There is no new planet discovered in our solar system that is officially recognized as a planet. The last planet discovered in our solar system was Pluto, which was discovered in 1930. However, it was reclassified as a dwarf planet in 2006.

While there have been many exoplanets discovered outside of our solar system, it's difficult to say definitively which is the "newest" as new discoveries are constantly being made.

If you're interested in learning more about exoplanets, I recommend checking out resources like the NASA Exoplanet Archive or the European Space Agency's website.