`Habitable moons like in film `Avatar` could be real`

James Cameron`s science fiction `Avatar` may become fact in the coming years, says a leading US astronomer.

Updated: Dec 21, 2009, 21:20 PM IST

London: James Cameron`s science fiction `Avatar` may become fact in the coming years, says a leading US astronomer who believes there is every chance a real-life version of habitable alien moons like the one depicted in the movie exists and will soon be found.

The 3D blockbuster shows a race of blue-skinned giants inhabits an Earth-like moon called Pandora, which orbits a gas giant planet similar to Jupiter that cannot support life.
"If Pandora existed, we potentially could detect it and study its atmosphere in the next decade," said Lisa Kaltenegger, an astronomer from the Harvard-Smithsonian Centre for Astrophysics in Cambridge, Massachusetts.

Kaltenegger, who has conducted research showing that a planned new space telescope will be able to identify nearby "exomoons" and discover if they are habitable, said hundreds of Jupiter-sized gas giants orbiting stars have already been spotted, but none have conditions suitable for Earth-type life, The Telegraph reported.

However, a rocky moon orbiting a gas giant could harbour life if it was in the parent star`s "habitable zone" – the region where temperatures are just right for liquid water, she said.

"All of the gas giant planets in our solar system have rocky and icy moons. That raises the possibility that alien Jupiters will also have moons. Some of those may be Earth-sized and able to hold onto an atmosphere," she said.
A Pandora-type moon could be identified when its planet "transits" across the face of the parent star. If the moon has an atmosphere, this will absorb a tiny amount of light from the star, leaving a spectrographic fingerprint of its composition.

Dr Kaltenegger calculated that Alpha Centauri A, the star featured in Avatar, would provide an excellent target for astronomers hunting habitable moons.

Alpha Centauri is the closest star system to the Sun, being only 4.37 light years away. It consists of three stars, the largest being Alpha Centauri A, which is slightly brighter than the Sun.

"Alpha Centauri A is a bright, nearby star very similar to our Sun, so it gives us a strong signal. You would only need a handful of transits to find water, oxygen, carbon dioxide and methane on an earth-like moon such as Pandora.

"If the Avatar movie is right in its vision, we could characterise that moon with JWST in the near future."
She said small, dim red dwarf stars may provide the best evidence of habitable planets or moons. This is because the habitable zone for a red dwarf is closer to the star, which increases the likelihood of a transit as seen from the earth.

Red dwarfs are also the most common kind of star in our galaxy, the Milky Way.

"Alien moons orbiting gas giant planets may be more likely to be habitable than tidally locked Earth-sized planets or super-Earths," said Dr Kaltenegger. "We should certainly keep them in mind as we work toward the ultimate goal of finding alien life."

Dr Kaltenegger`s research is published online in Astrophysical Journal Letters.