A feature of this method is that it requires to detect at least three successive transits separated by two equal time intervals before one can consider a target as a serious candidate. A planet of orbital period "T" should at least be observed for a time interval between 2"T" and 3"T" to have a chance to detect three transits. The distance of the planet to the star ( which is characterized by "a" the semi-major axis of the elliptical orbit ) is linked to its orbital period by the second law of Kepler / Newton "a"3 = "T"2 Mstar, using respectively as units for "a", M and "T": the distance from the Earth to the Sun (150 million km), the mass of the Sun, the orbital period of the Earth (1 year); this implies that if the observing time is less a year, for example, the orbits of the detectable planets will be significantly smaller than that of the Earth.