Abstract
When main-sequence stars expand into red giants, they are expected to engulf close-in planets 1–5. Until now, the absence of planets with short orbital periods around post-expansion, core-helium-burning red giants 6–8 has been interpreted as evidence that short-period planets around Sun-like stars do not survive the giant expansion phase of their host stars 9. Here we present the discovery that the giant planet 8 Ursae Minoris b 10 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 11. 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.
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Nature |
| Vol/bind | 618 |
| Nummer | 7967 |
| Sider (fra-til) | 917-920 |
| Antal sider | 4 |
| ISSN | 0028-0836 |
| DOI | |
| Status | Udgivet - jun. 2023 |