On-sky positions of likely GD-1 members in the GD-1 coordinate system. GD-1 is apparent as an overdensity in negative proper motions (top-right panel, orange box), so selecting on proper motion already reveals the stream in positions of individual stars (top-left panel). The stream also stands out in the color–magnitude diagram (bottom-right panel) as older and more metal-poor than the background. Selecting the main sequence of GD-1 (orange, shaded region in the bottom-right panel) along with proper motion cuts unveils the stream in unprecedented detail (bottom-left panel).