Macquarie University
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3D hydrodynamic simulations of large-planet engulfments by a red giant star

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posted on 2022-10-18, 00:56 authored by Stephen NeilsonStephen Neilson

As planetary systems are now known to be common, it is inevitable that planets orbiting near their host star may be enveloped by the star as it evolves. What happens after this, to both the star and planets, is subject to much discussion based on both theory and observational evidence. This thesis explores this scenario using two computerized hydrodynamic simulations involving a 0•.77 M , 166 R red giant star engulfing 10 Mj planets. One simulation involves a single planet (inner) and the other involves two planets (inner and outer). The thesis finds that the presence of the outer planet has little effect on the inner planet’s in-spiral path. This thesis also finds that the in-spiral of the planets has significant impacts on the star’s shape and size, with it leading to an increase of the star’s diameter by as much as 80%. Various patterns of gas flow are induced inside the star, and the star’s final surface velocity, contrary to expectations, is smaller in magnitude and less uniform than expected. It is concluded that in real life that the planets would be destroyed by their in-spiral despite technical limitations preventing their destruction in the simulations.


Table of Contents

1. Introduction -- 2. Methods -- 3. Results: planet orbital effects and fate -- 4. Results: effects on stellar geometry and gas flow -- 5. Conclusion -- A. Appendix -- References


A thesis submitted to Macquarie University for the degree of Master of Research

Awarding Institution

Macquarie University

Degree Type

Thesis MRes


Thesis (MRes), Macquarie University, Faculty of Science and Engineering, 2021

Department, Centre or School

Department of Physics and Astronomy

Year of Award


Principal Supervisor

Orsola De Marco


Copyright: Stephen Neilson Copyright disclaimer:




67 pages