The outer solar system holds some chunks of ice and rock that orbit so far from the sun it’s hard to imagine how they got there – but an ancient rogue planet may hold the key
Getty Images/iStockphoto/Ahmad Sarem
A rogue planet twice the size of Earth may have pushed asteroids into the outer reaches of the early solar system before it was ejected. This could solve the mystery of how some of the most distant objects in the Kuiper belt got there, which cannot be explained by most models of solar system formation.
The Kuiper belt is a huge disc of cold rocks and ice that extends out beyond the orbit of Neptune. …