The Gateway Centaur and Jupiter co-orbital P/2019 LD2 (ATLAS) provides the first opportunity to observe the migration of a solar system small body from a Centaur orbit to a Jupiter Family Comet (JFC) four decades from now. The Gateway transition region is beyond where water ice can power cometary activity, and coma production there is as poorly understood as in all Centaurs. We present contemporaneous multiwavelength observations of LD2 from 2020 July 2–4: Gemini North visible imaging, NASA IRTF near-infrared spectroscopy, and ARO Submillimeter Telescope millimeter-wavelength spectroscopy. Precovery DECam images limit the nucleus’s effective radius to ≤1.2 km and no large outbursts were seen in archival Catalina Sky Survey observations. LD2's coma has , , a dust-production rate of ∼10–20 kg s⁻¹, and an outflow velocity between v ∼ 0.6–3.3 m s⁻¹. We did not detect CO toward LD2 on 2020 July 2–3, with a 3σ upper limit of Q(CO) < 4.4 10²⁷ mol s⁻¹ (⪅ 200 kg s⁻¹). Near-infrared spectra show evidence for water ice at the 1%–10% level depending on grain size. Spatial profiles and archival data are consistent with sustained activity. The evidence supports the hypothesis that LD2 is a typical small Centaur that will become a typical JFC, and thus, it is critical to understanding the transition between these two populations. Finally, we discuss potential strategies for a community-wide, long-baseline monitoring effort.

门户半人马座和木星同轨道P / 2019 LD2（ATLAS）提供了第一个机会来观察太阳系小天体从半人马座轨道到木星家庭彗星（JFC）的迁移，该过程已经持续了40年。盖特韦过渡地区不止于水冰可以推动彗星活动，那里的昏迷产生与所有半人马一样鲜为人知。我们介绍了从2020年7月2-4日起对LD2进行的同时多波长观测：双子座北可见成像，NASA IRTF近红外光谱和ARO亚毫米望远镜毫米波光谱。原始的DECam影像将原子核的有效半径限制为≤1.2km，并且在档案Catalina Sky Survey观测中没有看到大的爆发。LD2的昏迷了，，的无尘生产速度~10-20公斤小号^-1和之间的流出速度v〜0.6-3.3毫秒^-1。我们没有7月2日至3日在2020检测CO朝向LD2，用3 σ的上限Q（CO）<4.4 10 ²⁷摩尔小号^-1（⪅200公斤小号^-1）。近红外光谱表明，根据颗粒大小，水冰含量为1％–10％的证据。空间概况和档案数据与持续活动一致。证据支持以下假设：LD2是典型的小半人马，它将成为典型的JFC，因此，了解这两个种群之间的过渡至关重要。最后，我们讨论了在整个社区范围内进行长期基线监测的潜在策略。