hycean

With densities between those of rocky super-Earths and more extended mini-Neptunes, Hycean planets can be optimal candidates in the search for exoplanetary habitability and may be abundant in the exoplanet population.

2021 August, Nikku Madhusudhan, Anjali A. A. Piette, Savvas Constantinou, “Habitability and Biosignatures of Hycean Worlds”, in Astrophysical Journal

It's thought that the new classification could accelerate the search for life outside our Solar System for one simple reason: planets that fulfil the criteria to be "Hycean" already dominate the known exoplanet population, which is approaching 4,500.

2021 August 25, Jamie Carter, “Is Alien Life Hiding In Plain Sight? New Class Of 'Hycean' Planet Is Where We Should Look, Say Scientists”, in Forbes

And learning more about Hycean planets could help scientists find biosignatures, or signs of life, outside of our solar system in the near future.

2021 August 26, Ashley Strickland, CNN

TOI-2136b is a sub-Neptune transiting a nearby and bright star (J=10.8) and is a potential hycean planet, making it an excellent target for atmospheric studies to understand the formation, evolution, and habitability of the small planets.

2022 February 21, K Kawauchi, F Murgas, E Palle, N Narita, A Fukui, et al., “Validation and atmospheric exploration of the sub-Neptune TOI-2136b around a nearby M3 dwarf”, in arXiv.org, →DOI

While LTT 1445 Ab is not in the traditional habitable zone of its star (Winters et al. 2019), it is considered as a candidate Hycean world where a liquid ocean may exist underneath a H₂-dominated atmosphere.

2022 September 26, Caprice Phillips, Ji Wang, Billy Edwards, Romy Rodriguez Martinez, Anusha Pai Asnodkar, B. Scott Gaudi, “Is LTT 1445 Ab a Hycean World or a cold Haber World? Exploring the Potential of Twinkle to Unveil Its Nature”, in arXiv, →DOI