The Kuiper belt is a population of icy bodies beyond the orbit of Neptune . A particularly puzzling and up-to-now unexplained feature of the Kuiper belt is the so-called ‘ kernel ’ , a concentration of orbits with semimajor axes a \simeq 44 AU , eccentricities e \sim 0.05 , and inclinations i < 5 ^ { \circ } . Here we show that the Kuiper belt kernel can be explained if Neptune ’ s otherwise smooth migration was interrupted by a discontinuous change of Neptune ’ s semimajor axis when Neptune reached \simeq 28 AU . Before the discontinuity happened , planetesimals located at \sim 40 AU were swept into Neptune ’ s 2:1 resonance , and were carried with the migrating resonance outwards . The 2:1 resonance was at \simeq 44 AU when Neptune reached \simeq 28 AU . If Neptune ’ s semimajor axis changed by fraction of AU at this point , perhaps because Neptune was scattered off of another planet , the 2:1 population would have been released at \simeq 44 AU , and would remain there to this day . We show that the orbital distribution of bodies produced in this model provides a good match to the orbital properties of the kernel . If Neptune migration was conveniently slow after the jump , the sweeping 2:1 resonance would deplete the population of bodies at \simeq 45-47 AU , thus contributing to the paucity of the low-inclination orbits in this region . Special provisions , probably related to inefficiencies in the accretional growth of sizable objects , are still needed to explain why only a few low-inclination bodies have been so far detected beyond \simeq 47 AU .