A triple-induced merger in solves the proplyd lifetime problem and the curiously young shell of M42
Year: 2026
Type: article
Abstract: A longstanding tension exists between the stellar ages in the Orion Nebula Cluster (ONC) and the rapid external photoevaporation of its protoplanetary discs. More recently, the shell of the Orion Nebula has also been found to be dynamically younger than its stars. We propose a new scenario aimed at resolving both age issues. In our scenario, the most massive star of the ONC, formed from the merger between two binary stars induced by von Zeipel-Lidov-Kozai oscillations due to the present-day binary companion This merger, taking place between the last episode of star formation and today, resulted in an increased luminosity, leading to stronger external photoevaporation and accelerated expansion of the shell. We used Monte Carlo simulations to explore both whether a sudden brightening of could reconcile the stellar ages and shell expansion. We also considered whether the assumption of triple progenitors for could result in stellar mergers on the relevant timescale. A sudden brightening of a few hundred thousand years ago can be effective in reproducing today's shell, while maintaining a system age close to the stellar age. However, the required increase in the stellar wind luminosity would be greater than a simple merger would be equipped to explain. At a lower luminosity, the mixing of a relatively greater amount of cool photoevaporative wind material into the hot bubble could result in the required increase, and we identified a lower limit on the required strength of this effect. Additionally, we find that progenitor triples merge readily on timescales that are even shorter than the scenario would require. These mergers could be deferred by increased pre-main sequence tidal effects, rotation, and perturbing encounters with other cluster members. Ultimately, our proposed scenario with a merger driven by von Zeipel-Lidov-Kozai evolution successfully resolves two issues: the Orion Nebula's proplyd problem and the shell lifetime problems.
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7221348327