ELI5: Explain Like I'm 5

Fifth planet (hypothetical)

Imagine if there was another planet out there, far far away from us, that we have never seen or discovered yet. Scientists believe that there might be a fifth planet in our solar system, but they are not sure yet because they have not found any evidence for it.

You see, we have four planets in our solar system that we can see with our eyes or telescopes: Mercury, Venus, Earth, and Mars. But scientists think that there might be one more planet beyond our furthest planet, Neptune. This planet is so far away and so hard to see that we need special equipment and telescopes to look for it.

Scientists call this hypothetical fifth planet "Planet Nine" or "Planet X." They think it might be a giant planet, larger than Earth, but smaller than Neptune. It could take 10,000 to 20,000 years for this planet to make one orbit around our sun, which is why it is so hard to find.

Scientists believe that the existence of this planet could explain some strange behavior of objects in our solar system. They have seen some objects in space that are orbiting in a strange way, and they think the gravitational pull of this hypothetical fifth planet might be causing it.

But until we have more evidence, this fifth planet remains a mystery. Scientists will continue to study our solar system and use advanced technology to search for any clues that might lead them to find this planet someday.