A team led by Nikku Madhusudhan, an astrophysicist and exoplanetary scientist at the University of Cambridge, proposed that these relatively overlooked planets “can be optimal candidates in the search for exoplanetary habitability and may be abundant in the exoplanet population,” according to a study published on Wednesday in The Astrophysical Journal. What’s more, Hycean planets are much easier to observe and characterize compared to Earth-like rocky worlds, which means they could be scanned for signs of life by next-generation observatories, such as the James Webb Space Telescope, within the next few years.
“Up until now, whenever you hear about habitable planets, you’re basically picturing an Earth 2.0,” Madhusudhan said in a call. “You’re picturing an Earth-like planet with an Earth-like atmosphere and surface and you put it around the star at the right temperature so you can have liquid water. That has been our canonical notion of habitability.”
Hycean planets, in contrast, are about two to three times bigger and up to 10 times more massive than Earth, placing them within other exoplanetary categories such as “super-Earths” and “mini-Neptunes.”
Though our own solar system lacks any planets in this size range, they are extremely common in other star systems, which has led to cautious speculation about whether they might be able to host life. These worlds could have extensive oceans of liquid water, which is a plus for habitability, but their huge masses may create pressures that are simply too high to support life. Their thick hydrogen atmospheres can also reach sweltering temperatures of 200°C, suggesting that many of these worlds are too hot to be habitable.
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