| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20 47 24.53766 |
| Declination | 36° 29′ 26.5737″ |
| Apparent magnitude (V) | 4.54 |
| Characteristics | |
| Spectral type | B5Ve |
| U−B color index | -0.50 |
| B−V color index | -0.11 |
| Variable type | Be star |
| Astrometry | |
| Radial velocity (Rv) | -23.20 km/s |
| Proper motion (μ) | RA: +14.71 mas/yr Dec.: -8.96 mas/yr |
| Parallax (π) | 4.24 ± 0.43 mas |
| Distance | approx. 770 ly (approx. 240 pc) |
| Details | |
| λ Cyg Aa | |
| Mass | 6.40 M☉ |
| Radius | 3.56 R☉ |
| Surface gravity (log g) | 3.195 cgs |
| Temperature | 13,925 K |
| Rotational velocity (v sin i) | 133 km/s |
| λ Cyg Ab | |
| Mass | 6.40 M☉ |
| λ Cyg B | |
| Mass | 5.12 M☉ |
| Other designations | |
| 54 Cygni, CCDM J20475+3629, GC 28994, HIP 102589, HR 7963, HD 198183, SAO 70505, WDS J20474+3629 | |
| Database references | |
| SIMBAD | data |
Lambda Cygni (λ Cyg) is a class B5V (blue main-sequence) star in the constellation Cygnus. Its apparent magnitude is 4.54 and it is approximately 770 light years away based on parallax.
Lambda Cygni is a multiple star, with components A, B, and C observed in the 19th century; the main component, A, is a spectroscopic binary itself with two components Aa and Ab reported at magnitudes 5.4 and 5.8 orbiting with a period of 12 years. Component B has type B7V, magnitude 6.26, and separation 0.77" (about 180 AU based on parallax). Component C has reported type K2III-IV, apparent magnitude 9.65, and separation about 85". Recent observations indicate the presence of additional smaller companions D (about 50" from A), E (about 8" from C), and F (about 40" from C) all around apparent magnitude 14.
References
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