Tau Cygni

{{short description|Variable star in the constellation Cygnus}}{{confuse|T Cygni}}

{{Starbox begin

| name=τ Cygni

}}

{{Starbox image

| image=

{{Location mark

|image=Cygnus constellation map.svg|alt=|float=center|width=280

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=τ Cygni

|x=164|y=443

}}

|caption=Location of τ Cygni (circled)

}}

{{Starbox observe

| epoch=J2000.0

| constell=Cygnus

| ra={{RA|21|14|47.4916}}

| dec={{DEC|+38|02|43.141}}

| appmag_v=3.65 - 3.75 {{nowrap|(3.80 / 6.69)}}

}}

{{Starbox character

| class=F2 IV + G0 V

| b-v=+0.38 / +0.60

| u-b=+0.03 / +0.09

| variable = δ Sct

}}

{{Starbox astrometry

| radial_v=−21.1

| prop_mo_ra=195.75

| prop_mo_dec=410.03

| parallax=47.80

| p_error=0.61

| absmag = 2.21 / 5.00

}}

{{Starbox orbit

| reference = {{cite web|title= Sixth Catalog of Orbits of Visual Binary Stars|url= https://crf.usno.navy.mil/usnodocspath?file_name=Orbital%20Elements%3A%20Text&source_file=/data_products/WDS/orb6/orb6orbits.txt}}

| period_unitless = 49.5240 years

| axis_unitless = 0.92224 arcseconds

| eccentricity = 0.24535

| inclination = 133.242 degrees

| node = 161.343 degrees

| periarg = 116.416 degrees

| periastron = 1938.5919

}}

{{Starbox detail

| component1 = τ Cyg A

| mass = 1.65

| radius = 2.48

| gravity = 3.87

| luminosity =

| temperature = 6,600

| metal_fe = 0.05

| rotational_velocity =

| age =

| component2 = τ Cyg B

| mass2 = 1.03

| radius2 = 0.93

| gravity2 = 4.52

| temperature2 = 5,670

}}

{{Starbox catalog

| names=τ Cygni, 65 Cygni, BD+37°4240, HD 202444, HIP 104887, HR 8130, SAO 71121, GC 29723, CCDM J21148+3803AB

}}

{{Starbox reference

| Simbad = tau+Cygni

| Simbad2 = tau+Cygni+A |sn2=A

| Simbad3 = tau+Cygni+B |sn3=B

}}

{{Starbox end}}

Tau Cygni, Latinised from τ Cygni, is a binary star system in the constellation Cygnus, approximately 69 light years away from Earth. This visual binary system has a period of 49.6 years.

The main star, 4th magnitude GJ 822.1 A, is a yellowish white subgiant star of the spectral type F2IV. It therefore has a surface temperature of 6,000 to 7,500 kelvins and is larger, hotter, and several times as bright as the Sun. Its companion, 6th magnitude GJ 822.1 B, is a yellow main sequence star of the spectral type G0V. It is similar to the Sun in size, surface temperature, and luminosity.

File:TauCygLightCurve.png for Tau Cygni plotted from TESS data]]

Tau Cygni is classified as a δ Scuti variable. The magnitude range is given as 3.65 to 3.75, which is the combined magnitude for both components, although the variable component is A.