An “approximately” true color image of Ceres taken by the Dawn spacecraft as it approached the dwarf planet in May, 2015. (credit: NASA)
A team of researchers has used data from the Dawn spacecraft to piece together clues about the interior of the dwarf planet Ceres. The new data indicates that while Ceres, which is the largest body in the asteroid belt, was once warm enough for water to have shifted internally, those temperatures were never high enough for an iron core to separate from the rest of the dwarf planet’s interior.
Measuring gravity
The new information comes in part from an estimate of Ceres’ moment of inertia, a measure of a body’s resistance to being spun on its axis. A body’s moment of inertia depends on two factors. First is the variation of its gravity field over its surface: even though Ceres is roughly spherical, its gravitational strength isn’t uniform. These variations can’t be measured from Earth, though.
The second factor is whether Ceres’ gravity is strong enough to collapse it into a roughly spherical shape, bringing the internal forces into balance with each other. This state is called hydrostatic equilibrium, and it can only be estimated if researchers can determine Ceres’ precise precession rate, which is too small to observe from Earth.
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Source: Ars Technica – Dawn glimpses Ceres’ internal structure