Many of the most interesting bodies in our solar system are not planets, but the moons that orbit them. They have active volcanoes, hydrocarbon oceans, geysers and oceans at the moon scale buried under icy crusts. And, as far as we can say, the physics of processes that produce large planets should make the formation of the moon inevitable. Given how common the planets are, our galaxy should group from moons.
However, despite some attractive clues, we did not find a clear indication of an orbit moon around an exoplanet. What we have found are some very young exoplanets that seem to have discs forming the moon around them. Now, the James Webb space telescope has obtained a spectrum of the ring training disc around a giant super-jupiter, and found that it was rich in small carbon-based molecules. It is despite the fact that the star that he orbit seems to have a planet formation disc which is mainly water.
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We are looking for exo-moon discs and forming the moon using completely different methods. To locate a real moon, we count on its gravitational influence. At times of his orbit, he will tramp his planet forward to accelerate his orbit; To others, he will retain his planet. This introduces subtle variations from the moment when the planet arrives in front of the star from the point of view of the earth.
(The moon must also block a little more from the star light at different times of its orbit, but this can easily be masked by the variability of the star itself.)
However, the discs forming the moon are only present in the history of an exosolar system. They are a bit like larger versions of Saturn’s rings, but with enough material to condense themselves in moons. During the first millions of years in the history of an exosolars’ system, this material will end up with a combination of dispersed, condensed in moons or fallen into the planet.
