Habitable planets may be lurking in the wake of Jupiter-like planets as they orbit distant stars.

When a gas giant coalesces from the swirling nebula of gas and dust surrounding a young star, the planet's gravity forms a wake ahead and behind it, concentrating enough matter there for it to clump together and form smaller, rocky planets like Earth.

That's according to simulations led by Wladimir Lyra of the Uppsala Astronomical Observatory in Sweden. Objects born in Jupiter's wake may have merged to form the planet Saturn, which was then nudged into its current position by the gravity of other planets, the team says.

Outside our solar system, some gas giant planets have been detected in the habitable zone of their stars. Their wakes may harbour rocky, Earth-size worlds. "It's an exciting possibility," says Sara Seager of MIT.

She notes that such planets could be found by the small gravitational tugs they exert on their larger, known siblings, an idea supported by recent calculations by Nikku Madhusudhan and Joshua Winn, also of MIT.