On The Capture of Interstellar Objects By Our Solar System


Examples of capture events. In each frame, the dotted black line denotes the rock’s initial (unbound) orbit; the solid black line denotes the rock’s trajectory after a perturbation; and the arrows specify the direction of the orbit. The yellow circle represents the Sun, the filled red circle represents Jupiter’s sphere of influence drawn at the epoch of the rock’s closest approach, and the red line marks Jupiter’s orbit. The top row shows a capture by Jupiter: the left panel is in the frame of the solar system’s barycenter, and the right panel is in Jupiter’s rest frame. Note that the rock gets well inside of Jupiter’s sphere of influence, but does not actually collide with the planet. The bottom row shows a capture by the Sun: the left panel is in the frame of the solar system’s barycenter, and the right panel is in the Sun’s rest frame. If the target (Sun or planet) has a component U of its velocity moving away from the incoming rock as it approaches periapsis, then the encounter causes the rock to lose energy in the inertial reference frame, thereby allowing the rock to potentially enter into a bound orbit.

Motivated by recent visits from interstellar comets, along with continuing discoveries of minor bodies in orbit of the Sun, this paper studies the capture of objects on initially hyperbolic orbits by our solar system.

Using an ensemble of ∼500 million numerical experiments, this work generalizes previous treatments by calculating the capture cross section as a function of asymptotic speed. The resulting velocity-dependent cross section can then be convolved with any distribution of relative speeds to determine the capture rate for incoming bodies.

This convolution is carried out for the usual Maxwellian distribution, as well as the velocity distribution expected for rocky debris ejected from planetary systems. We also construct an analytic description of the capture process that provides an explanation for the functional form of the capture cross section in both the high velocity and low velocity limits.

K. J. Napier, F. C. Adams, K. Batygin

Comments: 18 pages, 5 figures. Accepted to the Planetary Science Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2102.08488 [astro-ph.EP] (or arXiv:2102.08488v1 [astro-ph.EP] for this version)
Submission history
From: Kevin Napier
[v1] Tue, 16 Feb 2021 23:06:29 UTC (1,431 KB)
https://arxiv.org/abs/2102.08488

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