London, Jan 13 : After searching for planets outside our solar system, scientists have now devised a way to detect exomoons.According to a report in Nature News, the method, devised by astronomer David Kipping of the University College of London, involves a way to spot the effects of a moon on the path of the planet it orbits.
The effect can be seen when the planet passes between us and its star. This is called a transit, and it is a common way of spotting exoplanets.
If a planet has a moon, each transit has a slightly different position and velocity, creating a wobble in the planet’s orbit.
Kipping said that his method complements an existing technique for spotting extrasolar bodies called transit time variation (TTV), which measures the time between consecutive transits.
Variation in this time is not a smoking gun for an exomoon, because it has a number of possible causes, including another planet in the system.
Besides happening at irregular intervals, the transits of a planet with a moon will vary in their duration, speeding up and slowing down. Kipping calls this effect the transit duration variation (TDV).
Another planet, on the other hand, will always lengthen the transit, because the second planet will always be traveling in the same direction as the transiting one.
Furthermore, because velocity is related to mass, TTV and TDV can be used together to work out the mass of the moon.
According to astronomer Jean Schneider at the Laboratory of the Universe and Theories near Paris and a developer of the TTV model, the TDV method will help to distinguish between the effects of moons and planets.
Schneider is trawling through data from the Convection, Rotation and Planetary Transits (COROT) mission, the European Space Agency’s space-based telescope searching for transiting exoplanets.
So far, he has not seen a signal that might be a moon, but the mission will run for at least another two years.
“I am sure that we will detect a moon before 2015,” said Schneider.
Once a moon is found, the question of habitability can be looked at. Most exoplanets found so far have been gas giants, which are inhospitable to life.
“One of the big problems with gas giants is they don’t have rocky surfaces,” said Kipping. Moons of these planets, on the other hand, could be quite different.
“I think it is time to speak about supermoons,” said Schneider. “Some day, we will find large moons, much larger than Titan and larger than Earth,” he added. (ANI)
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