The Jovian-sized object WD1856b transits a white dwarf (WD) in a compact 1.4 day orbit. Unlikely to have endured stellar evolution in its current orbit, WD1856b is thought to have migrated from much wider separations. Because the WD is old, and a member of a well-characterized hierarchical multiple, the well-known Kozai mechanism provides an effective migration channel for WD1856b. The tidal dissipation that makes this mechanism possible is sensitive to the mass of WD1856b, which remains unconstrained by observations. Moreover, the lack of tides in the star allows us to directly connect the current semimajor axis to the pre-migration one, from which we can infer the initial conditions of the system. By further requiring that planets must survive all previous phases of stellar evolution before migrating, we are able to constrain the main-sequence semimajor axis of WD1856b to have been ∼2.5 au, and its mass to be ≃0.7–3M _J. These mass limits put WD1856b firmly within the planet category. Furthermore, our inferred values imply that WD1856b was born a typical gas giant. We further estimate the occurrence rate of Kozai-migrated planets around WDs to be , suggesting that WD1856b is the only one in the TESS sample, but implying future detections by the LSST survey. In a sense, WD1856b was an ordinary Jovian planet that underwent an extraordinary dynamical history.

木星大小的天体 WD1856b 在紧凑的 1.4 天轨道上经过白矮星 (WD)。WD1856b 不太可能在其当前轨道上经历恒星演化，被认为是从更广泛的分离中迁移出来的。由于 WD 是旧的，并且是特征良好的分层多级的成员，众所周知的 Kozai 机制为 WD1856b 提供了有效的迁移通道。使这种机制成为可能的潮汐耗散对 WD1856b 的质量很敏感，它不受观测的约束。此外，恒星中没有潮汐使我们能够将当前的半长轴直接连接到迁移前的半轴，从中我们可以推断出系统的初始条件。通过进一步要求行星在迁移之前必须在恒星演化的所有先前阶段中幸存下来，米杰 。_{_} 这些质量限制使 WD1856b 牢牢地属于行星类别。此外，我们的推断值暗示 WD1856b 天生就是一颗典型的气态巨行星。我们进一步估计 WD 周围的 Kozai 迁移行星的发生率是，这表明 WD1856b 是 TESS 样本中唯一的一颗，但暗示未来将通过 LSST 调查发现。从某种意义上说，WD1856b是一颗普通的木星行星，经历了一段非凡的动力学历史。