Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581

Abstract

Tricky star plays sleight-of-light Two signatures in starlight thought to be written by extrasolar planets may turn out to be forgeries. Astronomers often attribute periodic shifts in a star's apparent motion toward and away from us to the tug of orbiting planets. Robertson et al. studied archival spectra of the star Gliese 581 to assess another potential cause: magnetic activity on the star's surface. The signals once attributed to two planet candidates instead resulted from the combined effect of starspots and stellar rotation. Planet hunters be warned—correct for stellar activity in your data analyses. Science , this issue p. 440