In a cosmological setting, the disk of a galaxy is expected to continuously experience gravitational torques and perturbations from a variety of sources, which can cause the disk to wobble, flare and warp^1,2. Specifically, the study of galactic warps and their dynamic nature could reveal key information on the formation history of galaxies and the mass distribution of their haloes. Our Milky Way presents a unique case study for galactic warps, thanks to detailed knowledge of its stellar distribution and kinematics. Using a simple model of how the warp’s orientation is changing with time, here, we measure the precession rate of the Milky Way’s warp using 12 million giant stars from Gaia Data Release 2³, finding that it is precessing at 10.86 ± 0.03 (statistical) ± 3.20 (systematic) km s⁻¹ kpc⁻¹ in the direction of Galactic rotation, about one-third the angular rotation velocity at the Sun’s position in the Galaxy. The direction and magnitude of the warp’s precession rate favour the scenario that the warp is the result of a recent or ongoing encounter with a satellite galaxy, rather than the relic of the ancient assembly history of the Galaxy.

在宇宙学环境中，星系的圆盘预计会持续经历来自各种来源的引力扭矩和扰动，这可能导致圆盘摆动、耀斑和扭曲^1,2。具体而言，对星系扭曲及其动力学性质的研究可以揭示有关星系形成历史及其晕圈质量分布的关键信息。由于对其恒星分布和运动学的详细了解，我们的银河系为银河扭曲提供了一个独特的案例研究。^{使用一个关于曲速方向如何随时间变化的简单模型，在这里，我们使用来自 Gaia Data Release 2 3}的 1200 万颗巨星来测量银河系曲速的进动率，发现它在银河旋转方向上的进动速度为 10.86 ± 0.03（统计）± 3.20（系统）km s ^-1  kpc ^-1，大约是太阳在银河系中角旋转速度的三分之一。经线进动速率的方向和幅度有利于这样一种情况，即经线是最近或正在进行的与卫星星系相遇的结果，而不是银河系古代组装历史的遗迹。