The solar system’s distant reaches exhibit a wealth of anomalous dynamical structure, hinting at the presence of a yet-undetected, massive trans-Neptunian body—Planet Nine (P9). Previous analyses have shown how orbital evolution induced by this object can explain the origins of a broad assortment of exotic orbits, ranging from those characterized by high perihelia to those with extreme inclinations. In this work, we shift the focus toward a more conventional class of TNOs and consider the observed census of long-period, nearly planar, Neptune-crossing objects as a hitherto-unexplored probe of the P9 hypothesis. To this end, we carry out comprehensive N-body simulations that self-consistently model gravitational perturbations from all giant planets, the Galactic tide, as well as passing stars, stemming from initial conditions that account for the primordial giant planet migration and Sun's early evolution within a star cluster. Accounting for observational biases, our results reveal that the orbital architecture of this group of objects aligns closely with the predictions of the P9-inclusive model. In stark contrast, the P9-free scenario is statistically rejected at a ∼5σ confidence level. Accordingly, this work introduces a new line of evidence supporting the existence of P9 and further delineates a series of observational predictions poised for near-term resolution.

中文翻译：

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九号行星产生低倾角、穿过海王星的海王星天体

太阳系的遥远区域展现出丰富的异常动力结构，暗示存在尚未被发现的巨大海王星外天体——第九行星（P9）。先前的分析表明，该天体引起的轨道演化如何解释各种奇异轨道的起源，从具有高近日点特征的轨道到具有极端倾角的轨道。在这项工作中，我们将焦点转向更传统的海王星天体类别，并将观测到的长周期、近平面、穿越海王星天体的普查视为迄今为止尚未探索的 P9 假说探索。为此，我们全面开展氮- 体模拟，自洽地模拟来自所有巨行星、银河潮汐以及经过的恒星的引力扰动，这些扰动源于解释原始巨行星迁移和太阳在星团内早期演化的初始条件。考虑到观测偏差，我们的结果表明这组天体的轨道结构与包含 P9 的模型的预测密切相关。形成鲜明对比的是，无 P9 的场景在统计学上被拒绝为 ∼5σ置信水平。因此，这项工作引入了支持 P9 存在的新证据，并进一步描绘了一系列有望在近期得到解决的观测预测。