Asteroids with diameters less than about 5 km have complex histories because they are small enough for radiative torques (that is, YORP, short for the Yarkovsky–O’Keefe–Radzievskii–Paddack effect)¹ to be a notable factor in their evolution². (152830) Dinkinesh is a small asteroid orbiting the Sun near the inner edge of the main asteroid belt with a heliocentric semimajor axis of 2.19 au; its S-type spectrum^3,4 is typical of bodies in this part of the main belt⁵. Here we report observations by the Lucy spacecraft^6,7 as it passed within 431 km of Dinkinesh. Lucy revealed Dinkinesh, which has an effective diameter of only 720 m, to be unexpectedly complex. Of particular note is the presence of a prominent longitudinal trough overlain by a substantial equatorial ridge and the discovery of the first confirmed contact binary satellite, now named (152830) Dinkinesh I Selam. Selam consists of two near-equal-sized lobes with diameters of 210 m and 230 m. It orbits Dinkinesh at a distance of 3.1 km with an orbital period of about 52.7 h and is tidally locked. The dynamical state, angular momentum and geomorphologic observations of the system lead us to infer that the ridge and trough of Dinkinesh are probably the result of mass failure resulting from spin-up by YORP followed by the partial reaccretion of the shed material. Selam probably accreted from material shed by this event.

直径小于约 5 公里的小行星具有复杂的历史，因为它们足够小，辐射扭矩（即 YORP，Yarkovsky-O'Keefe-Radzievskii-Paddack 效应的缩写） ¹成为其演化中的一个显着因素² 。 (152830) 丁基内什 (Dinkinesh) 是一颗小型小行星，靠近主小行星带内缘，绕太阳运行，日心半长轴为 2.19 au ；其S型光谱^3,4是主带⁵这部分中的典型天体。在此，我们报告了露西号航天器^6,7在经过丁基内什 431 公里范围内时的观测结果。 Lucy透露Dinkinesh的有效直径只有720 m，其复杂程度出人意料。特别值得注意的是，存在一个突出的纵向槽，上面覆盖着一个巨大的赤道脊，并且发现了第一颗已确认的接触双星卫星，现在命名为（152830）Dinkinesh I Selam。 Selam 由两个大小几乎相等的波瓣组成，直径分别为 210 m 和 230 m。它绕丁基内什轨道运行，距离为3.1公里，轨道周期约为52.7小时，并被潮汐锁定。系统的动力学状态、角动量和地貌观察使我们推断，丁基什星系的脊和谷可能是由 YORP 旋转上升和棚物质部分再吸积导致的质量破坏的结果。塞拉姆可能是由这次事件所脱落的物质堆积而成的。