High precision radial velocity ( RV ) measurements spanning the years 1980.8–2000.0 are presented for the nearby ( 3.22 pc ) K2 V star \epsilon Eri .
These data , which represent a combination of six independent data sets taken with four different telescopes , show convincing variations with a period of \approx 7 yrs .
A least squares orbital solution using robust estimation yields orbital parameters of period , P = 6.9 yrs , velocity K -amplitude = 19 m s ^ { -1 } , eccentricity e = 0.6 , projected companion mass M sin i = 0.86 M _ { Jupiter } , and semi-major axis a _ { 2 } = 3.3 AU .
Ca II H & K S-index measurements spanning the same time interval show significant variations with periods of 3 and 20 yrs , yet none at the RV period .
If magnetic activity were responsible for the RV variations then it produces a significantly different period than is seen in the Ca II data .
Given the lack of Ca II variation with the same period as that found in the RV measurements , the long-lived and coherent nature of these variations , and the high eccentricity of the implied orbit , Keplerian motion due to a planetary companion seems to be the most likely explanation for the observed RV variations .
The wide angular separation of the planet from the star ( approximately 1 arc-second ) and the long orbital period make this planet a prime candidate for both direct imaging and space-based astrometric measurements .