Lambda Cygni
Star in the constellation Cygnus
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Lambda Cygni (λ Cyg) is a class B5V (blue main-sequence) star in the constellation Cygnus. Its apparent magnitude is 4.54[2] and it is approximately 770 light years away based on parallax.[1]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h 47m 24.53766s[1] |
| Declination | +36° 29′ 26.5737″[1] |
| Apparent magnitude (V) | 4.54[2] |
| Characteristics | |
| Spectral type | B5Ve[3] |
| U−B color index | −0.50 [2] |
| B−V color index | −0.11 [2] |
| Variable type | Be star[4] |
| Astrometry | |
| Radial velocity (Rv) | -23.20[5] km/s |
| Proper motion (μ) | RA: +14.71[1] mas/yr Dec.: −8.96[1] mas/yr |
| Parallax (π) | 4.24±0.43 mas[1] |
| Distance | approx. 770 ly (approx. 240 pc) |
| Details | |
| λ Cyg Aa | |
| Mass | 6.40[6] M☉ |
| Radius | 3.56[7] R☉ |
| Surface gravity (log g) | 3.195[8] cgs |
| Temperature | 13,925[8] K |
| Rotational velocity (v sin i) | 133[8] km/s |
| λ Cyg Ab | |
| Mass | 6.40[6] M☉ |
| λ Cyg B | |
| Mass | 5.12[6] 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 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.[9] Component B has type B7V, magnitude 6.26, and separation 0.77" (about 180 AU based on parallax).[9][10] Component C has reported type K2III-IV, apparent magnitude 9.65, and separation about 85".[11] 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.[11]