Washington, Nov 15 : Hidden alien moons that could harbor life can be revealed by the wobbles of their planets, according to calculations by a scientist.
Almost all the 30 known exoplanets that sit within the habitable zone of their stars are gas giants.
"But they might have rocky, possibly Earth-like moons," said David Kipping of University College London.
Kipping's calculations, which will appear in Monthly Notices of the Royal Astronomical Society, show that such moons would reveal their presence when the planet passes in front of its star as viewed from Earth.
A moon would induce a wobble in the planet's orbit, so the planet's position and velocity would differ slightly on each transit.
According to Kipping, existing telescopes could detect an Earth-mass moon around a Neptune-mass gas planet.