used by astronomers today.
But not all cultures across time have included Enif with the stars of Pegasus, possibly because Enif isn’t terribly close to the Great Square. Chinese astronomers included Enif in a constellation called the “Roof Mansion,” one of 28 such astronomical houses, and it was named 危宿三 (Wēi Sù sān, “the Third Star of Rooftop.”
Japanese star mythology included Enif in a string of small constellations sitting roughly along the ecliptic known as lunar lodges, presumably since the Moon could be seen passing through them each month. Dakota/Lakota and Ojibwe North American Indian tribes viewed the Great Square as either a turtle or a moose, and didn’t include Enif at all.
How to See Enif
Pegasus is an excellent autumn constellation, taking center stage in the eastern sky after dusk, While the Great Square is naturally the most obvious portion of the constellation, Enif is actually the brightest star in the constellation at 2.39 (surprising, given that it’s named after the fifth letter of the Greek alphabet rather than the first). Like Rudolph the Reindeer, Pegasus indeed has a “very shiny nose.”
There are no precise pointer stars to get you to Enif; it’s just a matter of starting at the Great Square and working west to the only 2nd-magnitude star in the vicinity. If you imagine a second Great Square just west of the first one, Enif would represent the lower right-hand corner.
When trying to visualize the constellation, keep in mind that only the front half of Pegasus is generally implied, much like Taurus the Bull. Also, remember that the entire horse will be upside-down when viewed from the Northern Hemisphere.
If you live in the Northern Hemisphere and absolutely insist on a view of Pegasus facing upright, you’ll need to take a vacation some distance below the equator, where Pegasus appears in the correct orientation, though now flipped left-to-right. (In a budget-friendly pinch, rotating a photograph 180° can also suffice.)
Enif can act as a gateway to point you towards a fun but faint constellation you may have never seen. A small hop west brings you to tiny Equuleus, which represents a foal belonging to Pegasus. This time, the constellation is just a face portrait of the little horse, with Enif, the muzzle of his parent, reaching out towards his foal.
Finally, if you examine Enif with a telescope, you’ll notice a very close pairing with a fainter star. This is just a line-of-sight visual pair; Enif, like so many other enormous reddish stars, is actually alone. But even without the telescope, the orange/red color is easy to see once you know what you’re looking for. Why not try tonight?
Daniel Johnson is a Wisconsin-based freelance writer, professional photographer, and coauthor of more than a dozen books. He’s a longtime amateur astronomer and fortunate enough to live in a rural region with excellent seeing conditions. You can view some of Dan’s photography at www.foxhillphoto.com.