61 Cygni is a star in the Cygnus constellation. Though it is among the least conspicuous of stars visible in the night sky to an observer without an optical instrument, 61 Cygni attracted the attention of astronomers due to its large proper motion. The star is in fact a double star system.

This system should not be confused with 16 Cygni, which includes a Sun-like star with a very eccentric planet.

General information

61 Cygni's proper motion is so great, relatively speaking, that its apparent position shifts by an amount equal to the width of the full moon in a mere 150 years.

The large proper motion, greater than that of any other star visible with the naked eye, made 61 Cygni a candidate for the determination of its distance by the method of parallax when the quality of astronomical observations first made this possible. The star therefore has the distinction of being the first star (excluding the Sun) to have its distance determined. This was accomplished by Friedrich Wilhelm Bessel in 1838 who arrived at a figure close to the currently accepted value of 11.4 light years. Subsequent observations showed that, in addition to the closeness of the star, the high proper motion was attributable to its actual velocity relative to the Sun being large and almost transverse to our line of sight to the star.

From the point of the view of the casual astronomical observer, 61 Cygni is not particularly spectacular.

The binary system

Although it appears to be a single star to the naked eye, 61 Cygni is in fact a widely separated binary system, composed of two K class (orange) main sequence stars, 61 Cygni A and 61 Cygni B.

The brighter is of apparent magnitude 5.2, the fainter 6.1. The two orbit their common barycenter in a period of 653.2 years.

An observer using 7×50 binoculars can find 61 Cygni two binocular fields south-east of the bright star Deneb. An observer using larger binoculars, or a telescope, will be able to resolve the two components of the binary.

61 Cygni A

61 Cygni A is also known as HD 201091, HR 8085, BD+38°4343, GCTP 5077.00A and LHS 62.

• Parallax: 0.287 arcsecs
• Spectral type: K5 V
• Radial velocity: -65 km/s
• Proper Motion: 5.283 arcsecs/year
• Apparent Visual Magnitude: 5.20
• Absolute Visual Magnitude: 7.49
• Luminosity: 0.16 Solar Luminosities

61 Cygni B

61 Cygni B is also known as HD 201092, HR 8086, BD+38°4344, GCTP 5077.00B and LHS 63.

• Parallax: 0.285 arcsecs
• Spectral type: K7 V
• Radial velocity: -64 km/s
• Proper Motion: 5.172 arcsecs/year
• Apparent Visual Magnitude: 6.05
• Absolute Visual Magnitude: 8.33
• Luminosity: 0.095 solar luminosities

61 Cygni B's planet

61 Cygni B has been claimed to have a planet or brown dwarf companion, but the claim has not been confirmed.

61 Cygni in Fiction

• 61 Cygni (Star Trek) is held by many fans of Star Trek to be the home star system of the Tellarite race.
• 61 Cygni (Foundation universe) is one of Lord Dorwin's hypothetical originary planets of the human race in Isaac Asimov's Foundation Series.
• 61 Cygni (or 'Swan') is the sun of the planet Sky's Edge in Alastair Reynolds' Revelation Space universe.
• 61 Cygni A is the sun around which the planet Mesklin revolves in Hal Clement's series of short stories.
• In Clifford D. Simak's novel Time and Again, 61 Cygni is a mysterious stellar system whose planets are impossible to approach.

See also

• List of nearest stars

External links

• Jim Kaler's Stars: 61 Cygni
• Sol Station — 61 Cygni