A planet-seeking spacecraft launched in March is so powerful that it will even detect habitable moons around alien worlds, UK scientists said today.

NASA’s $595 million Kepler mission is flying through space checking out 100,000 stars looking for other planets resembling Earth.

Its instruments scan the light of stars in one small region of the Milky Way, watching for little blips revealing that a planet is passing in front of one of them.

Now a team led by Dr David Kipping of University College London says they may even find habitable moons too. They will be able to support alien life if they live in the “Goldilocks zone” around a star where conditions are not too hot or cold but just right.

Dr Kipping, who believed that many thousands or even millions of these moons exist in the galaxy, has devised a way to discover them by looking for a wobble in the planet that each is orbiting, due to its gravitational pull. The new research shows that Kepler’s telescope will be powerful enough to spot the changes in the planet’s position and velocity.

An alien solar system’s moon – dubbed an exomoon – will be easiest to detect if it is orbiting a fluffy planet like Saturn, say the scientists, rather than a more dense or solid world. This is because Saturn’s lightness would make it wobble much more than a heavy planet.

If the Saturn-like planet is at the right distance from its star, then the temperature will allow liquid water to be stable on any sufficiently large moons in orbit around it and these could then be habitable.

The team found that moons as small as a fifth the weight of the Earth should be easily detectable with the Kepler spaceprobe around 25,000 stars up to 500 light-years away from Earth.

Star Wars fans are already wondering if Kepler might find planetary satellites like the fabled Forested Moon of Endor, the planet that was home to the Ewoks.

Dr Kipping said: “For the first time, we have demonstrated that potentially habitable moons up to hundreds of light years away may be detected with current instrumentation.

“As we ran the simulations, even we were surprised that moons as small as one-fifth of the Earth’s mass could be spotted. It seems probable that many thousands, possibly millions, of habitable exomoons exist in the Galaxy and now we can start to look for them.”

The team’s findings will be published by the Royal Astronomical Society. Last month, Skymania News told how Kepler had detected the phases of an extrasolar planet.

Picture: Artist Dan Durda’s impression of the scne from a moon orbiting an extrasolar planet. (Credit: Dan Durda, Southwest Research Institute).

• Discover space for yourself and do fun science with a telescope. Here is Skymania’s advice on how to choose a telescope. We also have a guide to the different types of telescope available.