Hunt for Planet Nine heats up.

Abstract

Several teams are racing to spot Planet Nine, a hypothetical giant planet in the outer reaches of the solar system, based on the way it may have shepherded six objects into clustered orbits. Studies presented last week at a meeting of the American Astronomical Society are giving them extra encouragement. Researchers have found new objects that fit in with the clustering of the original six, as well as other oddballs that orbit nearly perpendicular to the solar system. The influence of the unseen giant may even be responsible for tipping the sun slightly on its axis. Using large telescopes with wide-field cameras, the teams are starting to rule out parts of the sky in which they think the planet lurks.