because the suspected planets are lost in the glare of the stars they orbit,they could not actually be seen.Instead,the astronomers analyzed the shifts of light in the spectrum associated with a star as it moves.A shift toward red means the the source is moving away from the observer,toward blue that it is moving toward him.By careful measuring these colour shifts,astronomers detected a characteristic wobble in the motion of the stars that could be caused by the gravitational pull of a nearby orbiting body.