Probably you have already heard of the exoplanet “K2-18b” since we briefly introduced it in the article about the James Webb Telescope. If you haven’t read it, go check it out! However, did you know this exoplanet is so special because it has shown hints of life?
Exoplanets are planets outside our solar system that orbit around other stars. In the case of K2-18b, the planet orbits around a red dwarf star called K2-18. As you may have noticed, the name of the exoplanet is directly related to the star it orbits around, “b” refers to the first planet found, “c” to the second and so on.
124 light years away, K2-18b was first observed back in 2015 by Kepler, NASA’s first planet-hunter mission. Launched in 2009 and retired in October 2018, the telescope unveiled billions of exoplanets that may contain traces of life and among these planets there was K2-18b. But why is NASA so focused on K2-18b?
Kepler’s first observations showed that K2-18, the red dwarf, would give around 1,220 W/m2 of radiation to K2-18b, which is around the same that the Earth receives from the sun (1,360 W/m2). Even though the star is less powerful, the distance plant-star is shorter, making the amount of energy comparable. Since it has not considered the atmosphere, the temperature of the surface was unknown. Nevertheless, Kepler’s observations offered a promising start!
In 2019, the Hubble Space Telescope detected signs of water vapor. Water vapor may indicate water on the surface and thus the appropriate surface temperature to sustain life.
Recently, thanks to the James Webb Space Telescope (JWST), new data from K2-18b was obtained. The telescope revealed carbon-bearing molecules (i.e. methane and carbon dioxide) making K2-18b a possible Hycean exoplanet. This means that it has the potential to contain a hydrogen-rich atmosphere. There’s one thing to consider though; the measurements from the JWST were not very strong and the biosignatures detected may have been affected. This does not mean that they are not there, it’s just that we don’t have enough information to confirm the presence of biomarkers, thus the possible presence of life.
What will future data from K2-18b tell us?