61 Cygni A
Star
61 Cygni A — the brighter of a wide pair of orange dwarfs (K5V) 11.4 light-years away in Cygnus. About 70% of the Sun's mass, it is a chromospherically active star. The pair is historic: in 1838 it became the first star to have its distance measured by parallax.
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Key facts
Mutual orbit
678 Earth years
247,640 Earth days
Mass
1.39 × 10³⁰ kg
0.7 M☉
Radius
462,640 km
66% of the Sun's radius
Surface temperature
4,374 K (4,101 °C)
Luminosity
5.86 × 10²⁵ W
Spectral type
K5V (orange dwarf)
Science
Physical
- Mass
- 1.39 × 10³⁰ kg · 0.7 M☉
- Radius
- 462,640 km · 66% of the Sun's radius
- Density
- 3,357 kg/m³ · 3.4× water
- Computed from mass and radius
- Spectral type
- K5V (orange dwarf)
Motion through space
- Note
- The motion of the pair's common centre of mass, computed as the mass-weighted mean of its stars' catalogued motions.
- Proper motion
- 5.23 arcseconds per year · its drift across our sky
- SIMBAD — 2020yCat.1350....0G
- Radial velocity
- -65.1 km/s · approaching the Sun
- SIMBAD — 2020yCat.1350....0G
- Speed across our line of sight
- 86.7 km/s
- Computed from proper motion and parallax
- Speed through space, relative to the Sun
- 108 km/s
- Computed from proper motion, parallax and radial velocity
Orbit (around the system barycenter)
- Semi-major axis
- 40.3 AU
- From the visual-binary orbit (P ≈ 678 yr, a ≈ 85 AU, e ≈ 0.48)
- Eccentricity
- 0.48
- From the visual-binary orbit (P ≈ 678 yr, a ≈ 85 AU, e ≈ 0.48)
- Orbital period
- 678.00 years
- From the visual-binary orbit (P ≈ 678 yr, a ≈ 85 AU, e ≈ 0.48)
Rotation
- Note
- Rotates about once every 35 days.
Composition
- By mass
- An orange main-sequence star about 70% of the Sun's mass and a sixth of its luminosity. It is chromospherically active, with starspots and a magnetic cycle (a BY Draconis-type variable).
Temperature
- Surface
- 4,374 K (4,101 °C)
Radiation & temperature
- Luminosity
- 5.86 × 10²⁵ W · 0.153 L☉
- Surface temperature
- 4,374 K (4,101 °C)
- Peak wavelength
- 662 nm · red light
- Computed (Wien's law) from the surface temperature
Discovery & history
- Method
- Naked-eye star
- Name
- '61 Cygni' is a Flamsteed number in Cygnus, the Swan. The pair is nicknamed 'Bessel's Star' and the 'Flying Star' for its role in history and its motion.
Noted by Giuseppe Piazzi in 1804 for its large proper motion — the 'Flying Star'. In 1838 Friedrich Bessel used that motion to select 61 Cygni for a parallax measurement, and succeeded: the FIRST reliable distance to any star beyond the Sun, opening the true scale of the cosmos.
Images
Images from open archives · credit shown per image