Observational signatures of the giant planets collisions
  We consider observational signatures of the collisions and partial destructions of giant exoplanets at the chaotic stage of the planetary systems evolution. The rate of these collisions in the Galaxy is estimated to be ~0.01-1 per yr. In the inelastic collision with a small relative velocity and small impact parameter, the planets may sufficiently lose their kinetic energy and merge together. Otherwise, if the planet is experienced a shallow tangential collision, it flews safety away. At the same time, the planets loss some part of their gas envelopes during mutual collisions. Collisions of the giant planets must be accompanied also by the radiation of energy from the radio to optical bands. The optical and near UV flashes result from the collision heating of the planet surface layers. Additionally, the collision compression and collapse of the powerful magnetosphere of giant planets are possible, with a successive generation of the radio bursts. According to our estimations, the corresponding rate the radio bursts is ~0.01-1 bursts per year with the maximum spectral flux ~30mJy at the frequencies ~3GHz and with a duration of the each burst ~1.5 hours. These signals are available for registration by the existing radio telescopes. 
V.I. Dokuchaev, Yu.N. Eroshenko
astro-ph.EP