Overlaid rose diagram of the cluster (Gulliver 20). There are three different rose diagrams (see Sect. 2.1 for more details about constructing them) on the projection planes in the heliocentric Cartesian coordinate system before overlaying, with the X–Y plane (green), X–Z plane (pink), and Y–Z plane (blue). The circle region in dark purple represents the circle core of the cluster in a layered structure, while the region in dark blue represents its irregular core.