Planet X has a long and storied history of non-existence. For about 130 years, astronomers have debated the existence of an additional planet or planets to explain discrepancies in the orbits of ...

In an exciting breakthrough in planetary science, a recent study has increased the likelihood of Planet Nine’s existence by up to 40%. This planet, also referred to as Planet X, has remained an ...

Planet X, or Nibiru, is on a crash course with Earth, doomsayers believe — prophecies draw new focus with ‘Planet Nine’ discovery ...

Scientists may have discovered a dwarf planet far beyond Neptune — an unearthing that may disprove a longstanding theory about the possibility of a giant ninth planet. The dwarf planet's existence ...

For the dwarf planet candidate, one trip around the sun takes over 24,000 years. Its orbit challenges a proposed path for a hypothetical Planet Nine.

While searching for the mysterious Planet X that some astronomers believe lurks on the edge of our solar system, researchers instead found an extremely distant object they dubbed “the Goblin.” ...

An artist's concept of Planet 9, sometimes referred to as Planet X. Planet 9 is a hypothesized ninth planet in our solar system. It is not about to kill us all.

Planet X, or Planet Nine as it has also been called, is a theoretical planet that some astronomers think could be hiding at the very edge of our solar system.

And if Planet X — also sometimes called Planet Nine — exists, it’s way out there; it’s somewhere between 200 and 1,200 times the distance from the Sun to Earth.

Although the paper is certain to revive the search for Planet X, success is not certain: Previous surveys have failed to detect any Saturn-sized planets going out as far as 10,000 AU.

If Planet X is out there, it’s really, really far away. Brown and Batygin’s educated guess as to where Planet X might be is based on the crooked orbits of 6 very distant objects.

If there is a Planet X out there, it will necessitate a wholesale rewriting of some key chapters of the solar system's history. On the trail of hidden worlds.