Canadian astronomers using the MOST (Microvariability & Oscillations of STars) Space Telescope have detected that a giant extrasolar planet has forced its parent star into a lock-step orbit. This interaction is between the star tau Bootis and its "hot Jupiter" planet discovered in 1997. MOST was able to detect subtle variations in the star's brightness that correspond with the planet's orbit. It's likely that the planet has forced the outer layer of tau Bootis' atmosphere so that it rotates to keep the same side facing.