That’s it ! For the first time, thanks to the James Webb Space Telescope, we have seen arguably the most common type of planet in the Universe, a planet absent from our system, but which has inspired many SF stories: an ocean planet.
Hervé Poirier, editor-in-chief of the scientific magazine Epsiloon, speaks to us today of a type of planet that the screenwriters and authors of SF have long imagined, an ocean planet.
franceinfo: Immersed in a new type of world, so can you explain?
Herve Poirier: Think for example of the planet Kamino, where the clones come from in episode 2 of Star Wars. or at Aquaendthe prison planet drawn by Moebius, in the comics The incal. Not to be confused with water world by Kevin Costner, which is an Earth with rising sea levels. No: imagine a planet made up of 50% water – it’s 0.1% for ours. Imagine a planet a little smaller than Neptune, completely covered by an ocean several hundred kilometers deep, above a rocky base…
It has only been twenty years since planetary scientists developed models of the formation of these fantastic stars. But, for the past fifteen years, given the mass and size of the thousands of planets detected, they believe that this is the most common type of planet in the Universe. There would be an ocean planet around one out of two stars! It therefore remained to really detect one, beyond the shadows that telescopes see pass in front of the stars.
And this is what has just been done?
Yes, thanks to the famous James Webb space telescope, the JWST. They directed it towards GJ 1214b, located about forty light years from here – the Hubble telescope had spent hours observing it in vain. JWST was able to observe how the temperature of the planet varies between day and night. He was also able to see that its atmosphere is not made up of hydrogen and helium, like Neptune, but of heavy elements. It could certainly be methane, but several clues show that it is rather water vapor: GJ 1214b is very probably the first ocean planet ever detected.
And who says water… says life? GJ 1214b could be inhabited?
No. She’s way too hot. And the question of whether ocean planets can give rise to life remains open. The exploration of this new type of world has only just begun. In Star Wars, Kamino is the home planet of an intelligent species renowned for the quality of the clones they supply to the Galactic Republic. But there, we went right back into SF.