Exoplanet K2-18b Could Be a Hycean Water World That Supports Life, JWST Observations Reveal

The exoplanet K2-18b has just gotten more interesting as observations made by the James Webb Space Telescope show that it could be a Hycean world that is capable of supporting life.

Exoplanet K2-18b

For a long time, astronomers have harbored interest towards the exoplanet K2-18b. It became the first rocky world in the habitable zone that was found to have water. The habitable zone refers to the planet's distance from its host star at which liquid water could exist over its surface.

Unlike the Earth, K2-18b is remarkably heftier. In fact, it has a mass that is equivalent to 10 Earths and a radius of 2.6 Earth radii. K2-18 also fully accomplishes its orbit around a red dwarf star in 33 days.

However, compared to the Sun, red dwarf stars are dimmer and cooler. Hence,the stellar irradiation K2-18b receives is similar to Earth.

A Possibly Habitable Hyacean World

Nikku Madhusudhan, an astronomer from the University of Cambridge, and his team looked into the exoplanet back in 2020 and discovered the possibility of habitability. They also identified in 2021 that the exoplanet could be a Hycean world.

However, the team needed more data. They needed the help of the James Webb Space Telescope to examine the exoplanet's atmosphere more closely and detect signs.

With the help of the NIRISS and near-infrared NIRSpec instruments of the JWST, they observed two orbits of K2-18b between the Earth and its host star. They looked into the variations in the light of the star as a result of movement and after being affected by the atmosphere of the exoplanet.

Upon teasing apart the alterations, the specialists discovered evidence of methane, carbon dioxide, and carbon molecules. The light spectrum also showed hints of dimethyl sulfide.

While these observations are not sufficient to make a conclusion regarding the habitability of the exoplanet, it leads scientists a step closer to finding out. Madhusudhan explains that further JWST observations should help in confirming the presence of dimethyl sulfide in K2-18b's atmosphere.

Moving forward, the next step would be to face the mid-infrared MIRI of JWST to K2-18b. This will be done to take a deeper look and check the possible presence of dimethyl sulfide and to find other potential biosignatures in the atmosphere of the exoplanet.

The results also show the capacity of the Webb telescope to pick up biosignatures in the atmospheres of exoplanets. This is a crucial step in detecting life in other worlds. As Madhusudhan explains, their ultimate aim is to identify life on an exoplanet that is habitable. He adds that their results are a crucial step towards having a better understanding of Hycean worlds.

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