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16 Cygni
Observation data
Epoch J2000.0      Equinox 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
Characteristics
Spectral type G1.5Vb / G2.5Vb / M?V
U-B color index 0.19 / 0.20
B-V color index 0.64 / 0.66
Variable type None
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
Details
Mass 1.02 / 0.97 M☉
Radius 1.4 / 1.2 R☉
Luminosity 1.6 / 1.3 L☉
Temperature 5825 / 5640 K
Metallicity 114% / 123% Sun
Rotation 26.9 / 29.1
Age 10.4×109 / 9.9×109 years
Other designations
Database references
SIMBAD data
Database references
SIMBAD data

16 Cygni is a triple star system approximately 70 light-years away in the constellation of 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.

Contents

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 A1 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.

Stellar 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 was determined in 1999 and not updated since (as of June 2007): plausible orbits range in period from 18,200 to 1.3 million years, with a semimajor axis ranging from 877 to 15,180 AU. In addition B orbits between 100 and 160 degrees inclination, that is against the A-C pole such that 90 degrees would be ecliptical.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.56 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

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.

There was a METI message sent to the 16 Cygni system. It was transmitted from Eurasia's largest radar — 70-meter Eupatoria Planetary Radar. The message was named Cosmic Call 1, it was sent on May 24, 1999, and it will arrive at 16 Cygni in November 2069.9

"For the 16 Cyg B system, only particles inside of about 0.3 AU remained stable [within a million years of formation], leaving open the possibility of short-period planets". For them, observation rules out any such planet of over a Neptune mass.10


The 16 Cygni B system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity
b >1.68 ± 0.15 MJ 1.681 ± 0.097 798.5 ± 1.0 0.681 ± 0.017

See also

References

  1. ^ "HIP 96895". The Hipparcos and Tycho Catalogues. ESA (1997). Retrieved on 27 June, 2006.
  2. ^ "HIP 96901". The Hipparcos and Tycho Catalogues. ESA (1997). Retrieved on 27 June, 2006.
  3. ^ a b Raghavan et al. (2006). "Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems". The Astrophysical Journal 646 (1): 523–542. http://www.journals.uchicago.edu/doi/full/10.1086/504823. 
  4. ^ Hauser, H., Marcy, G. (1999). "The Orbit of 16 Cygni AB". Publications of the Astronomical Society of the Pacific 111 (757): 321–334. doi:10.1086/316328. http://www.journals.uchicago.edu/doi/full/10.1086/316328. 
  5. ^ Holmberg et al. (2007). "Record 13627". Geneva-Copenhagen Survey of Solar neighbourhood. Retrieved on 19 November, 2008.
  6. ^ Holmberg et al. (2007). "Record 13631". Geneva-Copenhagen Survey of Solar neighbourhood. Retrieved on 19 November, 2008.
  7. ^ Cochran et al. (1997). "The Discovery of a Planetary Companion to 16 Cygni B". The Astrophysical Journal 483 (1): 457–463. doi:10.1086/304245. http://www.journals.uchicago.edu/doi/full/10.1086/304245. 
  8. ^ Butler et al. (2006). "Catalog of Nearby Exoplanets" (abstract). The Astrophysical Journal 646 (1): 505–522. doi:10.1086/504701. http://www.journals.uchicago.edu/doi/abs/10.1086/504701.  (web version)
  9. ^ (Russian) http://www.cplire.ru/rus/ra&sr/VAK-2004.html
  10. ^ WITTENMYER R., ENDL M., COCHRAN W. & LEVISON H. (2007). "Dynamical and Observational Constraints on Additional Planets in Highly Eccentric Planetary Systems". Astronomical Journal 134: 1276. http://arxiv.org/abs/0706.1962v1. 

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