τ Cygni (tau Cygni)

τ Cygni is a variable and multiple sub-giant star in the constellation of Cygnus.

τ Cygni visual magnitude is 3.72. Because of its moderate brightness, τ Cygni should be easily visible from locations with dark skyes, while it can be barely visible, or not visible at all, from skyes affected by light pollution.

The table below summarizes the key facts about τ Cygni:

Color of τ Cygni ⬤

Magnitude of τ Cygni 3.72

Class Sub-giant

VISIBILITY RIGHT NOW τ Cygni (tau Cygni) is above the horizon from Greenwich, United Kingdom [change]. Altitude: 1°.

Celestial coordinates and finder chart of τ Cygni

τ Cygni is situated north of the celestial equator, as such, it is more easily visible from the northern hemisphere. Celestial coordinates for the J2000 equinox as well as galactic coordinates of τ Cygni are provided in the following table:

Right Ascension J2000 21h 14m 47s

Declination J2000 +38° 02’ 44”

Galactic Longitude 82.85°

Galactic Latitude -7.43°

Constellation Cygnus

The simplified sky map below shows the position of τ Cygni in the sky:

Simplified finder chart for τ Cygni (tau Cygni).

Visibility of τ Cygni from your location

Location: Greenwich, United Kingdom [change]
Latitude: 51° 28’ 47” N
Longitude: 0° 00’ 00” E
Timezone: Europe/London

Today's τ Cygni (tau Cygni) rise, transit and set times from Greenwich, United Kingdom [change] are the following (all times relative to the local timezone Europe/London):

Azimuth: 52.0° RISE 21:58

Max altitude: 76.6° TRANSIT 9:16

Azimuth: 308.0° SET 20:30

RIGHT NOW τ Cygni (tau Cygni) is above the horizon from Greenwich, United Kingdom

Digitized Sky Survey image of τ Cygni

The image below is a photograph of τ Cygni from the Digitized Sky Survey 2 (DSS2 - see the credits section) taken in the red channel. The area of sky represented in the image is 0.5x0.5 degrees (30x30 arcmins). The proper motion of τ Cygni is 0.16 arcsec per year in Right Ascension and 0.435 arcsec per year in Declination and the associated displacement for the next 1000 years is represented with the red arrow.

DSS2 image of τ Cygni. The red arrow shows the motion of τ Cygni during the next 1000 years (2.67 arcmin in Right Ascension and 7.25 arcmin in declination);

Distance of τ Cygni from the Sun and relative movement

τ Cygni is distant 68.20 light years from the Sun and it is moving towards the Sun at the speed of 21 kilometers per second.

Distance (parsec) 20.92 pc

Distance (light year) 68.20 ly

Heliocentric radial velocity -21 km/s

Proper Motion RA 0.16 arcsec/year

Proper Motion Dec 0.435 arcsec/year

Spectral properties of τ Cygni

τ Cygni belongs to spectral class F2 and has a luminosity class of IV corresponding to a sub-giant star.

Absolute magnitude 2.12

Spectral Type F2IV

Color Index (B-V) 0.39

Temperature of τ Cygni 6934K

The red dot in the diagram below shows where τ Cygni is situated in the Hertzsprung–Russell diagram.

H-R diagram showing the position of τ Cygni. Attribution: Richard Powell / CC BY-SA

τ Cygni star system properties

τ Cygni is a visual double star which can be observed with the help of large telescopes. The table below shows key information about the τ Cygni double sysyem:

Main star magnitude 3.72

Secondary star magnitude 6.22

Magnitude difference 2.5

Separation 1 arcsec

Alternative designations of τ Cygni

Bayer designation τ Cygni
(tau Cygni)

Flamsteed designation 65 Cygni

Henry Draper Catalogue HD202444

SAO Catalogue SAO71121

Hipparcos Catalogue HIP104887

Durchmusterung Catalogue BD+37 4240

Gliese Catalogue Gl 822.1A

General Catalogue of Variable Stars Tau Cyg

Aitken Double Star Catalogue ADS14787

How to support us

In Evidence

Other stars in Cygnus