Formation of moons and equatorial ridge around top-shaped asteroids after surface landslide
| Autor: | Hyodo, Ryuki, Sugiura, Keisuke |
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| Rok vydání: | 2022 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.3847/2041-8213/ac922d |
| Popis: | Top-shaped asteroids have been observed among near-Earth asteroids. About half of them are reported to have moons (on the order of $\sim 1$wt.\% of the top-shaped primary) and many of them have an equatorial ridge. A recent study has shown that the enigmatic top-shaped figure of asteroids (e.g., Ryugu, Bennu, and Didymos) could result from an axisymmetric landslide of the primary during a fast spin-up near the breakup rotation period. Such a landslide would inevitably form a particulate disk around an asteroid with a short timescale ($\sim 3$ hours). However, the long-term full dynamical evolution is not investigated. Here, we perform a continuous simulation ($\sim 700$ hours) that investigates the sequence of events from the surface landslide that forms a top-shaped asteroid and a particulate disk to disk evolution. We show that the disk quickly spreads and produces moons (within $\sim 300$ hours). The mass of the formed moon is consistent with what is observed around the top-shaped asteroids. We also demonstrate that an equatorial ridge is naturally formed because a fraction of the disk particles re-accretes selectively onto the equatorial region of the primary. We envision that Ryugu and Bennu could once have an ancient moon that was later lost due to a successive moon's orbital evolution. Alternatively, at the top-shaped asteroid that has a moon, such as Didymos, no significant orbital evolution of the moon has occurred that would result in its loss. Our study would also be qualitatively applicable to any rubble-pile asteroids near the breakup rotation period. Comment: 8 pages, 5 Figures, accepted for publication in ApJL (Astrophysical Journal Letters) |
| Databáze: | arXiv |
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