Enif (Epsilon Pegasi)
Enif (Epsilon Pegasi) is a star in the constellation Pegasus, magnitude 2.4.
The winged horse’s nose — an orange supergiant once caught in a startling flash.
Enif comes from the Arabic for “nose”: it marks the muzzle of Pegasus, the winged horse, and despite its epsilon label it is the constellation’s brightest star. Another old name, Fom al Feras, became Os Equi, “the horse’s mouth”, in Latin.
This is an orange supergiant of 11 to 12 solar masses, some 183 times the Sun’s width and about 8,500 times as luminous. In the Sun’s place it would reach past the orbit of Venus. Having used up the hydrogen in its core, it is almost certainly fusing helium now. It may end as a heavy oxygen–neon white dwarf, or in an electron-capture supernova.
Enif usually wavers only gently, but it once surprised observers by appearing very briefly at magnitude 0.7, far above normal — suggesting that supergiants may unleash huge flares. It may even have turned from whitish-yellow to its present colour within the last 2,000 years, though no historical record confirms it.
Enif (Epsilon Pegasi) is 690 light-years away: the light we see from it set off around 1335, 120 years before Gutenberg printed his Bible.
Did you know?
- The swinging star. Enif is a classic target for the Pulfrich effect: swing a telescope gently from side to side and a faint nearby star seems to sway like a pendulum against the bright one.
- Extra strontium and barium. Its spectrum shows an excess of strontium and barium, heavy elements that may be built up by slow neutron capture in the star.
- The Rooftop. In Chinese astronomy it is Wēi Sù sān, the Third Star of the Rooftop, an asterism shared with Alpha Aquarii and Theta Pegasi.
An orange 2nd-magnitude star marking the nose of Pegasus, well west of the Great Square at the end of the horse’s neck. Binoculars bring out its colour, and the globular cluster M 15 lies about four degrees to its north-west.
When and where to see it
It is best placed in the evening sky around September, when it crosses the meridian at about 10 pm local time (around midnight in August). It can be seen from everywhere north of 80°S and never sets north of 80°N.
At its highest it stands 50° up from 50°N, 65° up from 35°N, 80° up from the equator, 45° up from 35°S.
Facts
- Type
- Star
- Constellation
- Pegasus
- Designations
- Epsilon Pegasi, ε Peg, 8 Peg, HR 8308, HD 206778, HIP 107315
- Magnitude
- 2.4
- Position
- RA 21h 44.2m, Dec +9° 53′ (J2000)
- Spectral type
- K2Ib-II
- Colour
- orange-red (B−V 1.52)
- Distance
- 690 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Enif (Epsilon Pegasi) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.