61 Cygni
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cygnus |
| 61 Cygni A | |
| Right ascension | 21h 06m 53.9396s[1] |
| Declination | +38° 44′ 57.902″[1] |
| Apparent magnitude (V) | 5.21[2] |
| 61 Cygni B | |
| Right ascension | 21h 06m 55.2638s[3] |
| Declination | +38° 44′ 31.359″[3] |
| Apparent magnitude (V) | 6.05[4] |
| Characteristics | |
| 61 Cyg A | |
| Evolutionary stage | main sequence[1] |
| Spectral type | K5V[2] |
| U−B color index | +1.155[5] |
| B−V color index | +1.139[5] |
| Variable type | BY Dra[6] |
| 61 Cyg B | |
| Evolutionary stage | main sequence[3] |
| Spectral type | K7V |
| U−B color index | +1.242[5] |
| B−V color index | +1.320[5] |
| Variable type | Flare star[7] |
| Astrometry | |
| 61 Cygni A | |
| Radial velocity (Rv) | −65.97±0.12[1] km/s |
| Proper motion (μ) | RA: 4,164.209 mas/yr[1] Dec.: 3,249.614 mas/yr[1] |
| Parallax (π) | 285.9949±0.0599 mas[1] |
| Distance | 11.404 ± 0.002 ly (3.4966 ± 0.0007 pc) |
| Absolute magnitude (MV) | 7.506[8] |
| 61 Cygni B | |
| Radial velocity (Rv) | −64.59±0.12[3] km/s |
| Proper motion (μ) | RA: 4,105.976 mas/yr[3] Dec.: 3,155.942 mas/yr[3] |
| Parallax (π) | 286.0054±0.0289 mas[3] |
| Distance | 11.404 ± 0.001 ly (3.4964 ± 0.0004 pc) |
| Absolute magnitude (MV) | 8.228[8] |
| Orbit[9] | |
| Period (P) | 707.1+4.5 −4.4 years |
| Semi-major axis (a) | 86.76+0.16 −0.15 au |
| Eccentricity (e) | 0.4424+0.0056 −0.0057 |
| Inclination (i) | 52.99±0.12° |
| Longitude of the node (Ω) | 355.73±0.30° |
| Periastron epoch (T) | JD = 2596496+1255 −1213 |
| Argument of periastron (ω) (secondary) | 150.61+0.68 −0.67° |
| Details | |
| 61 Cygni A | |
| Mass | 0.6771+0.0052 −0.0051[9] M☉ |
| Radius | 0.667±0.005[10] R☉ |
| Luminosity | 0.150±0.004[10] L☉ |
| Surface gravity (log g) | 4.63±0.01[10] cgs |
| Temperature | 4,398±34[10] K |
| Metallicity [Fe/H] | −0.13±0.03[10] dex |
| Rotation | 35.54±0.47[11] days |
| Age | 6.1±1.0[12] Gyr |
| 61 Cygni B | |
| Mass | 0.6289+0.0094 −0.0092[9] M☉ |
| Radius | 0.594±0.008[10] R☉ |
| Luminosity | 0.097±0.003[10] L☉ |
| Surface gravity (log g) | 4.68±0.02[10] cgs |
| Temperature | 4,174±47[10] K |
| Metallicity [Fe/H] | −0.21±0.07[10] dex |
| Rotation | 34.55±0.57[11] days |
| Age | 6.1±1.0[12] Gyr |
| Other designations | |
| GJ 820 A/B, Struve 2758, ADS 14636, V1803 Cygni, GCTP 5077.00[13] | |
| 61 Cygni A: V1803 Cygni, HD 201091, HIP 104214, HR 8085, BD+38°4343, LHS 62, SAO 70919[6] | |
| 61 Cygni B: HD 201092, HIP 104217, HR 8086, BD+38°4344, LHS 63[7] | |
| Database references | |
| SIMBAD | The system |
| A | |
| B | |
61 Cygni /ˈsɪɡni/ is a binary star system in the constellation Cygnus, consisting of a pair of K-type dwarf stars that orbit each other in a period of about 659 years. Of apparent magnitude 5.20 and 6.05, respectively, they can be seen with binoculars in city skies or with the naked eye in rural areas without light pollution.
61 Cygni first attracted the attention of astronomers when its large proper motion was first demonstrated by Giuseppe Piazzi in 1804. In 1838, Friedrich Bessel measured its distance from Earth at about 10.4 light-years, very close to the actual value of about 11.4 light-years; this was the first distance estimate for any star other than the Sun, and the first star to have its stellar parallax measured. Among all stars or stellar systems listed in the latest Gaia catalogues, 61 Cygni has the sixth-highest proper motion, and the highest among all naked-eye visible stars.[note 1][14]
Over the course of the twentieth century, several different astronomers reported evidence of a massive planet orbiting one of the two stars, but recent high-precision radial velocity observations have shown that all such claims were unfounded.[15] No planets have been confirmed in this stellar system to date.
- ^ a b c d e f Cite error: The named reference
GaiaDR3-awas invoked but never defined (see the help page). - ^ a b Cite error: The named reference
fischer-2019was invoked but never defined (see the help page). - ^ a b c d e f Cite error: The named reference
GaiaDR3-bwas invoked but never defined (see the help page). - ^ Cite error: The named reference
the internet stellar database-2011was invoked but never defined (see the help page). - ^ a b c d Cite error: The named reference
catalano s-1979was invoked but never defined (see the help page). - ^ a b Cite error: The named reference
SIMBAD Query - 61 Cygni Awas invoked but never defined (see the help page). - ^ a b Cite error: The named reference
SIMBAD Query - 61 Cygni Bwas invoked but never defined (see the help page). - ^ a b Cite error: The named reference
kovtyukh-2003was invoked but never defined (see the help page). - ^ a b c Cite error: The named reference
NEID2025was invoked but never defined (see the help page). - ^ a b c d e f g h i j Cite error: The named reference
Soubiran2024was invoked but never defined (see the help page). - ^ a b Cite error: The named reference
olspert-2018was invoked but never defined (see the help page). - ^ a b Cite error: The named reference
kervella-2008was invoked but never defined (see the help page). - ^ Cite error: The named reference
SIMBAD Query - 61 Cygniwas invoked but never defined (see the help page). - ^ Cite error: The named reference
Gaia-IoW_20250513was invoked but never defined (see the help page). - ^ Cite error: The named reference
Wittenmyer2006was invoked but never defined (see the help page).
Cite error: There are <ref group=note> tags on this page, but the references will not show without a {{reflist|group=note}} template (see the help page).