Haumea's Shape, Composition, and Internal Structure

E. T. Dunham, Steven Desch, L. Probst

Research output: Contribution to journalArticle

Abstract

We have calculated the figure of equilibrium of a rapidly rotating, differentiated body to determine the shape, structure, and composition of the dwarf planet Haumea. Previous studies of Haumea's light curve have suggested that Haumea is a uniform triaxial ellipsoid consistent with a Jacobi ellipsoid with axes ≈960 × 774 × 513 km and bulk density ≈2600 kg m-3. In contrast, observations of a recent occultation of Haumea indicate that its axes are ≈1161 × 852 × 523 km and its bulk density is ≈1885 kg m-3; these results suggest that Haumea cannot be a fluid in hydrostatic equilibrium and must be supported by interparticle forces. We have written a code to reconcile these contradictory results and to determine whether Haumea is in fact a fluid in hydrostatic equilibrium. The code calculates the equilibrium shape, density, and ice crust thickness of a differentiated Haumea after imposing axis lengths a and b. We find that Haumea is consistent with a differentiated triaxial ellipsoid fluid in hydrostatic equilibrium with axes of best fit a = 1050 km, b = 840 km, and c = 537 km. This solution for Haumea has ρ avg = 2018 kg m-3, ρ core = 2680 kg m-3, and core axes a c = 883 km, b c = 723 km, and c c = 470 km, which equates to an ice mantle composing ∼17% of Haumea's volume and ranging from 67 to 167 km in thickness. The thick ice crust we infer allows for Haumea's collisional family to represent only a small fraction of Haumea's pre-collisional ice crust. For a wide range of parameters, the core density we calculate for Haumea suggests that today the core is composed of hydrated silicates and likely underwent serpentinization in the past.

Original languageEnglish (US)
Article number41
JournalAstrophysical Journal
Volume877
Issue number1
DOIs
StatePublished - May 20 2019

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ice
ellipsoids
hydrostatics
crusts
crust
bulk density
fluid
fluids
dwarf planets
rotating bodies
serpentinization
occultation
light curve
silicates
Earth mantle
planet
silicate
mantle
code

Keywords

  • Kuiper belt objects: individual (Haumea)
  • planets and satellites: composition
  • planets and satellites: formation
  • planets and satellites: interiors

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Haumea's Shape, Composition, and Internal Structure. / Dunham, E. T.; Desch, Steven; Probst, L.

In: Astrophysical Journal, Vol. 877, No. 1, 41, 20.05.2019.

Research output: Contribution to journalArticle

Dunham, E. T. ; Desch, Steven ; Probst, L. / Haumea's Shape, Composition, and Internal Structure. In: Astrophysical Journal. 2019 ; Vol. 877, No. 1.
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