What if Planet 9 is a Primordial Black Hole?
  We highlight that the anomalous orbits of Trans-Neptunian Objects (TNOs) and
an excess in microlensing events in the 5-year OGLE dataset can be
simultaneously explained by a new population of astrophysical bodies with mass
several times that of Earth ($M_\oplus$). We take these objects to be
primordial black holes (PBHs) and point out the orbits of TNOs would be altered
if one of these PBHs was captured by the Solar System, inline with the Planet 9
hypothesis. Capture of a free floating planet is a leading explanation for the
origin of Planet 9 and we show that the probability of capturing a PBH instead
is comparable. The observational constraints on a PBH in the outer Solar System
significantly differ from the case of a new ninth planet. This scenario could
be confirmed through annihilation signals from the dark matter microhalo around
the PBH.
