In the version of this Letter originally published, the Author Contributions section was mistakenly omitted, and should have read: “G.M.K. conceived the project, analysed the data, carried out the modelling and wrote the manuscript. L.M. contributed gas calculations and provided advice on self-calibration. B.M.Y. set up and ran the n-body simulations. D.P. provided advice on running the smoothed particle hydrodynamics simulations. All co-authors provided input on the manuscript.” In addition, in the fourth paragraph, due to a typographical error the value of the ascending node was incorrect as 289 ± 1° and should have been 337.6 ± 2.4°. These errors have now been corrected.