Star system in the constellation Cygnus
For other stars with this Bayer designation, see
π Cygni .
Pi2 Cygni Location of π
2 Cygni (circled in red)
Observation dataEpoch J2000.0 Equinox J2000.0 (ICRS ) Constellation Cygnus Right ascension 21h 46m 47.60832s [ 1] Declination +49° 18′ 34.4511″[ 1] Apparent magnitude (V)4.24[ 2] Characteristics Spectral type B2.5 III[ 3] U−Bcolor index −0.79[ 2] B−Vcolor index −0.125[ 2] Variable type β Cep [ 4] Astrometry Radial velocity (Rv )−12.3[ 5] km/s Proper motion (μ)RA: +2.77[ 1] mas /yr Dec.: −2.00[ 1] mas /yr Parallax (π)2.95± 0.34 mas [ 1] Distance approx. 1,100 ly pc ) Absolute magnitude (MV )−3.39[ 6] Orbit [ 7] Period (P)72.0162 d Eccentricity (e)0.34 Periastron epoch (T)2428410.6 JD Argument of periastron (ω)238.1° Semi-amplitude 1 )7.8 km/s Details π2 Cyg A Mass ± 0.4[ 8] M ☉ Radius 7.1[ 9] R ☉ Luminosity (bolometric) 8,442[ 10] L ☉ Surface gravity (log g )± 0.16[ 11] cgs Temperature ± 1,057[ 11] K Metallicity [Fe/H] ± 0.09[ 11] dex Rotational velocity (v sin i )± 5[ 4] Age ± 5.8[ 8] Myr Other designations π2 Cyg ,81 Cyg ,BD +48°3504FK5 821HD 207330HIP 107533HR 8335SAO 51293[ 12] Database references SIMBAD data
Pi2 Cygni ,Latinized from π2 Cygni, is a possibletriple star [ 13] constellation ofCygnus . It is visible to thenaked eye about 2.5° east-northeast of theopen cluster M39 ,[ 14] apparent visual magnitude of 4.24.[ 2] parallax shift of 2.95 mas ,[ 1] light years from theSun .
Pi2 Cygni has been described as a single-lined[ 15] spectroscopic binary with anorbital period of 72.0162 days and aneccentricity of 0.34.[ 7] radial velocity variations on the timescale of the published orbit.[ 16] B-type giant star with astellar classification of B2.5 III.[ 3] Beta Cephei variable [ 4] [ 8] mass of the Sun and around 7.1[ 9] Sun's radius . The star is roughly 33[ 8] projected rotational velocity of 50[ 4] [ 10] solar luminosity from itsouter atmosphere at aneffective temperature of around 20,815[ 11]
The third member of this system is a magnitude 5.98 star at anangular separation of 0.10 arc seconds along aposition angle of 129°, as of 1996.[ 17]
InChinese ,螣蛇 Téng Shé Flying Serpent 2 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 andι Andromedae . Consequently, theChinese name for π2 Cygni itself is螣蛇三 Téng Shé sān the Third Star of Flying Serpent ).[ 18]
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