Avatar has become the fastest movie yet to break box office records for hitting US$1 billion in ticket sales. Now astronomers says it could be possible to find an Earth-like world as depicted in the film.
Credit: 20th Century Fox
SYDNEY: Habitable alien moons such as 'Pandora' – the world featured in the blockbuster film Avatar – could be detectable within a decade, says a new study.
In that movie, the fictional, life-harbouring moon is found orbiting a gas giant called Polyphemus, which itself orbits the star Alpha Centauri A.
NASA's Kepler Mission has already shown the potential to detect Earth-sized planets within the Milky Way (see "Kepler telescope finds five new exoplanets").
Detecting Pandora
Until now, astronomers have mainly found Jupiter-sized planets; which are easy to detect because they are so large.
But scientists have begun to speculate that life is also likely to be found on the moons of gas giants, orbiting within the 'habitable zone' of their stars – the region warm enough for liquid water to exist (see "Weird worlds").
"If Pandora existed, we potentially could detect it and study its atmosphere in the next decade," said study author Lisa Kaltenegger, an astronomer at the Harvard-Smithsonian Centre for Astrophysics in Boston, USA.
"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 and some of those may be Earth-sized and able to hold onto an atmosphere," she said.
Planetary transits
Astronomers detect planets orbiting host stars by measuring their transits - partial eclipses which occur when the planet crosses the path of the star.
They then detect if there are moons orbiting the planets by looking for a wobble in the movement of the planet caused by the gravity of its moon.
Given the ideal conditions, Kaltenegger predicts that NASA's James Webb Space Telescope (JWST), set to replace Hubble in 2014, should be able to study the atmospheres of Earth-sized exo-moons and detect key gasses like carbon dioxide and oxygen as well as water vapour.
When Kaltenegger calculated the ideal observing conditions for examining the atmospheres of exo-moons, she discovered that Alpha Centauri A - the system in which Pandora is found in Avatar - would be a perfect target.
"Alpha Centauri A is a bright, nearby star very similar to our Sun, so it gives us a strong signal," she explained.
However, the best candidates to actually find habitable planets or moons in are thought to be red dwarf stars, which are relatively small and cool, and therefore have a closer habitable zone.
According to Chris Tinney, an astronomer from the University of New South Wales in Sydney, Australia, the idea of detecting and studying these moons in Kaltenegger's paper may be feasible, but it will be very hard work.
"We are living in an amazing time"
"A space-based telescope like the planned JWST might be able to do such detection, but it is going to be very, very hard," he said. "In particular, it would take the observation of many transits because the signal from each individual transit would be tiny - as many as a year's worth, or many hundreds of hours of observing."
However, Kaltenegger remains hopeful that discovering life on other planets could soon be within our grasp.
"For now, let's just see what we'll find. If we find massive moons with NASA's spacecraft Kepler, as anticipated, we can put the ideas to the test," she said. "We are living in an amazing time where we can discover new worlds, not just new continents."
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