Star · B9I
σ Cyg
σ Cyg is a supergiant star of spectral type B9I in the constellation Cygnus, 2,785 light-years from the Sun.
| Other names | HIP 105102 |
|---|---|
| Constellation | Cygnus |
| Distance | 2,785 light-years (853.9 pc) |
| Apparent magnitude | magnitude 4.22 |
| Absolute magnitude | magnitude −5.44 |
| Spectral type | B9I |
| Surface temperature | 9,050 K |
| Luminosity | 15,300 L☉ |
| Radius | 50.4 R☉ |
| Mass | 14.3 M☉ (estimated) |
| Right ascension (J2000) | 21h 17m 25.0s |
| Declination (J2000) | +39° 23′ 41″ |
| Space velocity (relative to the Sun) | 15.9 km/s |
In the sky
Visible to the naked eye under a dark sky (apparent magnitude 4.22). Visible from the whole Northern Hemisphere and south to latitude 51° S. North of latitude 51° N it never sets. It stands highest at midnight in August, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out around 760 BC. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 49 million years.
The Sun seen from there
From a planet around σ Cyg, the Sun would look like a star of magnitude 14.49, in the direction where our sky has the constellation Vela. It would be invisible to the naked eye.
Position, brightness and colour from the HYG / AT-HYG catalogue; temperature, luminosity, radius and mass are approximate values computed from these observations.