Pi2 Cygni

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Pi2 Cygni
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cygnus
Right ascension 21h 46m 47.61s
Declination +49° 18' 34.5"
Apparent magnitude (V) +4.23
Absolute magnitude (V) -3.52
Distance 1156 ly
(354.6 pc)
Spectral type B3III
Other designations
Sama al Azrak, 81 Cygni, HR 8335, HD 207330, BD+48 3504, FK5 821, HIP 107533, SAO 51293, GC 30512

Pi2 Cygni2 Cyg, π2 Cygni) is a fourth-magnitude star in the constellation Cygnus. It has the traditional name Pennae Caudalis, which is Latin for "Tail Feathers" (of Cygnus the Swan). Another name is Sama al Azrak (Arabic السماء الازرق ~ as-sama al-azraq), meaning "The Blue Sky".

In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of π2 Cygni, α Lacertae, 4 Lacertae, π1 Cygni, HD 206267, ε Cephei, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ψ Andromedae and ι Andromedae. Consequently, π2 Cygni itself is known as 螣蛇三 (Téng Shé sān, English: the Third Star of Flying Serpent)[1]


Pi2 Cygni is a spectroscopic binary with its main component being a Class B3 blue giant star with an apparent magnitude of +4.23 and a stellar luminosity nearly 2,200 times that of the Sun. This binary star system is approximately 1156 light years from Earth.