We fit an isothermal oscillatory density model of Neptune ’ s protoplanetary disk to the surviving regular satellites and its innermost ring and we determine the radial scale length of the disk , the equation of state and the central density of the primordial gas , and the rotational state of the Neptunian nebula .
Neptune ’ s regular moons suffered from the retrograde capture of Triton that disrupted the system .
Some moons may have been ejected , while others may have survived inside their potential minima .
For this reason , the Neptunian nebula does not look like any of the nebulae that we modeled previously .
In particular , there must be two density maxima deep inside the core of the nebula where no moons or rings are found nowadays .
Even with this strong assumption , the recent discovery of the minor moon N XIV complicates further the modeling effort .
With some additional assumptions , the Neptunian nebula still shares many similarities with the Uranian nebula , as was expected from the relative proximity and similar physical conditions of the two systems .
For Neptune ’ s primordial disk , we find a steep power-law index ( k = -3.0 ) , needed to accommodate the arrangement of the outer moons Larissa , N XIV , and Proteus .
The rotation parameter that measures centrifugal support against self-gravity is quite small ( \beta _ { 0 } = 0.00808 ) , as is its radial scale length ( 13.6 km ) .
The extent of the disk ( R _ { max } = 0.12 Gm ) is a lot smaller than that of Uranus ( R _ { max } = 0.60 Gm ) and Triton appears to be responsible for the truncation of the disk .
The central density of the compact Neptunian core and its angular velocity are higher than but comparable to those of Uranus ’ core .
In the end , we compare the models of the protoplanetary disks of the four gaseous giants .