What If Planet Nine Has Satellites?

Abstract

In the past decade, numerical simulations started to reveal the possible existence of Planet Nine in our solar system. The Planet Nine scenario can provide an excellent explanation for the clustering in orbital elements for Kuiper Belt objects. However, no optical counterpart has been observed so far to verify the Planet Nine scenario. Therefore, some recent studies suggest that Planet Nine could be a dark object, such as a primordial black hole. In this article, we show that the probability of capturing large trans-Neptunian objects by Planet Nine to form a satellite system in the scattered disk region (between the inner Oort Clouds and the Kuiper Belt) is large. By adopting a benchmark model of Planet Nine, we show that the tidal effect can heat up the satellites significantly, which can give sufficient thermal radio flux for observations, even if Planet Nine is a dark object. This provides a new, indirect way for examining the Planet Nine hypothesis and revealing the basic properties of Planet Nine.