Astronomers Search for Planet Nine in the Outer Solar System

Imagine our solar system is like a big backyard.

We know about the Sun and the planets that play close to it, like Earth and Mars.

Neptune is the last of these known planets.

Beyond Neptune, there's a huge, cold, and dark area filled with icy rocks, kind of like a backyard shed full of old toys from when the solar system was built.

Pluto used to be called a planet, but scientists decided it's more like a toy in that shed, so now it's called a dwarf planet.

Some scientists think there might be an even bigger, hidden planet out there, far beyond Neptune, called Planet Nine.

They believe its gravity might be making some of the icy toys in the shed move in a funny way.

No one has seen this Planet Nine yet, but scientists are using powerful new tools to look for it.

They are also still exploring the icy shed to find more hidden worlds.