Is there an exoplanet in the Solar system?
Abstract
We investigate the prospects for the capture of the proposed Planet 9 from other stars in the Sun's birth cluster. Any capture scenario must satisfy three conditions: the encounter must be more distant than ∼150 au to avoid perturbing the Kuiper belt; the other star must have a wide-orbit planet (a ≳ 100 au); the planet must be captured on to an appropriate orbit to sculpt the orbital distribution of wide-orbit Solar system bodies. Here we use N-body simulations to show that these criteria may be simultaneously satisfied. In a few per cent of slow close encounters in a cluster, bodies are captured on to heliocentric, Planet 9-like orbits. During the ∼100 Myr cluster phase, many stars are likely to host planets on highly eccentric orbits with apastron distances beyond 100 au if Neptune-sized planets are common and susceptible to planet-planet scattering. While the existence of Planet 9 remains unproven, we consider capture from one of the Sun's young brethren a plausible route to explain such an object's orbit. Capture appears to predict a large population of trans-Neptunian objects (TNOs) whose orbits are aligned with the captured planet, and we propose that different formation mechanisms will be distinguishable based on their imprint on the distribution of TNOs.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2016
- DOI:
- 10.1093/mnrasl/slw075
- arXiv:
- arXiv:1603.07247
- Bibcode:
- 2016MNRAS.460L.109M
- Keywords:
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- Kuiper belt: general;
- planets and satellites: dynamical evolution and stability;
- planets and satellites: individual: Planet 9;
- planetary systems;
- open clusters and associations: general;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 5 pages + appendix. Accepted to MNRAS Letters: replaced with accepted version