pi2 Cygni

{{short description|Triple star system in the constellation Cygnus}}

{{other stars by Bayer designation|Pi Cygni{{!}}π Cygni}}

{{Starbox begin

| name = Pi² Cygni

}}

{{Starbox observe

| epoch = J2000.0

| equinox = J2000.0 (ICRS)

| constell = Cygnus

| ra = {{RA|21|46|47.60832}}

| dec = {{DEC|+49|18|34.4511}}

| appmag_v = 4.24

}}

{{Starbox character

| class = B2.5 III

| b-v = −0.125

| u-b = −0.79

| r-i =

| variable = β Cep

}}

{{Starbox astrometry

| radial_v = −12.3

| prop_mo_ra = +2.77

| prop_mo_dec = −2.00

| parallax = 2.95

| p_error = 0.34

| parallax_footnote =

| absmag_v = −3.39

}}

{{Starbox orbit

| reference =

| period_unitless = 72.0162 d

| eccentricity = 0.34

| periastron = 2428410.6 JD

| periarg = 238.1

| k1 =7.8

}}

{{Starbox detail

| source =

| component1 = π² Cyg A

| mass = {{Val|8.4|0.4}}

| radius = 7.1

| luminosity_bolometric = 8,442

| temperature = {{Val|20815|1057|fmt=commas}}

| gravity = {{Val|3.69|0.16}}

| metal_fe = {{Val|0.04|0.09}}

| rotational_velocity = {{Val|50|5}}

| age_myr = {{Val|33.2|5.8}}

}}

{{Starbox catalog

| names = π² Cyg, 81 Cygni, BD+48°3504, FK5 821, HD 207330, HIP 107533, HR 8335, SAO 51293.

}}

{{Starbox reference

|Simbad=pi02+Cyg

}}

Pi² Cygni, Latinized from π² Cygni, is a triple star system in the northern constellation of Cygnus. It is visible to the naked eye about 2.5° east-northeast of the open cluster M39, having an apparent visual magnitude of 4.24. Based upon an annual parallax shift of 2.95 mas, it is located at a distance of roughly 1,100 light years from the Sun.

The inner pair of stars in this system form a single-lined spectroscopic binary with an orbital period of 72.0162 days and an eccentricity of 0.34. The primary, component A, is a B-type giant star with a stellar classification of B2.5 III. It is a Beta Cephei variable with an estimated 8.4 times the mass of the Sun and around 7.1 times the Sun's radius. The star is roughly 33 million years old and is spinning with a projected rotational velocity of 50 km/s. It is radiating 8,442 times the solar luminosity from its outer atmosphere at an effective temperature of around 20,815 K.

The third member of this system is a magnitude 5.98 star at an angular separation of 0.10 arc seconds along a position angle of 129°, as of 1996.

Historical names

In Chinese, {{lang|zh|螣蛇}} ({{lang|zh-Latn|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, the Chinese name for π² Cygni itself is {{lang|zh|螣蛇三}} ({{lang|zh-Latn|Téng Shé sān}}, {{langx|en|the Third Star of Flying Serpent}})

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