16 Cygni
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| Observation data Epoch J2000.0 |
|
|---|---|
| Constellation | Cygnus |
| 16 Cygni A | |
| Right ascension | 19h 41m 48.9535s |
| Declination | +50° 31′ 30.217″ |
| Apparent magnitude (V) | 5.96 |
| 16 Cygni B | |
| Right ascension | 19h 41m 51.9720s |
| Declination | +50° 31′ 03.083″ |
| Apparent magnitude (V) | 6.20 |
| Astrometry | |
| Radial velocity (Rv) | -25.6 km/s |
| Proper motion (μ) | RA: -147.75 mas/yr Dec.: -158.85 mas/yr |
| Parallax (π) | 46.25 ± 0.50 mas |
| Distance | 70.5 ly (21.6 pc) |
| Absolute magnitude (MV) | 4.29 / 4.53 |
| Other designations | |
16 Cygni (abbreviated 16 Cyg) is a triple star system located around 70 light-years away in the constellation Cygnus. It consists of two Sun-like yellow dwarf stars and a red dwarf. In 1996 an extrasolar planet was discovered in an eccentric orbit around the sunlike star 16 Cygni B.
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[edit] Distance
The parallax of the two brightest stars were measured as part of the Hipparcos astrometry mission. This yielded a parallax of 46.25 milliarcseconds for 16 Cygni A[1] and 46.70 milliarcseconds for 16 Cygni B.[2] Since the two components are associated, it is reasonable to assume they lie at the same distance, so the different parallaxes are a result of experimental error (indeed, when the associated parallax errors are taken into account, the ranges of the parallaxes overlap). Using the parallax of the A component, the distance is 21.6 parsecs. The parallax of the B component corresponds to a distance of 21.4 parsecs.
[edit] System components
16 Cygni is a hierarchial triple system. Stars A and C form a close binary with a projected separation of 73 AU.[3] The orbital elements of the A-C binary are currently unknown. At a distance of 860 AU from A is a third component designated 16 Cygni B. The orbit of B relative to the A-C pair is not well determined: plausible orbits range in period from 18,200 to 1.3 million years, with a semimajor axis ranging from 877 to 15,180 AU.[4]
Both 16 Cygni A and 16 Cygni B are yellow dwarf stars like our Sun. According to data from the Geneva-Copenhagen survey, both stars have masses similar to the sun.[5][6] Age estimates for the two stars vary slightly, but 16 Cygni is likely to be much older than our solar system, at around 10,000 million years old. 16 Cygni C is much fainter than either of these stars, and may be a red dwarf.[3]
| 16 Cyg A | 16 Cyg B | 16 Cyg C | |
|---|---|---|---|
| Characteristics | |||
| Spectral type | G1.5Vb | G2.5Vb | M? |
| B-V color index | 0.64 | 0.66 | ? |
| U-B color index | 0.19 | 0.20 | ? |
| Variable type | none | none | ? |
| Details | |||
| Mass (M☉) | 1.02 | 0.97 | ? |
| Radius (R☉) | 1.4 | 1.2 | ? |
| Luminosity (L☉) | 1.6 | 1.3 | ? |
| Temperature (K) | 5825 | 5640 | ? |
| Metallicity | 114% | 123% | ? |
| Rotation (days) | 26.9 | 29.1 | ? |
| Age (years) | 10.4 × 109 | 9.9 × 109 | ? |
[edit] Planetary system
In 1996 an extrasolar planet in an eccentric orbit was announced around the star 16 Cygni B.[7] The planet's orbit takes 798.5 days to complete, with a semimajor axis of 1.68 AU.[8] Like the majority of known extrasolar planets, 16 Cygni Bb was detected by measuring the radial velocity of its parent star, which only gives a lower limit on the mass: in this case, about 1.68 times that of Jupiter.
| Companion (In order from star) |
Mass (MJ) |
Orbital period (days) |
Semimajor axis (AU) |
Eccentricity |
|---|---|---|---|---|
| Bb | >1.68 ± 0.15 | 798.5 ± 1.0 | 1.681 ± 0.097 | 0.681 ± 0.017 |
[edit] References
- ^ HIP 96895. The Hipparcos and Tycho Catalogues. ESA (1997). Retrieved on 27 June, 2006.
- ^ HIP 96901. The Hipparcos and Tycho Catalogues. ESA (1997). Retrieved on 27 June, 2006.
- ^ a b Raghavan, D. et al. (2006) "Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems" (preprint)
- ^ Hauser, H., Marcy, G. (1999). "The Orbit of 16 Cygni AB". Publications of the Astronomical Society of the Pacific 111: 321 – 334.
- ^ Nordstrom et al. (2004). Record 13627. Geneva-Copenhagen Survey of Solar neighbourhood. Retrieved on 4 July, 2006.
- ^ Nordstrom et al. (2004). Record 13631. Geneva-Copenhagen Survey of Solar neighbourhood. Retrieved on 4 July, 2006.
- ^ Cochran et al. (1997). "The Discovery of a Planetary Companion to 16 Cygni B". The Astrophysical Journal 483: 457-463.
- ^ Butler, R. et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal 646: 505 – 522. (web version)
[edit] External links
- SIMBAD: 16 Cyg A
- SIMBAD: 16 Cyg B
- SIMBAD: 16 Cyg C
- Extrasolar Planets Encyclopaedia: 16 Cyg Bb
- Extrasolar Visions: 16 Cygni B
- Extrasolar Visions: 16 Cygni Bb
- 16 Cygni-B by Professor Jim Kaler.
- 16 Cygni 2? at SolStation.
