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16 Cygni

2007 Schools Wikipedia Selection. Related subjects: Space (Astronomy)

   CAPTION: 16 Cygni A/B

                             Observation data
   Epoch J2000.0
   Constellation             Cygnus
   16 Cygni A
   Right ascension           19^h 41^m 48.9535^s
   Declination               +50° 31′ 30.217″
   Apparent magnitude (V)    5.96
   16 Cygni B
   Right ascension           19^h 41^m 51.9720^s
   Declination               +50° 31′ 03.083″
   Apparent magnitude (V)    6.20
                                Astrometry
   Radial velocity (R[v])    -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 (M[V]) 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.

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 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
                              Characteristics
               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        ?
                                  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 × 10^9 9.9 × 10^9     ?

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.

        Companion
   (In order from star)     Mass
                          ( M[J])    Orbital period
                                         (days)    Semimajor axis
                                                       ( AU)     Eccentricity
            Bb          >1.68 ± 0.15  798.5 ± 1.0  1.681 ± 0.097 0.681 ± 0.017

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