1I/‘Oumuamua as an N₂ Ice Fragment of an Exo-Pluto Surface II: Generation of N₂ Ice Fragments and the Origin of ‘Oumuamua

The origin of the interstellar object 1I/‘Oumuamua has defied explanation. In a companion paper (Jackson & Desch, 2021), we show that a body of N₂ ice with axes 45 m × 44 m × 7.5 m at the time of observation would be consistent with its albedo, nongravitational acceleration, and lack of observed CO or CO₂ or dust. Here we demonstrate that impacts on the surfaces of Pluto-like Kuiper belt objects (KBOs) would have generated and ejected ∼10¹⁴ collisional fragments—roughly half of them H₂O ice fragments and half of them N₂ ice fragments—due to the dynamical instability that depleted the primordial Kuiper belt. We show consistency between these numbers and the frequency with which we would observe interstellar objects like 1I/‘Oumuamua, and more comet-like objects like 2I/Borisov, if other stellar systems eject such objects with efficiency like that of the Sun; we infer that differentiated KBOs and dynamical instabilities that eject impact-generated fragments may be near-universal among extrasolar systems. Galactic cosmic rays would erode such fragments over 4.5 Gyr, so that fragments are a small fraction (∼0.1%) of long-period Oort comets, but C/2016 R2 may be an example. We estimate ‘Oumuamua was ejected about 0.4–0.5 Gyr ago, from a young (∼10⁸ yr) stellar system, which we speculate was in the Perseus arm. Objects like ‘Oumuamua may directly probe the surface compositions of a hitherto-unobserved type of exoplanet: “exo-Plutos.” ‘Oumuamua may be the first sample of an exoplanet brought to us.