Abstract

Observational campaigns, over the last two decades, have revealed a new mystery related to our own Solar System. As it turns out, icy bodies orbiting the Sun beyond the orbit of Neptune exhibit unexpected orbital architecture. Specifically, observations have unveiled that a subset of such small bodies – known as trans-Neptunian objects – have their orbits spatially clustered. Such spatially clustered configurations can not be explained by the current eight-planet Solar System architecture. This has led to the so-called “Planet Nine” hypothesis: a yet undiscovered super-Earth resides in the distant Solar System inducing, and maintaining, the puzzling orbital configurations. In this talk, I will first explain the observational signatures which promoted the aforementioned “Planet Nine” hypothesis. I will then put forward an alternative which could obviate the need for “Planet Nine”. Specifically, I will demonstrate how the gravitational effects of a relatively massive population of trans-Neptunian objects can naturally provide an explanation for the observed spatial clustering.