Growing up, I was taught that there were nine planets in the solar system. That all changed in 2006, when the International Astronomical Union voted to demote Pluto's status to that of dwarf planet.

For nearly a decade, astronomers have been searching for a hypothetical giant planet that may lurk in the distant reaches of the solar system. We could be on the brink of discovering this new world, ...

Known as Planet Nine or Planet X, it is a hypothetical planet that has long been rumoured to exist in the outer solar system. Although "several claims to have found an extra planet have been made ...

Planet Nine, a massive icy world, may be lurking at the outer edge of our solar system, awaiting discovery by advanced telescopes. "It's really difficult to explain the solar system without Planet ...