High precision radial velocity observations of the solar-type star 16 Cygni B ( HR 7504 , HD 186427 ) , taken at McDonald Observatory and at Lick Observatory , have each independently discovered periodic radial-velocity variations indicating the presence of a Jovian-mass companion to this star .
The orbital fit to the combined McDonald and Lick data gives a period of 800.8 days , a velocity amplitude ( K ) of 43.9 m s ^ { -1 } , and an eccentricity of 0.63 .
This is the largest eccentricity of any planetary system discovered so far .
Assuming that 16 Cygni B has a mass of 1.0M _ { \odot } , the mass function then implies a mass for the companion of 1.5 / \sin i Jupiter masses .
While the mass of this object is well within the range expected for planets , the large orbital eccentricity can not be explained simply by the standard model of growth of planets in a protostellar disk .
It is possible that this object was formed in the normal manner with a low eccentricity orbit , and has undergone post-formational orbital evolution , either through the same process which formed the “ massive eccentric ” planets around 70 Virginis and HD114762 , or by gravitational interactions with the companion star 16 Cygni A .
It is also possible that the object is an extremely low mass brown dwarf , formed through fragmentation of the collapsing protostar .
We explore a possible connection between stellar photospheric Li depletion , pre-main sequence stellar rotation , the presence of a massive proto-planetary disk , and the formation of a planetary companion .