Observational constraints on an undiscovered giant planet in our solar system

Over the last few years, the action of an undiscovered giant planet has been considered in many works to explain the orbital properties of the most distant known objects in our solar system. Despite the great interest in the hypothesized planet, the observational evidence for it still remains in question with some works suggesting it is statistically significant and some works suggesting it is not. We review the current observational evidence for the planet, which consists primarily of an observed orbital alignment of the most distant Trans-Neptunian objects and inner Oort cloud objects. We will discuss observational biases in differing survey types and how they might affect the observed population. We will also discuss how to best detect such a planet and summarize the current state of wide-field observational surveys that are sensitive to the hypothesized planet. Over the next few years, similar surveys have a good chance at discovering the hypothesized and are likely to double the population of distant Trans-Neptunian objects and inner Oort cloud objects, which will provide additional insights into the hypothesized planet scenario.