Orbital properties of HE2159-0551 (red star) compared to known stellar substructures in the Milky Way. Left: E–L_z diagram showing orbital energy vs. angular momentum. Colored points and contours (based on a Gaussian density distribution) indicate the location of accreted populations from the literature. Specifically, GES (Belokurov et al. 2018; Helmi et al. 2018), Sequoia (Myeong et al. 2019), Thamnos (Koppelman et al. 2019a), Helmi stream (Helmi et al. 1999), LMS-1 (Yuan et al. 2020), and Wukong (Naidu et al. 2020) are shown. HE2159-0551 lies within the Wukong selection region, but at the prograde edge of the structure. Right: action diamond diagram with x = J_ϕ/J_tot and y = (J_z – J_R)/J_tot, where J_tot = J_R + |J_ϕ| + J_z. HE2159-0551 again appears within the Wukong region.