2007A&A...466..717A

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: 1Myr, 10Myr, 30Myr, 100Myr, and 1Gyr. 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 10⁶yr if the impact involves a 1Myr old planet and up to 10⁸yr if the impact occurs on an older planet (∼30Myr). 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.