The solar system’s mightiest planet (Image:University of Arizona/JLP/NASA)

JUPITER might have secured its position as the solar system’s mightiest planet by killing an up-and-coming rival, new simulations suggest. The work could explain why the planet has a relatively small heart, and paints a grisly picture of the early solar system, where massive, rocky “super-Earths” were snuffed out before they could grow into gas giants.

Jupiter and Saturn are thought to have begun life as rocky worlds with the mass of at least a few Earths. Their gravity then pulled in gas from their birth nebula, giving them dense atmospheres. …