What can sub-Neptune exoplanets teach astronomers about finding life beyond Earth? This is what a recent study published in The Astronomical Journal hopes to address as a team of scientists investigated the likelihood of the sub-Neptune exoplanet, K2-18 b, of having conditions for life as we know it. This study has the potential to help scientists better understand a particular class of sub-Neptunes known as “hycean” planets, which have hydrogen atmospheres with liquid water oceans beneath them.
For the study, the researchers analyzed data obtained from NASA’s James Webb Space Telescope (JWST) to conduct follow-up observations of K2-18 b, which is located approximately 124 light-years from Earth and orbits an M-dwarf star, which is smaller and cooler than our Sun. Previous studies suggested that K2-18 b could contain carbon dioxide, methane, and dimethyl sulfide (DMS), the last of which is produced by marine plankton on Earth. However, this most recent study used more in-depth data analysis techniques that confirmed the existence of methane while not finding evidence for the existence of carbon dioxide or DMS, which questions K2-18 b’s “hycean” classification.
The study notes, “Future JWST observations of sub-Neptunes will have a valuable role to play in assessing the existence of hycean worlds. Our results provide a cautionary tale for the value of exploring a spread of data-level and model-level approaches when retrieving sub-Neptune transmission spectra, with the consequence that there is currently no spectroscopic evidence for the existence of hycean planets in nature.”
This study comes as the number of confirmed exoplanets by NASA recently exceeded 6,000 with just over 25 percent being super-Earths, and sub-Neptunes being between the size of Earth and Neptune. Therefore, studies like this demonstrate the unique and wonderful aspects of exoplanets and where astronomers could search for life beyond Earth.
What new insight about K2-18 b and other sub-Neptunes will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Sources: The Astronomical Journal, NASA, NASA (1)
Featured Image Illustration Credit: NASA, ESA, CSA, Joseph Olmsted (STScI)