Kuiper Belt Planet Simulation Indicates Undiscovered Planet in Outer Solar System

Tuesday - September 5 2023, 07:21 UTC - 1 year ago

Computer simulations of trans-Neptunian objects (TNOs) suggest the existence of an as-yet undiscovered Kuiper Belt Planet (KBP) 1.5 - 3 times the mass of Earth in the outer solar system. The proposed KBP is compatible with the existence of stable resonant TNO populations in the distant Kuiper Belt, and its perturbations can explain the distribution of detached, high-inclination, and extreme TNOs. Further observation of the Kuiper Belt may reveal or rule out the existence of the KBP.

Japanese researchers have used computer simulation and the orbits of several large objects past Neptune to calculate that there is Kuiper Belt planet 1.5–3 times as massive as Earth, located at ten to twenty times further than Neptune (250–500 au). There must be a prominent population of detached TNOs, well decoupled from Neptune; a significant fraction of high-i TNOs with i > 45°; and a subpopulation of detached or high-i extreme TNOs evolving on peculiar orbits. The proposed KBP is compatible with the existence of long-term gigayear-stable resonant TNOs, and its perturbations do not preclude the formation of scattering populations with q < 40 au. Finally, the scenario's resulting orbital structure beyond ∼50 au is reasonably compatible with the inclination and perihelion distributions of OSSOS and other observational constraints.

In conclusion, the results of the KBP scenario support the existence of a yet-undiscovered planet in the far outer solar system. Furthermore, this scenario also predicts the existence of new TNO populations located beyond 150 au generated by the KBP's perturbations that can serve as observationally testable signatures of the existence of this planet. More detailed knowledge of the orbital structure in the distant Kuiper Belt can reveal or rule out the existence of any hypothetical planet in the outer solar system. The existence of a KBP may also offer new constraints on planet formation and dynamical evolution in the trans-Jovian region.

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 M⊕) located on a distant (semimajor axis a ∼ 250–500 au, perihelion q ∼ 200 au) and inclined (i ∼ 30°) 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°), and the existence of some extreme objects with peculiar orbits (e.g., Sedna). Furthermore, the proposed KBP is compatible with the existence of identified gigayear-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.