For years, astronomers have searched for evidence of a hidden giant planet at the edge of our solar system. New data suggests ...

A new study suggests the existence of Planet Y. This hidden planet may be affecting the Kuiper Belt. The gravity of Planet Y could be causing a tilt in the orbits of some icy objects. Researchers ...

New discoveries of objects in the Kuiper Belt have also presented challenges for the Planet Nine theory. The latest is known ...

Astronomers propose a new hypothetical planet, Planet Y, beyond Neptune, based on observed orbital anomalies in the Kuiper ...

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.

Yet actually finding Planet Nine, sometimes called Planet X, has eluded scientists for nearly a decade. But the hunt for the solar system's potential ninth planet may soon be coming to a close.

If their calculations serve them correctly, Planet Nine would have a mass that is about 1.5 to 3 times that of Earth, at 500 times the distance between our home and the sun. Caltech researchers in ...

As a result, a Planet Nine probe would have to travel around three times faster than Voyager 1 to reach Planet Nine in the researcher's timeframe. This may seem unlikely but it is possible, Lingam ...

Planet Nine should be detectable by that telescope. But it would require an adjustment in the planned observing protocol to extend the telescope’s survey farther north than planned, Brown says ...

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.

And no, we're not talking about Pluto, which was demoted from full planetary status to "dwarf planet" in 2006. Instead, scientists believe Planet Nine is a gas or ice giant billions of miles ...