Avatar's moon - Pandora - could exist in reality say planet hunters

The Kepler space telescope may discover planets the size of the Earth, and the James Webb telescope that will be launched in a few years will even be able to locate moons and analyze their atmospheres, under certain conditions, thus a life-bearing moon such as Pandora in the movie Avatar, may exist in reality. This is according to an article published this week

In Hollywood's new blockbuster movie Avatar, humans visit a habitable but uninhabited alien moon called Pandora.

Life-bearing moons such as Pandora or the forest moon of Endor in the Star Wars film series are examples from the realm of science fiction. However, following the launch of NASA's Kepler telescope, it will be possible to discover Earth-sized planets, and it is possible that habitable moons will become a real science.

If we find them very close to Earth, says an article published by Lisa Kaltenger, an astronomer at the Smithsonian Institution for Astrophysics, the James Webb Space Telescope, which will be launched in a few years, and which will replace the Hubble Hillel Telescope, will be able to study their atmospheres and discover important gases such as carbon dioxide , oxygen and water vapor.

So far, exoplanet hunters have discovered hundreds of Jupiter-like and larger planets in a wide variety of orbits. Gas giants, which are very easy to discover, cannot serve as a home for life as we know it. And yet the scientists estimate that if rocky moons exist around them, they could be friendly to life. This is of course, if the moon's orbit is within the star's habitable zone - the zone that is warm enough to support liquid water, but not too hot.

"All the gas giants in the solar system have rocky moons and ice moons," Kalenger says. "This raises the possibility that planets in other Jupiter-like systems also have moons. Some of them may be the size of the Earth and hold an atmosphere.”

Kepler will look for planets that cross in front of their sun, which creates a mini-eclipse and dims the starlight by a small but distinguishable amount. Such a transit only takes a few hours and requires precise alignment of the star and planet in our line of sight. Kepler will examine thousands of stars and, because of these limitations, may find only a few planets transiting in front of their star.

Once alien planets are found, astronomers can search for moons around them. The gravitational force of that moon will hold the planet and speed up or slow down its transit, depending on whether the moon is ahead or behind the planet in its passage near the sun. The changes in the transit speeds between different transits are the ones that will testify to the presence of the moons.

Once such a moon is found, the next obvious question is whether it has an atmosphere. If the answer is yes, these gases will absorb some of the starlight during the transit, leaving a small fingerprint of the composition of the atmosphere.

These signals will be strong when it comes to large worlds with hot, inflated atmospheres, but Earth-sized moons can only be studied if the conditions are precisely right. For example, the separation between the moon and the planet must be large enough so that we can only capture the moon in transit, while the planet is in another measure of the star.

Ketlinger calculated what the best conditions are for studying the atmosphere of alien moons. She found that Alpha Centauri A, the system where the movie Avatar takes place, might be a good target.

Alpha Centauri A is a bright star relatively close to the sun and very similar to it, so these facts give us a good sign to continue. "All it takes is to track a number of passes, find water, oxygen, carbon dioxide and methane on a Pandora-type Earth-like moon."

If the vision shown in the movie Avatar is true, we will be able to characterize the moon with the James Webb telescope already in the near future.

While Alpha Centauri A provides tantalizing possibilities, dim small stars – especially red dwarfs – are better targets for searching for habitable planets or moons. The habitable zone of these stars is closer to the Sun, which increases the likelihood of these transits.

Astronomers debated whether tidal waves could be a problem for red dwarfs. A planet that moves close enough to be in the habitable zone of a red dwarf may be close enough that the star's gravity slows it down until it only shows one side (like the situation in the Earth-Moon system). One side of the planet will be permanently basked in sunlight, while the other side will be frozen in eternal darkness.

A moon orbiting a planet in the habitable zone of a red dwarf could be saved from this dilemma. It will be gravitationally bound to the planet, not to the star itself, so it will have cycles of day and night, like in the Orb. Its atmosphere would be moderately warm, and the plants could be a good source of energy for the entire moon.

"Alien Earth-sized moons orbiting gas giants would be a better place for life than gravitationally trapped Earth-like or super-Earth planets," Ketlinger says. "We will have to remember this when we work on our final goal - discovering life outside the Earth."

For information on the website of the Harvard Smithsonian Institute for Astrophysics