Exoplanet Detection by Astrometric Method

As we know, the exoplanets are mostly detected by the methods of radial velocity and transit, up to now only one is found by the astrometric method. As the data of the gaia will be soon released, astrometry will gradually become one of the most important methods for detecting exoplanets. Based on the sequence of star positions obtained by the astrometric method, the solution of the equations of dynamical conditions involving the calculations of planet's mass and orbital parameters is discussed in this paper. Due to the deficiency of the available theory (orbital element method), a new method (coordinate velocity method) is put forward. The differential correction formulae of the two methods, as well as the necessary simulation calculations are presented. In addition, the method established in this paper can be applied to the multi-planet system easily.