In 2021, astronomers proposed a new class of exoplanets that contain hydrogen-rich atmospheres and support vast oceans of liquid water, making these hypothetical worlds potential candidates in the search for alien life. However, a new study shows that Hikean type planets will be catastrophic greenhouse effectthis limits their potential to survive.

The Hycaean worlds get their name from the combination of “water” and “ocean” because they are larger than Earth but smaller than any of the giant planets in our solar system, covered in thick, dense layers. hydrogen. atmosphere and can support vast oceans of liquid water.

Although the existence of Hycaean worlds has not been confirmed, extensive research has exoplanets driven by the mission NASA’s Kepler has discovered several candidate worlds that could be Hickian planets based on size and density estimates.

Astronomers are very interested in the Hycaean worlds. Where there is liquid water, there is a potential home for life as we know it. And thanks to their dense atmospheres, these planets could potentially exist around their parents in a much wider range of orbits. stars without compromising habitability, so life on the Hykean worlds is likely to be more common than ours.

However, current research on the habitability of Hyckeian worlds is not very detailed, relying on relatively simple models of atmospheric dynamics to understand how these planets work. To remedy this, the team of researchers developed a more sophisticated approach to study how more precise treatment of Hycaean atmospheres and oceans would change our understanding of their behavior around different types of stars.

“Supercritical” oceans

The researchers found that the presence of a thick, hydrogen-dominated atmosphere radically changed the behavior of these planets compared to a similar world. Soil. Our planet also has a thick atmosphere, but this atmosphere is made up of heavier elements such as nitrogen and oxygen. The ability of these elements to block or transmit light of certain wavelengths affects how hot a surface is for a given amount of incoming solar radiation.

But hydrogen works differently: it blocks and transmits light of different wavelengths, which changes the surface’s response to sunlight. For example, the researchers found that if a planet with an atmospheric pressure of 10 to 20 times that of Earth (typical of Hyckeian worlds) were placed in the same orbit as Earth, its oceans would become “supercritical.” This means that the planet’s temperature will rise above its boiling point, which will lead to the evaporation and complete destruction of the oceans.

The researchers also found that the mixture of water vapor and hydrogen in the atmospheres of Hycaean planets altered habitability. Hycaean worlds don’t get as much sunlight as we thought before their oceans got too hot to carry them as liquids.

On the inner border of the saloon in previous models regions, the region where the planet’s surface temperature is sufficient to support liquid water was located at the exact circumference of one astronomical unit (AU), the distance the Earth revolves around the Sun. But the new calculations increase the inner edge to 1.6 AU for worlds with Earth-like air pressures. For Hycaean worlds with 10 times atmospheric pressure, the inner limit of the habitable zone is now considered to be 3.85 ao.