Octahedral gravity – the case of asteroid (162173) Ryugu

animates_octahedron
Gravitational potential of an octahedron (rough estimate: 1.4 km diameter, density 1500 kg/m3), with added centrifugal term (7 h rotation). Credit: Tobias Kramer, 2018
fig_hayabusa2_ryugu
Asteroid Ryugu (June 24, 2018). Credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, Aizu University, AIST

Asteroid Ryugu

The Hayabusa 2 target asteroid (162173) Ryugu displays a strange diamond like shape, at least from the sunny side explored so far.
Time for me to reuse the code developed for comet 67P/Churyumov-Gerasimenko and to compute the gravitational potential (with added centrifugal term, assuming a 7 h rotation period). The rotation weakens the gravitational potential in the equator regions. Otherwise on the triangular faces the potential minima are close to the centers of the triangle.

Update: new JAXA images, an animation of the rotation, and a shape model extracted by Doug Ellison. This allows me to recompute the effective gravitational potential (assuming a uniform density):

ryugo_gravity

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