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## The interstellar object 'Oumuamua as a fractal dust aggregate

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Eirik G. Flekkøy
• Function : Author
Renaud Toussaint

#### 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.

### Dates and versions

insu-02348185 , version 1 (05-11-2019)

### Identifiers

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

### Cite

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

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