Catching a planet: A tidal capture origin for the exomoon candidate Kepler 1625b I
Adrian S. Hamers, Simon F. Portegies Zwart
(Submitted on 25 Oct 2018)
The (yet-to-be confirmed) discovery of a Neptune-sized moon around the 17.2 Jupiter-mass planet in Kepler 1625 puts interesting constraints on the formation of the system. In particular, the relatively wide orbit of the moon around the planet, at ~40 planetary radii, is hard to reconcile with planet formation theories. We demonstrate that the observed characteristics of the system can be explained from the tidal capture of a secondary planet in the young system. After a quick phase of tidal circularization, the lunar orbit, initially much tighter than 40 planetary radii, subsequently widened gradually due to tidal synchronization of the spin of the planet with the orbit, resulting in a synchronous planet-moon system. Interestingly, in our scenario the captured object was originally a Neptune-like planet, turned into a moon by its capture.
Comments: Submitted to ApJL. 6 pages, 5 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1810.11060 [astro-ph.EP] (or arXiv:1810.11060v1 [astro-ph.EP] for this version)
Submission history
From: Adrian Hamers
[v1] Thu, 25 Oct 2018 18:31:45 UTC (757 KB)
