 A study in 2014 by Paul Robertson , <unk> Mahadevan , Michael End , and <unk> Roy concluded that Gliese 581 d is " an artifact of stellar activity which , when incompletely corrected , causes the false detection of planet g . " An additional study concluded that Gliese 581 g 's existence depends on Gliese 581 d 's eccentricity . 
