Photometric stellar variation due to extra-solar comets

We performed numerical simulations of stellar occultations by extra-solar c ometary tails. We find that extra-solar comets can be detected by the appar ent photometric variations of the central stars. In most cases, the light c urve shows a very peculiar "rounded triangular'' shape. However, in some ot her cases, the curve can mimic a planetary occultation. Photometric variati ons due to comet occultations are mainly achromatic. Nevertheless, if comet s with small periastrons have smaller particles, these occultations could b e chromatic with a larger extinction in the blue by few percents. We also estimate the number of detections expected in a large photometric;s urvey at:high;accuracy. By the observation of several tens of thousand of s tars, it should be possible to detect several hundreds of occultation per y ear. We thus conclude that a spatial photometric survey would detect a larg e number of extra-solar comets. This would allow to-explore the time evolut ion of cometary activity, and consequently would probe structure and evolut ion of extra-solar planetary Systems.