英和和英

語源

Blend of hydrogen +‎ ocean. Coined in 2021.

発音

• IPA: /ˈhaɪʃən/

形容詞

hycean (not comparable)

1. (astronomy, planetology, of a planet, neologism) Having a water-based ocean that covers the entire planet, and an atmosphere rich in hydrogen.
   • 2021 August, Nikku Madhusudhan, Anjali A. A. Piette, Savvas Constantinou, “Habitability and Biosignatures of Hycean Worlds”, in Astrophysical Journal:

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

     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 26, Ashley Strickland, CNN:

     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 September 2, Joshua Colwell, Adrienne Dove, James Cooney, “Hycean Worlds and Nudging Asteroids”, in Walkabout the Galaxy:

     These hydrogen-rich ocean worlds, or hycean worlds, may be habitable.

   • 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:

     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 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:

     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.

使用する際の注意点

Sometimes unnecessarily capitalised, possibly reflecting a false assumption about the etymology.

参考

• ocean world

Further reading

• Ocean world on Wikipedia.Wikipedia

アナグラム

• Cheyna, Ceyhan, Chaney