Gas Giant
Image from Steve Bowers

Also known as Jovian Class. Gas Giants can be classified by mass, into MicroJovian, SubJovian, MesoJovian, and SuperJovian types; they can also be classified by temperature, into HyperthermalJovian, EpistellarJovian, HydroJovian, EuJovian and CryoJovian types. A particular gas giant can be classified using both criteria, for example CryoMesoJovian type or SubEuJovian type.


Gas giants often rotate very rapidly, and this rotation causes them to become oblate. The degree of oblateness is dependent on the both the speed of rotation and the surface gravity, so that the most oblate gas giants are those with relatively low gravity and fast rotation.


Behemoth Hat-p-1b
Image from Steve Bowers
Behemoth, a Hyperthermal Jovian, compared in size to Jupiter.
The largest known gas giants are members of the HyperthermalJovian type, since their high temperature causes them to become less dense and this reduces their surface gravity. Cooler gas giants with the same mass are generally smaller, and due to compression they are rarely much larger than Jupiter. The least dense cool giants have very small rocky cores, a subtype that is quite rare - most of these giants are very old, and have lost nearly all the heat of formation that younger examples retain.


Most gas giants have some sort of ring system, although in many cases these rings are almost invisible. Some giants have spectacular rings, often striated due to tidal interactions with the moons of that world.

Image from Steve Bowers
Menexenos in the Socrates 471 system
Canaria ::
Canaria in the Guanche system
Image from Steve Bowers
Hibou in the Calyx system
Hati in the Proxima System
Image from Steve Bowers
Franklin in the Beta Virginis system
Image from Steve Bowers
Saturn in the Solsys system
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Development Notes
Text by M. Alan Kazlev
Additional material by Steve Bowers (2018)
Initially published on 09 December 2001.