%0 Unpublished work
%T The interstellar object 'Oumuamua as a fractal dust aggregate
%+ PoreLab [Oslo]
%+ Centre for Earth Evolution and Dynamics [Oslo] (CEED)
%+ Institute of Theoretical Astrophysics [Oslo]
%+ Institut de physique du globe de Strasbourg (IPGS)
%A Flekkøy, Eirik G.
%A Luu, Jane X.
%A Toussaint, Renaud
%Z Astrophysical Journal Letters, accepted, in press - 8 pages, 3 figures
%8 2019-11-05
%D 2019
%Z 1910.07135
%Z Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
%Z Physics [physics]/Astrophysics [astro-ph]Preprints, Working Papers, ...
%X 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.
%G English
%L insu-02348185
%U https://insu.hal.science/insu-02348185
%~ INSU
%~ CNRS
%~ UNIV-STRASBG
%~ SITE-ALSACE