Since 2006, when Pluto was stripped of its planetary status, the solar system has had eight planets. However, the strange alignment of certain trans-Neptunian objects raises questions for some: what if there were a ninth planet hidden somewhere?
Since Pluto was downgraded to dwarf planet status, our solar system has only had eight planets. But perhaps a ninth is hiding at the edge of our system: the hypothetical Planet 9. Where are we in the search for it?
For 10 years, this hypothesis has been firing the imagination. Also known as Planet X, it would be the fifth largest planet in the solar system, located in a very distant orbit, far beyond Neptune, and would take 20,000 years to orbit the sun. It would explain the unusual trajectories and configuration of certain trans-Neptunian objects. A decade later, we still haven’t found it. If it does exist, questions remain. Where and how can we hunt for it? And if it doesn’t exist, what does this controversy teach us about the scientific method?