A close-in giant planet escapes engulfment by its star
Abstract
When main-sequence stars expand into red giants, they are expected to engulf close-in planets. Until now, the absence of planets with short orbital periods around post-expansion, core-helium-burning red giants has been interpreted as evidence that short-period planets around Sun-like stars do not survive the giant expansion phase of their host stars. Here we present the discovery that the giant planet 8 Ursae Minoris b orbits a core-helium-burning red giant. At a distance of only 0.5 au from its host star, the planet would have been engulfed by its host star, which is predicted by standard single-star evolution to have previously expanded to a radius of 0.7 au. Given the brief lifetime of helium-burning giants, the nearly circular orbit of the planet is challenging to reconcile with scenarios in which the planet survives by having a distant orbit initially. Instead, the planet may have avoided engulfment through a stellar merger that either altered the evolution of the host star or produced 8 Ursae Minoris b as a second-generation planet. This system shows that core-helium-burning red giants can harbour close planets and provides evidence for the role of non-canonical stellar evolution in the extended survival of late-stage exoplanetary systems.
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Cite
@article{arxiv.2306.15877,
title = {A close-in giant planet escapes engulfment by its star},
author = {Marc Hon and Daniel Huber and Nicholas Z. Rui and Jim Fuller and Dimitri Veras and James S. Kuszlewicz and Oleg Kochukhov and Amalie Stokholm and Jakob Lysgaard Rørsted and Mutlu Yıldız and Zeynep Çelik Orhan and Sibel Örtel and Chen Jiang and Daniel R. Hey and Howard Isaacson and Jingwen Zhang and Mathieu Vrard and Keivan G. Stassun and Benjamin J. Shappee and Jamie Tayar and Zachary R. Claytor and Corey Beard and Timothy R. Bedding and Casey Brinkman and Tiago L. Campante and William J. Chaplin and Ashley Chontos and Steven Giacalone and Rae Holcomb and Andrew W. Howard and Jack Lubin and Mason MacDougall and Benjamin T. Montet and Joseph M. A. Murphy and Joel Ong and Daria Pidhorodetska and Alex S. Polansk and Malena Rice and Dennis Stello and Dakotah Tyler and Judah Van Zandt and Lauren Weiss},
journal= {arXiv preprint arXiv:2306.15877},
year = {2023}
}
Comments
Published in Nature on 28 June 2023. In press