Astronomers have had their sights set beyond Neptune for decades, hoping to find an elusive heavyweight dubbed “Planet Nine.” This hypothetical planet, if it exists, could account for the strange orbits of objects on the outskirts of our solar system, ...

After a fresh hunt, there was still no sign of the mysterious Planet Nine in the distant solar system. As of yet, the speculative planet has escaped discovery; nevertheless, a six-year hunt at millimeter wavelengths has enabled researchers in the ...