TY - JOUR
T1 - 1I/‘Oumuamua as an N2 Ice Fragment of an Exo-Pluto Surface II
T2 - Generation of N2 Ice Fragments and the Origin of ‘Oumuamua
AU - Desch, S. J.
AU - Jackson, A. P.
N1 - Funding Information:
We thank Yusuke Fujimoto, Chris Glein, Greg Laughlin, and Darryl Seligman for useful discussions. We thank an anonymous referee and especially the referee Sean Raymond for comments that helped us improve the clarity of the manuscript. The results reported herein benefitted from collaborations and/or information exchange within NASA's Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA's Science Mission Directorate.
Publisher Copyright:
© 2021. The Authors.
PY - 2021/5
Y1 - 2021/5
N2 - 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.
AB - 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.
KW - 'Oumuamua
KW - Kuiper Belt
KW - Pluto
KW - exoplanets
UR - http://www.scopus.com/inward/record.url?scp=85106962303&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85106962303&partnerID=8YFLogxK
U2 - 10.1029/2020JE006807
DO - 10.1029/2020JE006807
M3 - Article
AN - SCOPUS:85106962303
VL - 126
JO - Journal of Geophysical Research: Planets
JF - Journal of Geophysical Research: Planets
SN - 2169-9097
IS - 5
M1 - e2020JE006807
ER -