Up to present date, no circumbinary planet around contact binaries were discovered neither by transit method nor by the minima times variation, although they are known having third component stars around. We thus ask: where are the circumbinary plane
ts of contact binaries? By considering the physical and geometrical parameters we simulated the light curves of contact binaries with possible transiting circumbinary jovian planets. It seems either the circumbinary jovian planets are not formed around contact binaries, probably due to dynamical effects of the binary and third component stars, or they are present but the discovery of such planets were not possible so far due to larger distortions then expected in the photometric data and in the minima times.
The period changes of contact binaries obtained by the analysis of eclipse minima timing are found mostly chaotic in nature. However, they are representable by a few cyclic changes superposed on a secular change. The cyclic changes are caused most pr
obably by the third components revolving around the contact binaries. Some typical examples of the period changes of contact binaries are presented in the present contribution.
