CG Cygni
Eclipsing ternary star system in constellation Cygnus
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CG Cygni is a ternary star system composed of main-sequence stars in the constellation of Cygnus about 320 light years away.
Right ascension20h 58m 13.4534s[2]
Declination+35° 10′ 29.6642″[2]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h 58m 13.4534s[2] |
| Declination | +35° 10′ 29.6642″[2] |
| Characteristics | |
| BD+34 4217A | |
| Evolutionary stage | main-sequence star[3] |
| Spectral type | G9+K3[3] |
| Apparent magnitude (g) | 10.06[4] |
| Variable type | RS Canum Venaticorum variable |
| BD+34 4217B | |
| Apparent magnitude (g) | 11.74[5] |
| Astrometry | |
| BD+34 4217A | |
| Proper motion (μ) | RA: 6.638±0.014 mas/yr[4] Dec.: −13.87±0.02 mas/yr[4] |
| Parallax (π) | 10.2393±0.0170 mas[4] |
| Distance | 318.5 ± 0.5 ly (97.7 ± 0.2 pc) |
| BD+34 4217B | |
| Proper motion (μ) | RA: 9.86±0.05 mas/yr[5] Dec.: -16.32±0.06 mas/yr[5] |
| Parallax (π) | 10.2046±0.0391 mas[5] |
| Distance | 320 ± 1 ly (98.0 ± 0.4 pc) |
| Orbit | |
| Primary | BD+34 4217Aa |
| Name | BD+34 4217Ab |
| Period (P) | 0.6311 d[6] |
| Inclination (i) | 82.602±0.099[7]° |
| Details | |
| BD+34 4217Aa | |
| Mass | 0.97[7] M☉ |
| Radius | 0.893[8] R☉ |
| Temperature | 5200[3] K |
| BD+34 4217Ab | |
| Mass | 0.80[7] M☉ |
| Radius | 0.838[8] R☉ |
| Temperature | 4400[3] K |
| Other designations | |
| 2MASS J20581343+3510298, HIP 103505, GSC 02696-02945, BD+34 4217, Gaia DR2 1866704219781935360 | |
| BD+34 4217A: CG Cyg A, TYC 2696-2945-1, Gaia EDR3 1866704219781935360 | |
| BD+34 4217B: CG Cyg B, TYC 2696-2945-2, Gaia EDR3 1866704219775706624 | |
| Database references | |
| SIMBAD | data |
System
The star CG Cygni A (BD+34 4217A) itself is a close binary system with ongoing mass transfer between components. The orbital period of the binary is currently increasing. An additional third body (either star or planet) was suspected to exist in the system with an orbital period of 15.9-51 years, creating cyclic period variations of the binary.[6] It was finally confirmed as the star CG Cygni B (BD+34 4217B) in 2020, at a 1.16 arcsecond separation from the primary.[9]