For years, scientists have been scanning the icy outskirts of our Solar System for an unknown massive planet. The ...

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.

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.

No telescope has basked in the night sky quite like the enormous new Vera Rubin Observatory. Here's what it could reveal ...

A Planet Nine probe would have to travel further than NASA's Voyager 1 space probe. (Image credit: NASA/JPL-Caltech) Seventy-five years may seem like a long time for a one-way trip.

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.

Nicknamed "Planet Nine," the real-life Planet X appears to have the mass of 10 Earths and is 20 times farther from the sun than Neptune. Skip to main content. Open menu Close menu.

A new look through decades-old data has unveiled some of the most compelling evidence yet of a hidden ninth planet in the far reaches of our solar system, far beyond ...

If Planet 9 exists, a similar scenario may have played out in the early days of our Solar System, with Jupiter's gravity pushing it toward the edge, only for it to be saved by another, alien star.

But hunting down a specific object such as Planet Nine is a whole different exercise. "There's only one tiny portion of the sky that has it," says Batygin, ...

If Planet 9 is on the smaller side, dark, and really far away, he explains, "it's going to be on the edge of Vera Rubin detection, and Vera Rubin may not find it." ...