## The G2 Systems and Gliese 777A

By giving a few examples of systems where the GG orbits its host star in such a distance that a TP could move in the HZ which would be well inside the GG's orbit we will describe five EPS and one of them in a more detailed fashion. Here we would like to follow the results described in Asghari et al. 12 . The computations in the aforementioned article were performed with orbital elements known at that time in Table 2.1 we show the new data derived from recent observations also. One can see the...

## Radial Velocity in Astrocentric Elements

The observation of a Doppler shift of the spectral lines of a star denounces a change in the velocity of the star with respect to the observer. Since the observer himself is moving with a velocity 30 km s_1, variable in direction, it is necessary to subtract this motion from the observational data and reduce it to the barycenter of the solar system for a description of the necessary operations see Ferraz-Mello et al. 2 . The velocity of an isolated star, with respect to the barycenter of the...

## Comparisons Between Coordinate Systems

We have seen that, at least formally, the Poincare formalism is simpler and more compact than the Jacobi variables. But how does each perform in practice We have simulated the short-term orbital evolution of a co-planar system formed by a central star with m0 0.32M and two planets with masses m1 20MJup and m2 5MJup. Initial conditions were chosen such that both planets have circular orbits with semi-major axes a1 0.131 AU and a2 0.232 AU and are in opposition. The large planetary masses were...