Some stars exhibit a regular variation in the degree of red shift in their spectra.
This information has recently hit the media with the conclusion that there must be a massive dark object orbiting these stars. In the past year or so the announcement of new planet discoveries is becoming passe, blase' , even boring. That phenomenon is the red shift variation see in some stars. The article refers to another article published by Nature, the British Journal of Science, and written by David Gray of the University of Western Ontario. Gray suggests that the stars may be vibrating or oscillating in some way and that these oscillations cause the variations in the red shift.