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Haumea's Shape and Composition

Status Report From: arXiv.org e-Print archive
Posted: Monday, April 1, 2019

Emilie T. Dunham, Steven J. Desch, Luke Probst

(Submitted on 1 Apr 2019)

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 Haumea is a uniform triaxial ellipsoid consistent with a Jacobi ellipsoid with axes ≈960×774×513 km, and bulk density ≈2600kgm−3. In contrast, observations of a recent stellar occultation by Haumea indicate its axes are ≈1161×852×523 km and its bulk density ≈1885kgm−3; these results suggest that Haumea cannot be a fluid in hydrostatic equilibrium and must be partially supported by interparticle forces. We have written a code to reconcile these contradictory results and to determine if 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 (semi-) axes lengths a and b. We find 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 ρavg=2018kgm−3, ρcore=2680kgm−3, and core axes ac=883 km, bc=723 km, and cc=470 km, which equates to an ice mantle comprising ∼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.

Comments: 15 pages, 3 figures, accepted for publication in ApJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:1904.00522 [astro-ph.EP] (or arXiv:1904.00522v1 [astro-ph.EP] for this version)

Submission history

From: Emilie Dunham

[v1] Mon, 1 Apr 2019 01:04:32 UTC (3,356 KB)

https://arxiv.org/abs/1904.00522

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