Giant collisions involving young Jupiter

We present high-resolution, three-dimensional simulations using a smooth particle hydrodynamics (SPH) code of giant impacts involving young Jupiter-like planets. Our aim is to explore the effect of such impacts on the structure and evolution of the planet and discuss the likelihood of detecting these post-impact planets. For this, we considered head-on and off-axis impacts by an Earth-like planet onto a young Jupiter at five different ages: 1 Myr, 10 Myr, 30 Myr, 100 Myr, and 1 Gyr. We briefly discuss the short-term post-impact evolution and concentrate on computing the long-term cooling of the planet. We find that the bright IR afterglow lasts for about 106 yr if the impact involves a 1 Myr old planet and up to 108 yr if the impact occurs on an older planet (~30 Myr). We estimate that, about 10 to 100 young planetary systems must be observed to detect one candidate for such post-impact object. Given that their luminosity is only increased by a roughly 50%, this frequency does not make them ideal observing targets. We note nevertheless that the detection of this kind of post giant-impact planet would represent an important milestone in observationally establishing the current planet formation theories that are based on collisions.