Is there a massive undiscovered planet on the outer reaches of the solar system? The idea has been around since before the ...

Astronomers are closing in on evidence that a massive, unseen planet may exist far beyond Neptune. This discovery could ...

Researchers use the Subaru Telescope in Hawaii to find a small object on the outer edge of the Solar System. Nicknamed ...

A newly discovered dwarf planet called 'Ammonite' (2023 KQ14) has been spotted in the outer solar system, and it could be ...

Astronomers have found 2023 KQ14, nicknamed Ammonite, a rare sednoid with a unique orbit that challenges the Planet Nine ...

Planet Nine's composition is probably "most like Neptune," due to its distance from the sun, Brown said. "That would put its diameter at something like two times the width of Earth," he added.

Planet Nine (illustrated) is a hypothetical giant planet hiding at the solar system’s edge — but new work suggests the evidence for it is a mirage. ESA/Hubble, M. Kornmesser By Lisa Grossman ...

Planet Nine should appear stationary over the course of a single day but show detectable movement over months.

But he adds that “if Planet Nine is not out there, we need a separate explanation for each of these other things, that can all be explained by a single Planet Nine.

If Planet 9 is real, this observatory has around a 70 to 80 percent chance of finding it, he estimates, adding that it's not a sure thing because there are so many uncertainties.