16 Cygni

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16 Cygni A/B
Observation data
Epoch J2000.0
Constellation
(pronunciation)		 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 A

Gl 765.1 A, HR 7503, BD +50°2847, HD 186408, LTT 15750, GCTP 4634.00, SAO 31898, Struve 4046A, HIP 96895

16 Cygni B

Gl 765.1 B, HR 7504, BD +50°2848, HD 186427, LTT 15751, SAO 31899, Struve 4046B, HIP 96901

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.

Contents

[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.

The 16 Cygni system
Planet
(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] METI message to 16 Cygni A

There was a METI message sent to 16 Cygni A. 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 A in November 2069.[9]

[edit] 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, D. et al. (2006) "Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems" (preprint)
  4. ^ Hauser, H., Marcy, G. (1999). "The Orbit of 16 Cygni AB" (abstract). Publications of the Astronomical Society of the Pacific 111: 321 – 334. doi:10.1086/316328. 
  5. ^ Nordstrom et al. (2004). Record 13627. Geneva-Copenhagen Survey of Solar neighbourhood. Retrieved on 4 July, 2006.
  6. ^ Nordstrom et al. (2004). Record 13631. Geneva-Copenhagen Survey of Solar neighbourhood. Retrieved on 4 July, 2006.
  7. ^ Cochran et al. (1997). "The Discovery of a Planetary Companion to 16 Cygni B" ([dead link]). The Astrophysical Journal 483: 457-463. doi:10.1086/304245. 
  8. ^ Butler, R. et al. (2006). "Catalog of Nearby Exoplanets" (abstract). The Astrophysical Journal 646: 505 – 522. doi:10.1086/504701.  (web version)
  9. ^ (Russian) http://www.cplire.ru/rus/ra&sr/VAK-2004.html

[edit] External links