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16 Cygni

Related subjects: Space (Astronomy)

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16 Cygni A/B
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
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.


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 and 46.70 milliarcseconds for 16 Cygni B. 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.

System components

16 Cygni is a hierarchial triple system. Stars A and C form a close binary with a projected separation of 73 AU. 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.

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. 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.

16 Cyg A 16 Cyg B 16 Cyg C
Spectral type G1.5Vb G2.5Vb M?
B-V colour index 0.64 0.66  ?
U-B colour index 0.19 0.20  ?
Variable type none none  ?
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  ?

Planetary system

In 1996 an extrasolar planet in an eccentric orbit was announced around the star 16 Cygni B. The planet's orbit takes 798.5 days to complete, with a semimajor axis of 1.68 AU. 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
(in order from star)
Mass Semimajor axis
( AU)
Orbital period
Eccentricity Radius
Bb >1.68 ± 0.15  MJ

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.

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