|
61 Cygni is a star in the constellation Cygnus. 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. This large proper motion, the largest known for any star at the time, 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. Only a few years later, however, Groombridge 1830 was discovered to have a larger proper motion. 61 Cygni retains the distinction of having the largest proper motion of any star visible with the naked eye (although Groombridge 1830 at magnitude 6.4 can be seen with the naked eye under exceptionally dark skies). 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. 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 star 61 Cygni A is of apparent magnitude 5.2, the fainter 61 Cygni B is 6.1. The two orbit their common barycenter in a period of 653.2 years, with a mean separation of about 84 AU. 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 Bs planet 61 Cygni B has been claimed to have a planet or brown dwarf companion, but the claim has not been confirmed. See also | ||||||||
|
| |||||||||
 |
|
| |