σ Cygni (sigma Cygni)

σ Cygni is a variable supergiant star in the constellation of Cygnus.

σ Cygni visual magnitude is 4.23. Because of its moderate brightness, σ 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 σ Cygni:

Color of σ Cygni ⬤

Magnitude of σ Cygni 4.23

Class Supergiant

VISIBILITY RIGHT NOW σ Cygni (sigma Cygni) is above the horizon from Greenwich, United Kingdom [change]. Altitude: 10°.

Celestial coordinates and finder chart of σ Cygni

σ 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 σ Cygni are provided in the following table:

Right Ascension J2000 21h 17m 25s

Declination J2000 +39° 23’ 40”

Galactic Longitude 84.19°

Galactic Latitude -6.87°

Constellation Cygnus

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

Simplified finder chart for σ Cygni (sigma Cygni).

Visibility of σ Cygni from your location

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

σ Cygni (sigma Cygni) is circumpolar and transits at 08:47 UTC (altitude: 77.9°)

Digitized Sky Survey image of σ Cygni

The image below is a photograph of σ 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 σ Cygni is 0.001 arcsec per year in Right Ascension and -0.003 arcsec per year in Declination and the associated displacement for the next 100000 years is represented with the red arrow.

DSS2 image of σ Cygni. The red arrow shows the motion of σ Cygni during the next 100000 years (1.67 arcmin in Right Ascension and -5.00 arcmin in declination);

Distance of σ Cygni from the Sun and relative movement

σ Cygni is distant 4,527.78 light years from the Sun and it is moving towards the Sun at the speed of 4 kilometers per second.

Distance (parsec) 1,388.89 pc

Distance (light year) 4,527.78 ly

Heliocentric radial velocity -4 km/s

Proper Motion RA 0.001 arcsec/year

Proper Motion Dec -0.003 arcsec/year

Spectral properties of σ Cygni

σ Cygni belongs to spectral class B9 and has a luminosity class of I corresponding to a supergiant star.

Absolute magnitude -6.48

Spectral Type B9I

Color Index (B-V) 0.12

Temperature of σ Cygni 8839K

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

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

Alternative designations of σ Cygni

Bayer designation σ Cygni
(sigma Cygni)

Flamsteed designation 67 Cygni

Henry Draper Catalogue HD202850

SAO Catalogue SAO71165

Hipparcos Catalogue HIP105102

Durchmusterung Catalogue BD+38 4431

FK5 Catalogue 1558

General Catalogue of Variable Stars 13640

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In Evidence

Other stars in Cygnus