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# The interstellar object 'Oumuamua as a fractal dust aggregate

1 PoreLab [Oslo]
Department of Physics [Oslo], NTNU - Norwegian University of Science and Technology [Oslo]
Abstract : The first known interstellar object 'Oumuamua exhibited a nongravitational acceleration that appeared inconsistent with cometary outgassing, leaving radiation pressure as the most likely force. Bar the alien lightsail hypothesis, an ultra-low density due to a fractal structure might also explain the acceleration of 'Oumuamua by radiation pressure (Moro-Martin 2019). In this paper we report a decrease in 'Oumuamua's rotation period based on ground-based observations, and show that this spin-down can be explained by the YORP effect if 'Oumuamua is indeed a fractal body with the ultra-low density of $10^{-2}$ kg m$^{-3}$. We also investigate the mechanical consequences of 'Oumuamua as a fractal body subjected to rotational and tidal forces, and show that a fractal structure can survive these mechanical forces.
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Preprints, Working Papers, ...
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https://hal-insu.archives-ouvertes.fr/insu-02348185
Contributor : Renaud Toussaint <>
Submitted on : Tuesday, November 5, 2019 - 12:46:25 PM
Last modification on : Monday, March 9, 2020 - 3:54:02 PM

### Identifiers

• HAL Id : insu-02348185, version 1
• ARXIV : 1910.07135

### Citation

Eirik G. Flekkøy, Jane X. Luu, Renaud Toussaint. The interstellar object 'Oumuamua as a fractal dust aggregate. 2019. ⟨insu-02348185⟩

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