• Source: 47 Cygni

47 Cygni is a triple star system in the northern constellation of Cygnus, and is located around 4,000 light years from the Earth. It is visible to the naked eye with a combined apparent visual magnitude of 4.61. The system is moving closer to the Earth with a heliocentric radial velocity of −4.6 km/s.
The dual nature of this system was recognized by Annie Cannon in 1912, and she assigned the pair separate Henry Draper Catalogue identifiers. They orbit each other with a period of around 143.69 yr. The primary component is itself a spectroscopic binary in a near circular orbit with a period of around 3.06 yr. The a sin i value for the primary is 30.8 ± 1.6 Gm (0.206 ± 0.011 AU), where a is the semimajor axis and i is the orbital inclination. It has been repeatedly resolved by speckle interferometery since 1973. Radio emission was detected from this system in 1985/86.
The supergiant primary is a slow irregular variable with an amplitude of about 0.1 magnitudes. Its angular diameter has been measured at 4.472±0.017 milliarcseconds using interferometry by the Navy Precision Optical Interferometer. At the distance of 1,249 parsecs, it yield a radius of 601 R☉. Its close companion has 57% of the mass of the Sun. The secondary is a hot B-type main-sequence star, but still 2.5 magnitudes fainter than the primary.




References

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