THE HUNT FOR FARAWAY MOONS

Astronomers are looking for moons outside our Solar System that may have even more chance of hosting life than the planets they're orbiting

- COLIN STUART

Long ago, the prospect of far-off inhabited planets was solely the domain of science-fiction writers. Famous tales abound of Time Lords from Gallifrey, superheroes from Krypton and hammer-wielding gods from Asgard, to name but a few. Given the number and variety of exoplanets – or planets outside of our Solar System – now being found by astronomers, fiction is fast falling into alignment with fact. But as well as planets, science fiction also tells of life thriving on the moons of exoplanets, or ‘exomoons’. Notable examples include the forest moon of Endor, home to the Ewoks in Star Wars, and the tree-covered Pandora in Avatar. Now, just as they did with exoplanets, telescopes are starting to bring exomoons into the realm of reality.

“We were looking for exoplanets using a technique called microlensing,” said David Bennett, an astronomer at NASA’s Goddard Space Center. But using this technique, Bennett may have had the first-ever glimpse of a moon outside our Solar System.

Microlensing is a method that exploits the fact that gravity bends light. If an object passes in front of a distant star, its gravity focuses the starlight like a lens and the star’s brightness temporarily shoots up. In research published in 2014, Bennett revealed that, using the MOA-II telescope in New Zealand, he’d seen a sharp rise in a star’s brightness, followed an hour later by a second, smaller increase. He deduced that a large object must have passed in front of the star with a smaller object in tow, hence the second spike.

EXTENDED HABITABLE ZONES