Hycean Exoplanets, a new class of hot ocean worlds may support life

Humans are in continuous search for life in other parts of the galaxy, but always limit themselves to the obvious and known observations after looking for earth-like planets (“super-Earths” and “mini-Neptunes”) with livable conditions. But as it turns out, now a team of astronomers has figured out a new category of exoplanets – Hycean Planets – proving life can exist even in those parts of the galaxy which do not look like Earth.

Hycean planets, known for their high temperatures, have ocean-covered surfaces with an atmosphere rich in hydrogen and are much easier to find and observe than similar planets like earth. And according to a new study from the scientists of the University of Cambridge, published in The Astrophysical Journal, claims that even having more extreme conditions than Earth these planets could still theoretically host life as we know it.

Astronomer Nikku Madhusudhan from Cambridge University’s Institute of Astronomy told ScienceAlert that,

“Hycean planets open a whole new avenue in our search for life elsewhere. Few conditions in the oceans of these worlds could be similar to livable conditions thus having similar temperature, pressure, water. Still, there are many questions but the assumption is that if aquatic life can form in the same way in these planets as happen on earth then some biosignatures may be common.”

About 4,500 exoplanets have been traced for now in the Milky way but the information from Kepler (a planet-hunting space telescope) tells that the most frequent types of exoplanets are not even part of our solar system. Planets are considered to be potentially habitable when they are located within the habitable zone (a right distance from the star they orbit so that the liquid water remains stable on the planet and possibly supports life) around the stars they orbit.

Madhusudhan and his team found that Hycean worlds may have a size of 2.6 times the size of Earth, and have mass 10 times more than Earth. These planets can reach atmospheric temperatures of almost 392 degrees Fahrenheit (200 degrees Celsius).

As Madhusudan said,

“Greenhouse warming due to molecular hydrogen is such that planet can have warm livable conditions even if it is at a large distance from the star. For atmospheres like those of earth the main greenhouse gases like H₂O and CO₂ freeze out at smaller distances, making the surface frozen and not habitable.”

Hycean Exoplanets, a new class of hot ocean worlds may support life

One of the most interesting features of these planets is the fact that they have many variations. First that Hycean planets have a larger habitable zone, meaning they could still support life even though they exist outside of the zone where our planet is required to be in order to sustain habitability.

Second, some of these planets may be tidally locked, meaning they permanently have a side that receives daylight from the star it orbits and the other side is perpetually in the dark. In this case, tidally locked Hycean planets may only be habitable on one side.

Madhusudan said in his press statement when they started looking for molecular signs, they were more focused on planets like the earth which seems to be reasonable. But then they thought that Hycean planets may provide higher chances of finding several trace biosignatures.

The team in their paper also said that these worlds can be traced when a specific exoplanet passes between Earth and its star and thus a particular wavelength of light halted by the atmosphere. And where these wavelengths fall is a chemical sign which tells what element compound causes such an effect.

Still, there is much theoretical work that needs to take place, before scientists claim that that life actually exists in any of these Hycean planets.


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