Extra-solar planets

We review recent developments in the research and observations of extra-solar planets. Up to now (beginning of 1998) a dozen or so planetary bodies have been monitored around other stars. These systems are still quite exotic compared to our solar system: some of the planets orbit pulsars, while others are giant planets very close (< 1 AU) to the central star, or on very eccentric orbits. These pecularities come from the biases of the observational methods used so far to detect these planets. At the time being, no extra-solar Earth around a "normal" star has been detected, nor any Jupiter at several AU from the star. In any event, the detections made so far indicate that solar systems can be quite different from ours.