Cambridge astronomers propose a new category of habitable exoplanets

Researchers at the University of Cambridge, UK, suggest that the search for planets with life should not be limited to worlds similar to ours, and believe that a certain category of these objects is a candidate for the first detection of biosigns: the Hycean planets.

Strange name, isn’t it? It took me a while to understand where it was coming from. Hold on when I get there. Much has been said about ocean planets that were slightly larger than Earth and completely covered by thick layers of water that could make our seas look like swimming pools.

And then the next, so far little-regarded category would consist of even larger planets which, in addition to the abundance of water, would have extensive atmospheres dominated by hydrogen, similar to those of giant gas planets.

In both cases we speak of worlds with an intermediate size between the earth (the largest of the rocky solar worlds) and Neptune (the smallest of the gaseous worlds, with a diameter about four times larger than that of the earth). There’s nothing quite like it in the solar system, but astronomers have found hundreds of planets with diameters in this mid-range, and they’re commonly called super-earths (up to 60% larger than Earth) or mini-neptunes (if more than 60%).

Until recently, mini-neptunes, although more numerous than super-earths, were considered poor candidates for harboring life. It has been speculated that the pressure and temperature under its hydrogen-rich atmosphere were too high to allow life.

The game started turning last year when Nikku Madhusudhan’s team at Cambridge showed in a study published in Astrophysical Journal Letters that the mini-Neptune K2-18b, discovered by NASA’s Kepler satellite, despite its 2.6 times the size of the earth theoretically have a habitable ocean under its hydrated atmosphere. Hydrogen + oceanic, hyceanic. Frog.

Now Madhusudhan and his colleagues Anjali Piette and Savvas Constantinou present the category of the Hycean planets more broadly in a new article, this time in the Astrophysical Journal. In theory, worlds up to 2.6 times the Earth’s diameter can maintain habitable conditions, and the so-called habitability zone (region around the star in which the amount of radiation is compatible with the existence of stable bodies of water on a planet) would be much wider for these worlds than for terrestrial ones Analogues.

And most excitingly, the atmosphere of many potential Hecean planets could very soon be examined in detail by the James Webb Space Telescope, which NASA plans to launch by the end of the year. By the way, observations from the K2-18b should already be among the first to be carried out by the new satellite.

This column is published in Folha Corrida on Mondays.

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