The origin of the interstellar object 1I/‘Oumuamua has defied explanation. We perform calculations of the non‐gravitational acceleration that would be experienced by bodies composed of a range of different ices and demonstrate that a body composed of N₂ ice would satisfy the available constraints on the non‐gravitational acceleration, size, and albedo, and lack of detectable emission of CO or CO₂ or dust. We find that ‘Oumuamua was small, with dimensions 45 m × 44 m × 7.5 m at the time of observation at 1.42 au from the Sun, with a high albedo of 0.64. This albedo is consistent with the N₂ surfaces of bodies like Pluto and Triton. We estimate ‘Oumuamua was ejected about 0.4–0.5 Gyr ago from a young stellar system, possibly in the Perseus arm. Objects like ‘Oumuamua may directly probe the surface compositions of a hitherto‐unobserved type of exoplanet: “exo‐plutos”. In a companion paper (Desch & Jackson, 2021) we demonstrate that dynamical instabilities like the one experienced by the Kuiper belt, in other stellar systems, plausibly could generate and eject large numbers of N₂ ice fragments. ‘Oumuamua may be the first sample of an exoplanet brought to us.

中文翻译：

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1I /'Oumuamua作为外冥王星表面的N2冰碎片：I.大小和组成约束

星际物体1I /'Oumuamua的起源已被拒绝解释。我们对由一系列不同的冰组成的物体将经历的非重力加速度进行计算，并证明由N ₂冰组成的物体将满足对非重力加速度，大小和反照率的可用约束，并且缺乏可检测到的CO或CO ₂或粉尘排放。我们发现，'Oumuamua很小，在距太阳1.42 au处观察时尺寸为45 m×44 m×7.5 m，反照率很高，为0.64。这个反照率与N ₂相一致冥王星和海卫一等物体的表面。我们估计'Oumuamua大约在0.4-0.5 Gyr之前从一个年轻的恒星系统中弹出，可能是在英仙座臂中弹出的。诸如“ Oumuamua”之类的物体可以直接探测迄今未观察到的系外行星：“ exo-plutos”的表面成分。在另一篇论文中（Desch＆Jackson，2021年），我们证明了动力学不稳定性，如柯伊伯带所经历的动力学不稳定性，在其他恒星系统中，可能会产生并喷射出大量的N ₂冰碎片。“ Oumuamua可能是带给我们的系外行星的第一个样本。