insu-02348185
https://insu.hal.science/insu-02348185
arxiv:1910.07135
[INSU] INSU - Institut National des Sciences de l'Univers
[CNRS] CNRS - Centre national de la recherche scientifique
[UNIV-STRASBG] Université de Strasbourg
[SITE-ALSACE] Archive ouverte du site Alsace
The interstellar object 'Oumuamua as a fractal dust aggregate
Flekkøy, Eirik G.
Luu, Jane X.
Toussaint, Renaud
[PHYS.ASTR.EP] Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
[PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph]
UNDEFINED
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.
2019-11-05
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