Two suspected exoplanets, Gliese 581
g and 581d, have been shown to not exist, and are instead misinterpretations of data from starspot activity
. From the article: "Gliese 581g doesn't exist," said lead author Paul Robertson of Penn State University in State College, Pennsylvania. Neither, he said, does another planet in the same solar system, known as Gliese 581d, announced in 2009—less clearly hospitable to life, but still once seen by some astronomers as a possible place to find aliens. ... What's happening, they say, is that magnetic disturbances on Gliese 581's surface — starspots — are altering the star's spectrum in such a way that it mimics the motion induced by a planet. The star itself rotates once every 130 days, carrying the starspots with it; the disputed planets appeared to have periods of almost exactly one half and one fourth of the 130-day period. When the scientists corrected for the starspot signal, both planets disappeared.