With an averageapparent visual magnitude of 2.4,[4] this is a second-magnitude star that is readily visible to the naked eye. The distance to this star can be estimated usingparallax measurements from theHipparcos astrometry satellite,[14][15] yielding a value of around 690light-years (210parsecs).[1]
ε Pegasi (Latinised toEpsilon Pegasi) is the star'sBayer designation.
It bore the traditional nameEnif derived from theArabic word for 'nose', due to its position as the muzzle of Pegasus. In 2016, theInternational Astronomical Union organized aWorking Group on Star Names (WGSN)[16] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[17] included a table of the first two batches of names approved by the WGSN; which includedEnif for this star.[18]
Other traditional names for the star includeFom al Feras, Latinised toOs Equi.[19] InChinese,危宿 (Wēi Sù), meaningRooftop (asterism), refers to anasterism consisting of Epsilon Pegasi,Alpha Aquarii andTheta Pegasi.[20] Consequently, theChinese name for Epsilon Pegasi itself is危宿三 (Wēi Sù sān, English:the Third Star of Rooftop.)[21]
Epsilon Pegasi is aslow irregular variable star that usually has a brightness between magnitudes 2.37 and 2.45. However, it was once observed very briefly at magnitude 0.7, giving rise to the theory that it (and possibly other supergiants) erupt in massiveflares that dwarf those of theSun.[24][25] It has also been observed as faint as magnitude 3.5.[24]
Based on its position on thecolor-magnitude diagram, Enif may have evolved from a whitish-yellow color to its current red color in the last 2,000 years, though there is currently no historical record supporting this.[7]
Epsilon Pegasi is a fine example to observe thePulfrich effect. This optical phenomenon is described on page 1372 ofBurnham's Celestial Handbook. According toJohn Herschel:The apparent pendulum-like oscillation of a small star in the same vertical as the large one, when the telescope is swung from side to side.[29]
^Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars".Astrophysical Journal Supplement Series.71: 245.Bibcode:1989ApJS...71..245K.doi:10.1086/191373.
^abcCousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards",South African Astronomical Observatory Circulars,8: 59,Bibcode:1984SAAOC...8...59C
^abcNeuhäuser, R; Torres, G; Mugrauer, M; Neuhäuser, D L; Chapman, J; Luge, D; Cosci, M (2022-07-29), "Colour evolution of Betelgeuse and Antares over two millennia, derived from historical records, as a new constraint on mass and age",Monthly Notices of the Royal Astronomical Society,516 (1):693–719,arXiv:2207.04702,Bibcode:2022MNRAS.516..693N,doi:10.1093/mnras/stac1969,ISSN0035-8711
^abSmith, Verne V.; Lambert, David L. (June 1987), "Are the red supergiants Epsilon Peg and 12 PUP victims of mild s-processing?",Monthly Notices of the Royal Astronomical Society,226 (3):563–579,Bibcode:1987MNRAS.226..563S,doi:10.1093/mnras/226.3.563
^Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities".Contributi Osservatorio Astronomico di Padova in Asiago.239 (1): 1.Bibcode:1970CoAsi.239....1B.
