Best-fit orbit in a simple model for the gravitational potential of the Milky Way using Gaia proper motions and the filtered stream track. The left panel shows the orbit in Galactocentric cylindrical radius, R, and position above the Galactic midplane, z; the gray line at z = 0 shows the approximate radius of the disk. The right panel shows the orbit projected onto the midplane in Galactocentric cartesian coordinates, (x, y). The darker orbit section highlights the stream longitudes over which we clearly see GD-1 stream stars. Note that GD-1 is retrograde with respect to the disk (location and direction of motion of the Sun are indicated in the right panel, ⊙).