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There has been an increasing amount of interest in the possibility of primordial black holes and that Planet Nine may be one itself. Planet Nine is a potential explanation for the orbital characteristics of various TNOs (trans-Neptunian object). I'm curious if it would be possible for our two interstellar visitors ('Oumuamua and Borisov) to be from this solar system but have been given a gravitational assist by a small black hole to provide them with their high eccentricity. I further wonder if the elongation of the low density 'Oumuamua could be due the effects of a close orbit around a small object of unusual large density.

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  • $\begingroup$ I think that the two objects are too fast to be from the Oort cloud, they've reached solar escape velocity. And Planet IX is even closer: at 1200 au farthest (aphelion) while the hypothetical Oort cloud begins at about 10000 au. We know when a comet hails from the Oort cloud but it may be that the two objects indeed hail from black holes or neutron stars or whatever. But that sounds like another good question. $\endgroup$ – Ioannes Jul 17 '20 at 6:21
  • $\begingroup$ Could an interaction with Planet IX after an established long-period orbit resolve your objection? $\endgroup$ – Matthew Armstrong Jul 17 '20 at 9:43
  • $\begingroup$ I think the two objects are too fast to have even a long-period orbit. They are at solar escape velocity, meaning they can't possibly be in an orbit around the Sun. They're "slingshooting" the Sun instead. Maybe their path was altered by some planet they approached, including the hypothetical ninth planet, but it's not a solar orbit. Also, an Oort cloud object is more likely to have done something to the objects' paths than Planet IX. Maybe Tyche, another hypothetical planet or brown dwarf. Tyche would be in the Oort cloud. $\endgroup$ – Ioannes Jul 17 '20 at 10:48
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    $\begingroup$ Also, the incoming trajectories originate in two very different directions. If a single object several hundred AU from the sun deflected both objects, it wouldn't have moved very far along its orbit between the two encounters, and both interstellar objects would have approached the sun from similar directions. $\endgroup$ – notovny Jul 17 '20 at 23:51
  • $\begingroup$ Let's assume both were travelling away from our solar system when they encountered a small black hole. Also, 'Oumuamua fell closer to it than Borisov. Given these assumptions and the observations made of these two objects, could we plot the probably location range for the black hole right now? Could we calculate the mass of the black hole based on the elongation of 'Oumuamua from a sphere? As a novice astronomer but able programmer where would I start to simulate this? Thanks! $\endgroup$ – Matthew Armstrong Jul 18 '20 at 19:53

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