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.

Scientists may have discovered a dwarf planet far beyond Neptune — an unearthing that may disprove a longstanding theory ...

But it's far more likely for astronomers combing the cosmos for signs of extraterrestrial life to eventually stumble upon a habitable planet that ... stars outside our solar system.

However, this year a powerful new telescope is coming online that could prove once and for all that there really is a ninth planet in our Solar System. The same year that Pluto was ignominiously ...

One set of dots had matching colors and brightness. open image in gallery Is there a possible ninth planet in our solar system? Researchers say they may have found a candidate (Credit: ESO/Tom ...

Pluto was reclassified as a dwarf planet in 2006. Our solar system may have a ninth planet after all, researchers say. The possibility that an additional planet may be hidden far into the solar ...

Check out the rest of the series. If you were born in the last century you might have memorized that there were nine planets in our solar system, as heard in the famous Schoolhouse Rock!

So, during the summer of 2006, members of the International Astronomical Union convened in Prague to reconsider what counts as a planet in our solar system. IAU members decided that there were ...