To discover and confirm the presence of a planet around stars other than the sun, astronomers wait until it has completed three orbits. However, this very effective technique has its drawbacks since it cannot confirm the presence of planets at relatively long periods (it is ideally suited for periods of a few days to a few months). To overcome this obstacle, a team of astronomers under the direction of the University of Geneva (UNIGE) have developed a method that makes it possible to ensure the presence of a planet in a few months, even if it takes 10 years to circle its star: This new method is described for the first time in the journal Astronomy & Astrophysics.