The key observation was that the Nu Octantis planet is retrograde – the planet and one star both orbit the second star, but they do so in opposite directions, with the planet having the tighter orbit around the second star. So, the planet either used to orbit both stars at once, but then radically shifted trajectory when one of the two stars became a white dwarf, or it was formed from the mass that the star ejected as it transformed into a white dwarf. For centuries, star watchers have been used to neat cosmic arrangements like the solar system where all planets orbit a central star in the same direction and with temperate spacing, but Nu Octantis breaks all such conventions, says Manfred Cuntz at the University of Texas at Arlington.