BY LETTER
Psychronian
Cold giant planets | |
 Image from Steve Bowers | |
| Jupiter, a Psychronian Jovian in Solsys | |
In NoLWoCS, Psychronians (prefix: Psychro-; eg. PsychroNeptunian, PsychroJovian) are cold giant planets, with tropopause temperatures between 70 K, below which methane absorption dominates and the planet becomes a Cryonian, and 200 K, above which water clouds dominate and the planet becomes a Mesonian. Psychronians are characterized by the presence of clouds of ammonium hydrosulfide (NH4SH) and ammonia (NH3), which give them a white colour. On Psychronians receiving sufficient high energy radiation, photochemical haze forms as ammonia, acetylene, and methane react with each other, producing a beige tint.
Psychronians often feature numerous bands and storms with lighter and darker colours, resulting from local variations in density of photochemical haze and opacity of clouds, as well as the vertical extent of these components. Notably, regions shaded from sunlight develop a blueish tint, as the lack of haze production reduced the beige tinting, and the cooling of the atmosphere caused white clouds to sink deeper, enabling methane absorption to dominate. Additionally, haze can be temporarily cleared by certain types of storms, also resulting in blueish regions.
Psychronians can be found in a wide range of masses, from neptunians to some less massive superjovians; worlds more massive than several Jupiter masses have not had enough time to cool down sufficiently from formation. Owing to their common formation location near the water frost line coinciding with a distance suitable for this temperature type, as well as their internal heat flux, most jovian planets are either Psychronians or Mesonians.
Images of Psychronian worlds
 Image from Steve Bowers | |
| Zeus | |
 Image from Steve Bowers | |
| Natasha (Zeta1 Reticuli system) | |
 Image from Steve Bowers | |
| Saturn (with its moon Titan in the foreground) | |
 Image from Steve Bowers | |
| Iberer, with irregular rings following a near encounter with a rogue planet | |
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Development Notes
Text by AstroChara
John M. Dollan in his Planet Classification List
Initially published on 24 October 2001.
Overhauled 2025-10-14 by AstroChara
John M. Dollan in his Planet Classification List
Initially published on 24 October 2001.
Overhauled 2025-10-14 by AstroChara
