Self-consistent-field method for triaxial differentiated bodies in hydrostatic equilibrium

¹ Université Paris Cité, CNRS, Institut de Physique du Globe de Paris, 75005 Paris, France
² Université de Bordeaux, CNRS, Laboratoire d’Astrophysique de Bordeaux, 33615 Pessac, France

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 16 January 2026
Accepted: 10 March 2026

Abstract

Recent observations and models of Haumea and Quaoar suggest that both bodies are triaxial, but their shapes are inconsistent with Jacobi ellipsoids. To determine whether these objects can be at hydrostatic equilibrium, we propose a new numerical code, BALEINES, to study the hydrostatic shape of triaxial differentiated bodies. The fluid mass is assumed to be made of several homogeneous layers, which allowed us to rewrite the gravitational potential as a sum of proper surface integrals. In contrast to the classical self-consistent field method, we did not solve for the mass density, but for the shape of the boundary of all layers, meaning that only one point per layer is needed in the radial direction. The solution is still searched for iteratively. The code was benchmarked against analytical and numerical solutions. As a quick application, we studied the position of the axisymmetric-triaxial bifurcation point of two-layer systems. We show that the deviation from the Meyer bifurcation point in the single-layer case is below 10% in realistic cases. Based on this result, we conclude that the shape of Quaoar, as obtained in a recent work using a thermophysical model of the surface, is not compatible with a hydrostatic figure of equilibrium.