Claims of A Planetary System
On several occasions, it has been claimed that 61 Cygni has unseen low-mass companions, planets or a brown dwarf. Kaj Strand of the Sproul Observatory, under the direction of Peter van de Kamp, made the first such claim in 1942 using observations to detect tiny but systematic variations in the orbital motions of 61 Cygni A and B. These perturbations suggested that a third body was orbiting 61 Cygni A. In 1957, he narrowed his uncertainties, claiming that the object had a mass eight times the mass of Jupiter, a calculated orbital period of 4.8 years, and a semi-major axis of 2.4 A.U. In 1977, Soviet astronomers at the Pulkovo Observatory near Saint Petersburg suggested that the system included three planets: two giant planets with six and twelve Jupiter masses around 61 Cyg A, and one giant planet with seven Jupiter masses around 61 Cygni B. In 1978, Wulff Dieter Heintz of the Sproul Observatory proved that these claims, as well as the claims for unseen companions around many other stars, were spurious, having failed to detect any evidence of such motion down to six percent of the Sun's mass—equivalent to about 60 times the mass of Jupiter.
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