Magnitude 4.66 Apparent magnitude (V) 4.66 | Constellation Cygnus | |
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Pi1 Cygni (π1 Cygni, abbreviated Pi1 Cygni, π1 Cygni), also named Azelfafage, is a binary star system in the northern constellation of Cygnus. It is visible to the naked eye, having a combined apparent visual magnitude of 4.66. The distance to this system can be roughly gauged by its annual parallax shift of 1.89 mas, which yields a separation of around 1,700 light years from the Sun, give or take a hundred light years.
This is a single-lined spectroscopic binary with a close, circular orbit, having a period of just 26.33 days. The primary, component A, is a slightly evolved B-type subgiant star with a stellar classification of B3 IV. It has an estimated 10 times the mass of the Sun and around 5.6 times the Sun's radius. The star radiates 16,538 times the solar luminosity from its outer atmosphere at an effective temperature of roughly 18,360 K. It is about 25 million years old and is spinning with a projected rotational velocity of 55 km/s.
Nomenclature
π1 Cygni (Latinised to Pi1 Cygni) is the star's Bayer designation. It is also designated HIP 107136 and HR 8301
It bore the traditional name Azelfafage, derived from the Arabic ظلف الفرس Dhilf al-faras meaning "the horse track" or (probably) ذيل الدجاجة Dhail al-dajājah meaning "the tail of hen". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Azelfafage for this star on 12 September 2016 and it is now so entered in the IAU Catalog of Star Names.
In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of Pi¹ Cygni, Alpha Lacertae, 4 Lacertae, Pi² Cygni, HD 206267, Epsilon Cephei, Beta Lacertae, Sigma Cassiopeiae, Rho Cassiopeiae, Tau Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, Lambda Andromedae, Kappa Andromedae, Psi Andromedae and Iota Andromedae. Consequently, Pi¹ Cygni itself is known as 螣蛇四 (Téng Shé sì, English: the Fourth Star of Flying Serpent)