The origin of (47171) Lempo-like Kuiper belt triple systems during binary-binary interactions
Abstract
The trans-Neptunian triple Lempo-Paha-Hiisi is composed of a tight inner binary with components of similar size and an outer companion about half their size orbiting 10 times further away. Large trans-Neptunian objects like Pluto also have multiple small moons, but Lempo's structure is unique in the Solar system, and the place and timing of its origin is still a subject of debate. We propose a new formation mechanism able to form a large number of systems like Lempo-Paha-Hiisi, which involves binary-binary close encounters in the primordial planetesimal disc at 30-40 au. Some of these systems were then implanted in different populations of the trans-Neptunian region during Neptune's outward migration. Our results strongly support that the 4:7 resonant multiple object Manwë-Thorondor was once a triple system similar to Lempo-Paha-Hiisi, but the orbit of the inner binary evolved by tides, becoming a contact binary. As with Lempo-Paha-Hiisi, it should have originated in the planetesimal disc below 30-40 au. Triple systems like Lempo-Paha-Hiisi or Manwë-Thorondor could not have formed in situ and the existence of this kind of system is not expected in the cold classical Kuiper belt.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2020
- DOI:
- 10.1093/mnras/staa3105
- Bibcode:
- 2020MNRAS.499.4206B
- Keywords:
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- Kuiper belt: general;
- Kuiper belt objects: individual: Lempo-Paha-Hiisi;
- Comets: general