Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Cygnus |
Right ascension | 20h 33m 54.18809s[2] |
Declination | +35° 15′ 03.0390″[2] |
Apparent magnitude (V) | 4.61[3] (4.84 + 7.30)[4] |
Characteristics | |
Spectral type | K6: Ib + B2.5:[3] |
B−V color index | 1.593±0.023[5] |
Variable type | Lc[6] |
Astrometry | |
Radial velocity (Rv) | −4.6±0.3[7] km/s |
Proper motion (μ) | RA: −6.12 mas/yr[2] Dec.: −4.166 mas/yr[2] |
Parallax (π) | 0.8792 ± 0.196 mas[2] |
Distance | 4072+965 −773 ly (1249+296 −237 pc)[8] |
Absolute magnitude (MV) | −4.1 (−4 + −1.5)[3] |
Orbit[9] | |
Period (P) | 1117±11 d |
Eccentricity (e) | 0.00 (assumed) |
Periastron epoch (T) | 2,447,088±10 JD |
Semi-amplitude (K1) (primary) | 2.0±0.1 km/s |
Details | |
47 Cyg Aa | |
Mass | 12.1±0.2[10] 19.4±3.9[11] M☉ |
Radius | 601[12] R☉ |
Surface gravity (log g) | 1.23[13] cgs |
Temperature | 4,217[13] K |
Metallicity [Fe/H] | 0.13[13] dex |
Age | 17.6±0.6[10] Myr |
47 Cyg Ab | |
Mass | 0.57[14] M☉ |
47 Cyg B | |
Mass | 10.96[14] M☉ |
Other designations | |
Database references | |
SIMBAD | data |
47 Cygni is a triple star[4][16] system in the northern constellation of Cygnus, and is located around 4,000 light years from the Earth. It is visible to the naked eye with a combined apparent visual magnitude of 4.61.[3] The system is moving closer to the Earth with a heliocentric radial velocity of −4.6 km/s.[7]
The dual nature of this system was recognized by Annie Cannon in 1912, and she assigned the pair separate Henry Draper Catalogue identifiers.[9] They orbit each other with a period of around 143.69 yr.[14] The primary component is itself a spectroscopic binary in a near circular orbit with a period of around 3.06 yr. The a sin i value for the primary is 30.8 ± 1.6 Gm (0.206 ± 0.011 AU), where a is the semimajor axis and i is the orbital inclination. It has been repeatedly resolved by speckle interferometery since 1973. Radio emission was detected from this system in 1985/86.[9]
The supergiant primary is a slow irregular variable with an amplitude of about 0.1 magnitudes.[6] Its angular diameter has been measured at 4.472±0.017 milliarcseconds using interferometry by the Navy Precision Optical Interferometer.[17] At the distance of 1,249 parsecs,[8] it yield a radius of 601 R☉.[12] Its close companion has 57% of the mass of the Sun.[14] The secondary is a hot B-type main-sequence star, but still 2.5 magnitudes fainter than the primary.[4]
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