Here's why:

* Our Solar System: We currently recognize eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

* Dwarf Planets: There are also several dwarf planets, including Pluto, Eris, Makemake, and Haumea.

* No More Planets: Astronomers haven't discovered any additional objects that meet the criteria for being classified as a full-fledged planet.

So, while there might be other undiscovered objects beyond Neptune, there is no "126th planet" in our solar system.