Microlensing
Another method is microlensing. It makes use of MACHOs, Massive Astrophysical Compact Halo Objects, by using them as gravitational lenses for the star. That is, the MACHO magnifies the light from the star. For a star lacking in planets, the result is a gradual increase in brightness, the light curve having characteristics that distinguish it from variable stars, namely the symmetry in time and the same magnitude before and after the event. A star that does have companions therefore should have small perturbations in its light curve due to the planets. The problem with this is that it needs the MACHO to be passing in front of the star at the same time the planet is in a position to effect the light being lensed. For example, it needs to be moving from behind the star to increase the light coming from the system after the lensing has begun.