  The orbits of trans-Neptunian objects (TNOs) can indicate the existence of an
undiscovered planet in the outer solar system. Here, we used N-body computer
simulations to investigate the effects of a hypothetical Kuiper Belt planet
(KBP) on the orbital structure of TNOs in the distant Kuiper Belt beyond ~50
au. We used observations to constrain model results, including the
well-characterized Outer Solar System Origins Survey (OSSOS). We determined
that an Earth-like planet (m ~ 1.5-3 Earth masses) located on a distant
(semimajor axis a ~ 250-500 au, perihelion q ~ 200 au) and inclined (i ~ 30
deg) orbit can explain three fundamental properties of the distant Kuiper Belt:
a prominent population of TNOs with orbits beyond Neptune's gravitational
influence (i.e., detached objects with q > 40 au), a significant population of
high-i objects (i > 45 deg), and the existence of some extreme objects with
peculiar orbits (e.g., Sedna). Furthermore, the proposed KBP is compatible with
the existence of identified Gyr-stable TNOs in the 2:1, 5:2, 3:1, 4:1, 5:1, and
6:1 Neptunian mean motion resonances. These stable populations are often
neglected in other studies. We predict the existence of an Earth-like planet
and several TNOs on peculiar orbits in the outer solar system, which can serve
as observationally testable signatures of the putative planet's perturbations.
